A Window to Unitization and Other Cognitive Processes in Reading Text

Psychonomic Bulletin & Review /994. / (3). 333-344

Letter detection: A window to unitization and other cognitive processes in reading text

ALICE F. HEALY University ofColorado, Boulder, Colorado

Experiments are reviewed that use the letter-detection task, in which subjects read text and cir cle target letters. Evidence is provided that the letter-detection task reveals the processing units used in reading text and is influenced as well by visual, phonetic, and a combination of semantic and syntactic factors. Specifically, it is shown that circling a target letter in a word depends on the familiarity of the word's visual configuration, the location of the word in the reader's visual field, the phonetic representation of the letter in the word, and a combination of the word's meaning and its grammatical function.

For the past two decades my colleagues and I have been letter identification. The identification of these higher using a very simple letter-detection task to study the order units is facilitated by familiarity; for example, cognitive processes involved in reading text. Our earlier common words are identified as units more easily than work with this task illuminated the basic processing units rare words. It is also proposed that once a larger unit is used in reading text (see Healy, 1981a, for a summary). identified, the processing of its component letter units Our more recent research with the same task, although is terminated, even if the letters have not yet reached the continuing to support the importance ofprocessing units, point ofidentification. Instead, processing and attention has examined a broader spectrum ofcognitive processes are directed to the next location in the text. Because let and has consequently thrown light on visual, phonetic, ter identification is not always completed for highly fa and a combination ofsemantic and syntactic factors that miliar words such as the, many letter-detection errors are influence letter- and word-identification processes in read made on those words. ing. In this article, I begin by reviewing some ofthe ear It has been argued that the letter-detection task dis lier work on unitization and then review some of the torts the normal processes used in reading (see, e.g., more recent studies highlighting the importance ofother Rayner & Pollatsek, 1989). Following from the obser cognitive processes. vation that letter detection poses an additional require ment (circling target letters) superimposed on the normal Unitization reading task, this argument is that such a requirement The basic letter-detection task we have been using is may alter the processing units employed by the readers. illustrated in Table 1 with a 1OO-word passage from Gold However, it has been demonstrated under different cir ing (1959). One striking finding from this task is that cumstances that it is difficult for subjects to disengage subjects make an extremely large number of errors on the their normal reading responses even when a laboratory word the. Drewnowski and Healy (1977) proposed a set task demands that they do so (see, e.g., MacLeod, 1991; of hypotheses, referred to as the unitization hypotheses, Stroop, 1935). Further, it has been shown that the missing to account for this "missing-letter" effect. According to letter effect is, if anything, increased when subjects are these hypotheses, we can use featural information to given explicit instructions to comprehend the material identify supraletter units, such as syllables, words, or even they are reading (e.g., Proctor & Healy, 1985; Smith & short phrases, without necessarily having to complete Groat, 1979) and that the missing-letter effect is de creased or reversed when subjects are prevented from using their normal left-to-right reading pattern (e.g., Preparation ofthis article was supported in part by Army Research Drewnowski & Healy, 1977; Hadley & Healy, 1991; Institute Contract MDA903-93-K-00IO to the University ofColorado. Healy, Oliver, & McNamara, 1987). I am grateful to Bob Crowder, Betty Ann Levy, an anonymous reviewer, Initial experiments. In an initial series ofexperiments and especially Jim Neely for very helpful and thoughtful comments concerning earlier versions ofthis article, which is based on an invited (Healy, 1976), I tried to distinguish between the uniti presentation at the 1991 meeting of the American Psychological As zation hypotheses and three reasonable alternative ex sociation, never delivered due to my sustaining a ruptured appendix. I planations for the missing-letter effect, which I have would like to take this opportunity to express my deepest gratitude to termed the location, pronunciation, and redundancy hy my surgeon, Dr. John Day, for saving my life at that time. Correspon potheses. According to the location hypothesis, subjects dence should be sent to the author at the Department of Psychology, Muenzinger Building, University of Colorado, Campus Box 345, miss the t in the because of its location at the start of a Boulder, CO 80309-0345 (e-mail: [email protected]). three-letter word. The pronunciation hypothesis accounts

Table 1 prose passage was greater than that on the scrambled Instructions and Sample Passage for Letter Detection Task letter passage, but the reading time was shorter on prose Instructions than it was on scrambled letters. Hence, there is a speed Yourtask is to read the passage below at your normal reading speed, accuracy trade-off in this task.' For that reason it is not but whenever you come to a letter t, encircle it with your pen or pen wise to compare the absolute proportions oferrors made cil. If at any time you realize that you missed a t in a previous word, on ts in the locations in the two passages, although those do not retrace your steps to encircle the t. Youare not expected to get every t, so do not slow down your reading speed in order to be over proportions are given in Table 3. However, the condi cautious about getting the ts. tional proportion of errors in the locations given that an Passage error was made should not be influenced by any speed Smoke was rising here and there among the creepers that festooned accuracy trade-off. This measure is also shown in Table3. the dead or dying trees. As they watched, a flash of fire appeared at The mean conditional proportion of errors expected on the root of one wisp, and then the smoke thickened. Small flames the basis ofchance alone is .275, because there were 40 stirred at the bole ofa tree and crawled away through leaves and brush ts altogether and 11 of them occurred in the locations. wood, dividing and increasing. One patch touched a tree trunk and Although the conditional proportion of errors in the scrambled up like a squirrel. The smoke increased, sifted, rolled out wards. The squirrel leapt on the wings of the wind and clung to an prose passage was much greater than chance, in the other standing tree, eating downwards. The fire laid hold on the for scrambled-letter passage it was below the chance level, est and began to gnaw. [Golding, 1959 (pp. 56-57)] contrary to the location hypothesis prediction. In Experiment 2 (Healy, 1976), Corcoran's (1966) re dundancy hypothesis was tested. To do so, I constructed for the large number of errors on the in terms of the a scrambled-word passage, which was the same as the somewhat atypical pronunciation ofthe t: Perhaps sub prose passage except for the arrangement ofthe words. jects searching for ts scan a phonetic representation of the passage, formed by phonological recoding; if so, it Table 2 would be reasonable to expect them to miss ts that are Sample Text from Various Experiments not pronounced in the usual fashion. This hypothesis is 1. Healy, 1976: consistent with the results of a classic experiment re Experiment 1 ported by Corcoran (1966), who found that subjects Prose: Smoke was rising here and there among the searching for the letter e in a magazine article missed Scrambled Letters: Irwsa eek dmenna ross igh tmaen esarr thp more silent es (such as the e in take) than pronounced es Experiment 2 Scrambled Words: Rising tree root watched wings laid of the (such as the es in elephant). The third alternative expla Experiment 3 nation for the missing-letter effect-the redundancy hy Thy: Rising tree root watched wings laid of thy pothesis-was first proposed by Corcoran (1966), and Experiment 4 refers to the semantic and syntactic redundancy, or pre Frequency: Valley history ocean kine mirage gender truce dictability, ofthe word the in normal prose. Specifically, 2. Healy & Drewnowski, 1983: Corcoran, who had found that subjects were more likely Even flowers in the park withered and became leatehry to miss the e in the than they were even to miss silent es, 3. Healy, Oliver, & McNamara, 1987: suggested that the word the may be '''taken for granted' She flicked her hrist and drew her hand from Doctof Harry's and thus not scanned" (p. 658). With normal prose text, 4. Hadley & Healy, 1991: a reader should be able to anticipate when the word the 5-letter window: I the I would occur on the basis ofthe surrounding word con I5-letter window: Ithen the smoke I text, and thus might skip over that word in order to pay 5. Schneider, Healy, & Gesi, 1991: more attention to words that provide more information. Experiment 1 In Experiment 1 (Healy, 1976), the location hypothe Normal: Finished files are the result of years of scientific study sis was tested by comparing subjects' performance on combined with the experience ofyears. Asterisk: *F*i*n*i*s*h*e*d* *f*i*l*e*s* *a*r*e* *t*h*e* two passages. For each passage, subjects were given in *r*e*s*u*l*t* *o*f* *y*e*a*r*s* *o*f* *s*c*i*e*n*t*i*f*i*c* structions comparable to those in Table 1 and an identi *s*t*u*d*y* *c*o*m*b*i*n*e*d* *w*i*t*h* *t*h*e* cal prose passage. The scrambled-letter passage differed *e*x*p*e*r*i*e*n*c*e* *o*f* *y*e*a*r*s*.* in one important respect: The letters did not form words, 6. Moravcsik & Healy, in press: but instead were in a scrambled order. In particular, while Experiment 1 the ts, punctuation marks, and interword spaces in this the: Even though it was a Thai dish, all of the ingredients were fa passage were the same as those in the prose passage, the miliar except two: what were the and thong? location ofthe other letters was decided randomly. The thy: Even though it was a Thai dish, all of the ingredients were fa miliar except two: what were thy and thong? first words from these passages are included in Table 2. If the location ofthe letter t were critical, subjects should 7. Moravcsik & Healy, in press: make a disproportionately large number oferrors on the Experiment 2 the definite article: Claiming that the definite article has no mean ts that occur in the word the in the prose passage and on ing and hence is unnecessary, newspapers often omit it in order to those in the corresponding locations ("the locations") in be concise. the scrambled-letter passage. The results are summa the: Claiming that the has no meaning and hence is unnecessary. rized in Table 3. The overall proportion oferrors on the newspapers often omit it in order to be concise. LETTER DETECTION: A WINDOW TO UNITIZATION 335

Table 3 words (.21) than they did on rare words (.16). Although Performance on Prose, Scrambled Letters, and the effect of frequency is not great, it is consistent with Scrambled Words in Study by Healy (1976) the large proportion oferrors on the in the other exper Passage iments, because the is the most frequent word in English Performance Scrambled Scrambled and is considerably more frequent than the nouns used Measure Prose Letters Words as common words in this experiment. Reading time This initial study (Healy, 1976) thus provided evi (in seconds) 47 55 53 p (error) .17 .04 .13 dence in favor ofthe unitization hypotheses and against p (error in the location) .38 .01 .29 the alternative location, pronunciation, and semantic and p (error in the location Ierror) .62 .05 .67 syntactic redundancy hypotheses. It also ruled out an ad ditional alternative explanation of the high error rate on the word the in terms of its within-text repetition (see, The same words were employed, and the punctuation e.g., Kanwisher, 1987) since, although the word the was marks and instances of the word the were kept in the repeated frequently throughout the passage in Experi same locations, but the locations ofthe other words were ment 3, the word thy was repeated the same number of scrambled at random, so that the passage no longer made times but still yielded a low error rate. Likewise, each sense. Hence, in the scrambled-word passage, the word word occurred only once in Experiment 4, but there were the was not predictable on the basis of the surrounding still significantly more errors on common words than word context. The first words are included in Table 2. there were on rare words. This within-text-repetition ex According to the redundancy hypothesis, the conditional planation is also inconsistent with the results from Ex proportion of errors on the word the should be greatly periments 1 and 2 of the study by Moravcsik and Healy reduced in the scrambled-word passage because that (in press), which will be discussed later. word would not be redundant or predictable. The results Although, as reviewed below, subsequent research by are summarized in Table 3. The mean conditional pro myself and my colleagues has provided additional portion oferrors was no less in the scrambled-word pas support for unitization and has continued to refute the sage than it was in the prose passage, contrary to the re specific alternative hypotheses considered in this first dundancy hypothesis prediction. investigation (see, e.g., Healy, 1980; Healy & Drewnow The pronunciation hypothesis was tested in Experi ski, 1983; Proctor & Healy, 1985), our most recent re ment 3 (Healy, 1976), in which a new scrambled-word search has demonstrated the influence of other specific passage was constructed which was identical to the one location factors, pronunciation factors, and a combina used in Experiment 2 except that every instance of the tion ofsemantic and syntactic factors in letter detection. word the was replaced by the word thy. Thy was chosen Other support for unitization. Whereas my first because it is the same length as the, has the letter t in study (Healy, 1976) provided support for the impor the same location, and, most critically, has the letter t tance of word frequency in determining the missing pronounced in the same manner. The first words from letter effect, subsequent studies provided more direct this passage are included in Table 2. In this experiment, evidence for the unitization hypotheses. According to subjects read both scrambled-word passages-the one these hypotheses, subjects should make a large propor with the and the one with thy-in a counterbalanced tion of detection errors on familiar words such as the order. According to the pronunciation hypothesis, sub only when they can use featural information to identify jects should make many errors on thy as well as on the. familiar supraletter units. If the relevant featural infor Contrary to this prediction, the mean conditional pro mation is disturbed so that it does not conform to the fa portion of errors was much lower for thy (.08) than it miliar higher-order unit, letter-detection errors should was for the (.52). diminish. In a set of experiments by Healy and Drew Experiment 4 (Healy, 1976) was aimed at testing the nowski (1983), misspellings and other forms of alter unitization hypotheses, according to which it is the high ation were used to disturb featural information. Only Ex frequency ofthe word the which is critical, because the periment 1 will be reviewed here. ability to process words in units larger than individual In this experiment, we introduced misspellings into a letters should be greatest for the most familiar words. I prose passage by transposing the order ofthe two letters constructed a new scrambled-word passage which in immediately following the target letter. This manipula cluded only nouns, each of which occurred only one tion alters the visual features ofthe words containing the time. The words were selected with the constraint that target letter while preserving the word context and the every common word was paired with a rare word ofthe features of the target itself. We constructed two versions same length. Wherever a t, ifany, occurred in the com of a prose passage. The passage contained instances of mon word, a t occurred in the same location ofthe cor the word the as well as other test words, such as with responding rare word; for example, the common word ered and leathery, which included the letter string the. fact was matched with the rare word pact. The first few In each version of the passage, half of the test words words from this passage are included in Table 2. In ac were misspelled. All misspellings were created by trans cordance with the unitization hypotheses, subjects made posing the hand e following a t. Every test word was a significantly higher proportion of errors on common correctly spelled in one version and misspelled in the 336 HEALY

other. A short segment from one version is included in occurred. In contrast, subjects in our letter-detection Table 2. task read a continuous typewritten text and circle each We found that subjects made many more errors on the instance of a target letter. Hence, at least several words word the than they did on the other test words and that are simultaneously in sight in this letter-detection task. they made more errors on correctly spelled words than A number oftheoretical accounts have been proposed they did on misspelled words. In addition, there was a for the word-superiority effect and the related word significant interaction between these two factors, re frequency advantage. The most influential has been the flecting the fact that the large difference in error pro interactive-activation model proposed by McClelland portions between correctly spelled versions of the and and Rumelhart (1981; Rumelhart & McClelland, 1982). other words (.49 and .08, respectively) was eliminated According to this model, processing occurs in parallel at when they were misspelled (the, .01; other words, .01). the levels of visual features, letters, and words, and ac These results are in line with the unitization hypotheses, tivation at one level leads to excitation or inhibition at because supra letter units should be identified most eas other levels. The important assumption providing for ily for the most common word, the, not so easily for word superiority is the presence of excitatory feedback other correctly spelled words, and hardly at all for all from word units to their component letter units. Whereas misspelled words. this model can thereby account for the facilitating ef This experiment vividly illustrates the importance of fects of familiar contexts on letter identification, it has familiarity in determining letter-detection errors. More no straightforward way in which to account for disrup errors are made both when the target letters are embed tive effects. ded within frequent words and when the words are Unitization hypotheses. In contrast, the unitization hy spelled in their usual manner. Although these effects of potheses discussed earlier provide a framework in which familiarity are robust and easily interpreted, they are both the facilitating and the disruptive effects of famil puzzling insofar as it is generally believed that familiar iarity can be understood. The operation of these hy ity aids, rather than hinders, perceptual processes. There potheses for the reading ofa short segment oftext by a are two lines ofevidence that support the facilitating ef hypothetical subject is illustrated in Figure I. The actual fects offamiliarity in the perception ofprinted text, both input given to the subject is shown at the bottom ofFig of which come primarily from studies employing a ure I, and all the reading units identified by the subject tachistoscopic masking paradigm. The first, the so-called are enclosed in boxes which are placed at different lev "word superiority effect," concerns the superior percep els as a function oftheir size. The particular units iden tion ofletters that occur in words relative to nonword let tified depend on their familiarity to the subject as well ter strings, and was investigated intensively following as on factors specific to the given reading situation. the demonstrations by Reicher (1969) and Wheeler Units can be identified either on the basis ofvisual fea (1970) that controlled for guessing biases. The second tures or as the result ofthe identification ofcomponent line of evidence, the "word-frequency advantage," con lower-level units, as indicated in Figure I by the solid ar cerns the superior perception of words that are frequent rows. The important assumption of the unitization hy in the language relative to those that are less frequent. 2 potheses, which differentiates them from the interactive In contrast to these studies with the masking paradigm activation model, is that once a unit has been identified, demonstrating that letter identification is aided by fa the processing ofits component lower-level units is ter miliar word contexts, our letter-detection task has yielded minated, even if they have not yet reached the point of strong results in the opposite direction. As I have already identification; instead, processing and attention are described, our studies with this task have demonstrated driven to the next location in the text, as indicated in Fig a large proportion of letter-detection errors in correctly ure I by the dashed arrows. Thus, in the example, the spelled words relative to misspelled words (which we subject identifies the common word pair ofthe as a unit have termed the "word-inferiority effect"), as well as in at the supraword level before having identified all ofits frequent words relative to less frequent words (which we component letters or words. In this case, the subject ter have called the "word-frequency disadvantage'u.' minates the processing of the lower-level units in that Although there are many procedural differences be segment of text and moves on to process the next seg tween the studies showing facilitating effects of famil ment, reading unit. If this subject were engaged in a letter iarity and our studies showing disruptive effects, one detection task with t as target, an error would be made factor seems to be crucial-namely, the number of words in this case because the letter t would not be identified. in view at any given time. In the studies demonstrating Thus, according to these hypotheses, letter-detection er the word-superiority effect and the word-frequency ad rors should occur whenever a larger unit (such as afthe) vantage, the usual procedures include tachistoscopic is identified prior to the identification of a target letter presentation followed by masking ofa single word or let contained in that unit (such as t). Because familiarity ter string at a time (but see, e.g., Krueger, 1970, 1982, with a unit is likely to aid its processing, letter-detection and Krueger & Weiss, 1976, for word-superiority effects errors should occur most often when the higher-level with multi-item displays). The subject is typically re units are familiar. In this way, the unitization hypothe quired to make a response to each letter string, by de ses can account for the disruptive effects of familiarity ciding, for example, which one oftwo alternative letters on letter detection.' LETTER DETECTION: A WINDOW TO UNITIZATION 337

Healy (in press) investigated changes in familiarity due to training and demonstrated a substantial decline in the magnitude of the word-frequency disadvantage with Supra------.... /--~ practice. It was also shown that this decline was highly word lof the I Ireading unit I specific to the particular target letters and test words level used during training but could not be attributed simply /-\~-~ to a change in the subjects' conscious detection strategy, Word such as a realization on the part ofthe subjects that a par level I readingl lunit I ticular word (like the) always contains a target letter. For example, in one study (Proctor, Healy, & Fendrich, [~ ,-~ L-~ 1988) subjects were given instructions explicitly telling Syllable them that the word the contains the target and that they read §:g] lun itl level should be careful not to forget to mark it. These in structions did lead to an increase in the number of tar ,-, gets detected in the word the, thus reducing the magni Letter ~ ,\< ,- J--, level ~ 0~ OJ ~~mm tude of the word-frequency disadvantage, but a substantial effect remained. How can the unitization hypotheses accommodate the i \ r I \1r! facilitating effects of word context on letter identifica Feature ( f I r 0 "C(lOI~J ... r I + level tion found in tachistoscopic masking procedures? It is assumed that subjects move on to the next word in the text once they have identified a given word. However, if Actua I of the reading un i there is no subsequent word to which the subjects can di Input rect their attention, as when only one word is in view, the subjects would naturally continue to process the single Figure 1.The operation ofthe unitization hypotheses for the read word in view once it has been identified. Under those ing of a short segment of text by a hypothetical subject. circumstances, processing at the letter level may be fa cilitated rather than disrupted by word identification be cause ofinferences based on the word's identity, such as Evidence for the assumptions embodied in Figure 1 the inference that a t must be present because the word comes from several sources. For instance, the need for the was identified. Thus, the unitization account can ex four levels ofreading units beyond the feature level (i.e., plain both the disruptive effects of familiarity with the the letter level, the syllable level, the word level, and the letter-detection paradigm and the facilitating effects of supraword level) has been empirically documented. Data familiarity with tachistoscopic masking procedures. It from Healy (1981b), Healy, Volbrecht, and Nye (1983), does so by assuming that the faster processing offamil and Schneider and Healy (1993) provide evidence con iar words leads subjects to spend less time processing cerning the nature and processing of the letter level; component letters in the letter-detection paradigm but these studies showed, for example, that subjects tolerate affords them more time to process component letters in missing letter features but do not tolerate additional fea the tachistoscopic masking procedures. tures. Drewnowski and Healy (1980) reported data rel Effects of display size. These hypotheses lead to the evant to the syllable level; this study showed that the suf prediction that a familiar word context will disrupt let fix morpheme -ing serves as a single unit in reading. ter detection when several words are simultaneously in Healy and Cunningham (1992) and Schneider and Healy view but will enhance letter detection when only one (1993) investigated unitization at the word level; for ex word is in view at a time. Healy, Oliver, and McNamara ample, it was shown that word shape is an important (1987) tested this prediction by employing a new letter variable in recognizing familiar words. Finally, Drew detection task in which the number ofwords in view was nowski and Healy (1977), Healy, Conboy, and Drewnow systematically manipulated. This procedure, which is a ski (1987), and Healy and Drewnowski (1983) reported variant of the rapid serial visual presentation technique evidence concerning the supraword level; in these stud developed by Forster (1970), involves the presentation ies it was shown, for example, that the reading unit for of continuous text on a computer display screen. Each the includes the preceding interword space. display is shown for a fixed amount oftime at the same The claim that the particular units identified depend location, and the subjects are to press a response key on their familiarity for the subject is supported by stud whenever they detect the target. In reviewing this 1987 ies investigating changes in familiarity due to develop study here, I will describe only Experiment 1, in which ment in children (Cunningham, Healy,Kanengiser, Chiz we examined the effect ofword frequency by comparing zick, & Willitts, 1988; Drewnowski, 1978, 1981). These the, the most frequent word in English, with other, less studies provided evidence for the use of increasingly frequent words and assessed the existence of word larger units as the subjects' reading ability increases. superiority or word-inferiority effects by comparing Healy, Fendrich, and Proctor (1990) and Proctor and correctly spelled words with words that were misspelled 338 HEALY

by replacing one of the correct letters with another let Hadley and Healy (1991) suggested that with only one ter. The text read by subjects was a prose passage, a short word in view, subjects would be forced to fixate every segment ofwhich is included in Table 2. The following word in a passage. Ordinarily-that is, with normal text three conditions were compared: (I) the "paper" condi and several words in view-familiar words may be iden tion, in which subjects read the text and circled each in tified in the parafovea(i.e., while fixating a previousword) stance of the letter t, as in the standard letter-detection and thus left unfixated. An eye-movement monitoring task; (2) the "four-word" condition, in which the text experiment by O'Regan (1979), for example, showed was presented on a computer display screen four words that the word the is often identified in the parafovea and at a time for a fixed duration and the subjects pressed a is thus not fixated while reading. Consequently, Hadley response key whenever they detected the target letter and Healy speculated that the perceptual unit that (the passage was written so that there was a maximum predominates in reading may depend on where identifi of one target in every four-worddisplay); and (3) the "one cation takes place in the visual field. This parafoveal word" condition, which was just like the four-word con processing hypothesis explains the large number of letter dition except that only one word was displayed at a time. detection errors on common words as resulting from the The results are summarized in Table 4 in terms of fact that words that are identified in the parafovea are mean error proportions as a function of condition, test not fixated during reading, so that letter identification is word type, and test-word spelling. As in the earlier stud impeded. That is, the familiar visual configuration of a ies, subjects in the paper condition made more errors on common word may allow for it to be identified in the correctly spelled words than they did on misspelled parafovea before its component letters are identified, pre words, and they made more errors on the very common sumably because greater acuity and resolution are needed word the than they did on other, less frequent words. for the identification of individual letters than for the More importantly, there was a large interaction between identification of a global word shape. If the same word test-word type and test-word spelling, reflecting the fact is fixated, it is much less likely that it would be identi that the difference between the and other words was fied as a whole before its individual letters are identified. greatly reduced when the words were misspelled. The Hadley and Healy (1991) reported four experiments pattern of errors for the four-word condition was simi which provided support for this hypothesis; I will de lar to that in the paper condition, although somewhat scribe only Experiment 4 here. In this experiment, we less striking. But the pattern of errors in the one-word provided the subjects with a small aperture cut into an condition was very different: There was no difference in index card and used as a viewing window. The subjects this case between correctly spelled words and mis moved this window across the page as they read the text. spelled words, and subjects made significantly fewer er The window was large enough for either only 5 letters rors on the than they did on other, less frequent words.' (e.g., the word the and the two surrounding spaces) or These results reflect a strong word-inferiority effect and only 15 letters (e.g., the word the along with the imme a strong word-frequency disadvantage for the four-word diately surrounding spaces and adjacent words or letters) and paper conditions, in contrast to the absence or re to be viewed, as illustrated in Table 2. The subjects in versal ofthese effects for the one-word condition. These both window-size conditions were given the same text to findings are consistent with the unitization hypotheses, read, and the text, which was a normal prose passage which imply that the number ofwords in view at a given identical to that used earlier (Healy, 1976; see also time is crucial because subjects can only move on to the Table 1), was printed normally. Unlike the procedure by next word in the text-leading to disruptive effects of Healy, Oliver, and McNamara (1987), in which the du word familiarity-if more than one word is in view.6 ration ofthe one-word and four-word displays was con stant and fixed by the computer, in this experiment the Visual Factors subjects controlled the movement ofthe window. Since Healy, Oliver, and McNamara (1987) explained the under the latter conditions there is no reason why sub findings for the one-word condition by suggesting that jects would spend extra processing time at the letter level with only one word in view subjects may be led, after word after word identification is completed in the smaller identification is completed, to engage in extra process window condition, this experiment allows for a direct ing at the letter level. Alternatively,in a more recent study, test ofthe parafoveal-processing hypothesis because the manipulation of window size directly manipulates the Table 4 availability of a parafoveal preview. No parafoveal pre Proportion of Detection Errors in Experiment 1 ofthe Study by view would be possible with the 5-letter window, but a Healy, Oliver, and McNamara (1987) as a Function of Condition, preview would be possible with the 15-letter window. Test-Word Type, and Test-Word Spelling (Correct or MisspeUed) The parafoveal-processing hypothesis leads to the predic Test-Word Type tion that only the 15-letter window would display a The Other Words larger proportion of letter-detection errors on the word Condition Correct Misspelled Correct Misspelled the than on other words. Indeed, as predicted, the pro One word .02 .01 .03 .04 portion of detection errors differed across test words Four word .16 .00 .06 .03 only for the 15-letter window (the, .15; other, .06). For Paper .55 .13 .30 .10 the 5-letter window, the difference was not significant LETTER DETECTION: A WINDOW TO UNITIZATION 339

the, .12; other, .10). Thus, eliminating the availability of another explanation for the large number ofletter-detection l parafoveal preview, as in the 5-letter window, elimi errors on the common word of Goldman and Healy fa rated the difference between letter-detection errors on the vored this unitization explanation. vord the and on other words. It therefore seems clear that Schneider, Healy, and Gesi (1991) aimed to test these he location of a word in the subject's visual field is a two alternative explanations-that is, Read's (1983) pro :rucial determinant of the pattern ofletter-detection er posal concerning the scanning of phonologically re ors on the word. When a familiar word occurs in the coded text and the unitization hypotheses favored by iarafovea, it may be identified before its component let Goldman and Healy (1985). The goal of Experiment 1 ers are identified, and therefore letter-detection errors of the study by Schneider et al. was to test the unitiza nay result, whereas when the same word is fixated, it is tion explanation using a previous finding by Healy, nuch less likely that word identification will precede Conboy, and Drewnowski (1987) that the tendency of etter identification, resulting in little chance ofa letter subjects to make errors on a common word was greatly ietection error. Although my original study (Healy, diminished when asterisks were inserted between all let 1976) ruled out the location ofthe letter in a word as an ters. The asterisks should impede the formation of pro mportant cause of letter-detection errors on the word cessing units larger than the letter by disrupting the fa 'he, this more recent study demonstrated that a revised miliar visual configuration ofthe units. In Experiment I version of the location hypothesis in terms of word 10 by Schneider et aI., asterisks were introduced into a pas cation in the visual field has much merit. Likewise, al sage for one group of subjects, whereas a second group hough my original study ruled out the pronunciation of of subjects were shown the same passage printed nor :he letter t as a sufficient explanation for letter-detection mally. Both versions of the passage are illustrated in errors on the word the, my colleagues and I have found Table 2. Subjects in both groups were given the letter nore recently that phonetic processes do affect letter de detection task withf as the target. In the normal condi tection in some cases. tion' we found a large proportion ofdetection errors for of(.56) relative to that for the other test words (.03); the Phonetic Factors effect of test word was greatly diminished in the aster One persistent question in the study of reading con isk condition (of, .17; other, .02), although it did remain cerns the role ofphonetic processes in word identifica substantial there. tion. A widely cited source of evidence on this issue is These results imply that unitization can provide at the classic study, mentioned earlier, by Corcoran (1966), least a partial explanation ofthe large proportion ofde who found that, in searching for the letter e in a maga tection errors on the word of However, the unitization zine article, subjects missed more silent es than pro explanation seems inconsistent with Read's (1983) ob nounced es (for similar observations, see Chen, 1976; servation of no difference between ofand other words Coltheart, Hull, & Slater, 1975; Locke, 1978; and Mohan, when the target was the letter a rather thanf But the only 1978; but for problems with these observations or bounds passage Read used with the a target was the same single on their generality, also see Drewnowski & Healy, 1982; sentence we employed, which contains only four as, Krueger, 1992; and Smith & Groat, 1979). Corcoran ar three of them in the word of(see Table 2). The purpose gued that when looking for the target, subjects scanned of Experiment 2 by Schneider et al. (1991) was to de a phonologically recoded version ofthe text, not just the termine whether subjects would miss a greater propor visual representation, and missed silent es because they tion ofas in the word ofwith a longer passage that has were not evident in the phonological version. more instances ofthe target letter. One group ofsubjects Subsequently, Read (1983) found that more letter was given a and another was given f as the target. The detection errors were made on the fin the word ofthan passage was written so that every test word contained were made onfs in other words. He attributed this effect both targets and there were no other instances of either to the unusual pronunciation of the letterf in the word target in the passage. We found a much greater propor of Like Corcoran (1966), Read argued that subjects tion of errors on of (.52) than on the other test words miss the fs in afbecause they scan a phonologically re (.05) for the ftarget condition; this effect of test word coded version of the passage and look for the phoneme was much smaller, but still statistically reliable, for the IfI. This argument seems reasonable because the letterf a-target condition (af, .10; other words, .02). These find usually corresponds to the phoneme IfI, with ofbeing the ings imply that unitization can account for the greater only exception among common words. However, Gold proportion ofdetection errors on afthan on other words, man and Healy (1985) found a large proportion ofletter but only partially. Other factors must also be contribut detection errors onfs in the word ofeven when subjects ing to the large effect with the target letterf were engaged in articulatory suppression (i.e., they spoke To determine whether phonetic factors contribute to an irrelevant word) during the detection task (normal: of, the failure ofsubjects to detectfs in the word of, Schnei .93; other, .03; suppression: of, .94; other, .10). Articu der et aI. (1991) used a procedure developed earlier by latory suppression has been shown to disrupt phonolog Schneider, Healy, Ericsson, and Bourne (1989). This ical recoding in previous studies of reading (e.g., Levy, procedure involves a comparison of two new detection 1978). Hence, this finding provides evidence against tasks. In the auditory task, subjects listen to a passage Read's argument. The unitization hypotheses provide and write down every word they hear that includes a 340 HEALY

given target letter. (Note that despite the auditory pre results provide evidence against Read's phonological sentation of the material, the subjects' task is to search recoding hypothesis. It seems unlikely that subjects for an orthographic, not a phonemic, target.) In the cor given the targets f or v would miss the f in ofbecause responding visual task, subjects read the passage and they are searching only for the phoneme IfI. Hence, write down every word they see that includes the target. some other phonetic processes must be responsible for In the earlier study, Schneider et al. (1989) found that of the failure of subjects to detect the f in of the two tasks, only the visual task yielded evidence for The findings ofExperiment 3 (Schneider et aI., 1991) unitization-that is, more letter-detection errors on com that support the hypothesis that phonetic processes con mon words than on less frequent words. Ifthe detection tribute to the failure ofsubjects to detectfs in ofmay ap errors onfin ofare due to its unusual pronunciation, as pear inconsistent with those ofExperiment 4 that provide argued by Read (1983), the f in ofshould be missed in evidence against the phonological-recoding hypothesis the auditory task as well as in the visual task. If, on the put forth by Read (1983). This inconsistency can be re other hand, the detection errors onfin ofare due to uni moved, however, by acknowledging that there are two tization, the f in ofshould be no more likely than the fs different types ofphonetic processes that have been pro in other words to be missed in the auditory task. posed previously (e.g., Besner & Davelaar, 1982; Foss Schneider et al. (1991) used the detection-task com & Blank, 1980). One type is used for accessing the lex parison with the targets f and 0 in Experiment 3. With icon, while the second type is used for short-term mem both modalities, for the targetfthere was a larger pro ory storage. Besner and Davelaar (1982) showed that only portion oferrors on of(visual, .57; auditory, .45) than on the memory processes are affected by articulatory sup the control word if (visual, .10; auditory, .19), even pression. Because articulatory suppression did not elim though ifis also a common word and is matched with of inate the large proportion ofdetection errors onfs in of in terms of word length and location ofthe target letter; in the study by Goldman and Healy (1985), this effect is the proportion of errors on ofwas larger, too, than that probably not attributable to memory processes. Instead, on other words withf(visual, .10; auditory, .22). This it is possible that lexical phonetic processes are respon finding is consistent with the hypothesis that the large sible. If we assume that speech perception and reading proportion oferrors onfin ofis due in part to its unusual share the relevant lexical phonetic processes, we have pronunciation. For the target 0, with the visual but not support for this possibility from our finding that a large with the auditory modality, the proportion of errors on proportion ofdetection errors occurs onfin ofwith the of (visual, .16; auditory, .20) was higher than that on auditory modality as well as with the visual modality. other test words (visual, .02; auditory, .20), suggesting How could lexical phonetic processes account for de that unitization is largely responsible for that effect. The tection errors onfin of? As an explanation for the large difference between the two modalities suggests that pro proportion ofdetection errors onfin of, Schneider et al. nunciation ofthe target letter was the factor responsible (1991) proposed that detection error rate is increased for the effect of test word found with the target f in the whenever there is a mismatch between the phoneme and auditory modality as well as in the visual modality. letter representations ofthe target in a word. That is, sub According to Read (1983), pronunciation ofthe target jects miss the f in of because there is a mismatch be affects detection errors because subjects scan a phono tween the letter f and the phoneme Ivl in the lexical logically recoded version ofthe text for the IfI phoneme entry. This explanation implies that a model of word and they miss thefin ofbecause it is pronounced like a identification needs to include both letter and phoneme Ivl rather than an IfI. The aim ofExperiment 4 by Schnei levels as well as a cross-checking or communication be der et al. (1991) was to test this explanation more di tween the two levels (see LaBerge & Samuels, 1974, for rectly. Three different conditions were compared, in one a similar proposal)." ofwhich subjects were given the single target letterf, as In subsequent experiments, Schneider et al. (1991) in earlier experiments. In a second condition, subjects and Schneider and Healy (1993) provided additional were given the pair of target letters f and v. If subjects support for this explanation. For example, in one exper make detection errors on the f in ofbecause it is pro iment, Schneider and Healy (1993) used the auditory de nounced like a v, they should be able to detect the f in tection task with phonemes rather than letters as targets, this condition even ifthey search for phonemes instead not unlike studies of phoneme monitoring (see, e.g., ofletters. In the third condition, subjects were given the Cutler, Mehler, Norris, & Segui, 1987; Healy & Cutting, pair oftarget lettersfand z. There were no zs or vs in the 1976). Two conditions were compared, in one of which test passage. This condition thus allows for a compari subjects searched for the phoneme lvi, while in the other son of the effects of having two targets with the effects they searched for the schwa phoneme luh/. The passages ofhaving a single one. We found that in all three condi used were constructed so that each test word in them in tions the proportion ofdetection errors was much higher cluded both target phonemes (e.g., of, love) and they in for the test word of(ftarget, .78;for v target, .64;for z cluded no other instances ofeither target phoneme. Ac target, .70) than it was for the other test words (ftarget, cording to our cross-checking hypothesis, subjects .06;for v target, .07;for z target, .09). Because subjects should make a larger proportion of errors on ofthan on continued to missfs in the word ofeven when they were other test words when searching for the Ivl phoneme, but told to search for the letter v as well as the letter f, these not when searching for the luhl phoneme, because there LETTER DETECTION: A WINDOW TO UNITIZATION 341 is a mismatch between the phoneme and letter represen string, that is the critical factor for letter detection in tations ofthe target for the Ivl target but not for the luhl some cases. target. In agreement with these predictions, we found Similarly, in describing their study of letter detection that there were significantly more detection errors on of in nonwords (Koriat & Greenberg, 1991), Koriat and than on other test words for the Ivl phoneme (of, .29; Greenberg (1994) conclude that "the missing-letter ef other words, .03) but not for the luhl phoneme (of, .21; fect can be obtained even for letter strings with zero fre other words, .14). quency of occurrence in the language" (p. 351), again suggesting that they have provided evidence against the Semantic and Syntactic Factors unitization framework, in which the frequency of a unit Now that I have described some recent studies show in the language is of paramount importance. However, ing the importance of visual and phonetic factors in they showedthat the nonwords demonstrating the missing letter- and word-identification processes in reading, I letter effect either included a morpheme affix which shall turn to a discussion ofthe importance of syntactic could be viewed as the relevant unit rather than the en and semantic factors. Work published by Koriat, Green tire nonword or were misspellings of a very frequent berg, and Goldshmid (1991; see also Greenberg & Koriat, word (e.g.Jom forfor) which could be viewed as the rel 1991; Greenberg, Koriat, & Shapiro, 1992; Koriat & evant unit, as in the earlier study by Healy and Drew Greenberg, 1991, 1993, 1994) helped stimulate my in nowski (1983), which found the missing letter effect for terest in this question because they found evidence sup some misspellings ofthe word the. porting the influence of syntactic factors on letter de It is also important to note that although the structural tection in Hebrew and English (see Haber & Schindler, account of Koriat and Greenberg (1994) provides a 1981, and Schindler, 1978, for earlier evidence also sug compelling explanation for the syntactic effects on let gesting the influence of syntactic function). ter detection, it cannot by itselfaccount for many of the Workby Koriat and Greenberg. On the basis oftheir other effects obtained with the letter-detection task. For finding of syntactic effects on letter detection, Koriat example, it cannot account for observed differences be and Greenberg (1994) have proposed a structural ac tween common and rare nouns (i.e., content words; see count of letter detection, according to which function Healy, 1976, 1980) or for many effects involving per words play an early role in sentence processing but then ceptual aspects ofwords, such as the typecase or font in recede to the background, so that their component let which they are printed or the spacing between letters ters may be missed in a letter-detection task. By this ac (see, e.g., Drewnowski & Healy, 1977; Healy, Conboy, count, letter detection thus reflects processes occurring & Drewnowski, 1987; Schneider & Healy, 1993). Like after word identification is completed, rather than re wise, the structural account has no explanation for pho flecting unitization processes occurring during lexical netic effects in letter detection, such as those concern access. However, it appears that the unitization frame ing syllable stress (see, e.g., Drewnowski & Healy, 1982; work can provide alternative accounts for most if not all Goldman & Healy, 1985) or the pronunciation of the tar ofthe findings summarized by Koriat and Greenberg. get letter (see, e.g., Read, 1983; Schneider et al., 1991). For example, Koriat et al. (1991) conducted an ex Work by Moravcsik and Healy. In further pursuit of periment in which they compared two kinds ofHebrew this issue, Moravcsik and Healy (in press) conducted a phrases: a preposition followed by a noun, and a con set of experiments that also demonstrate dramatic effects traction in which the first letter of the preposition was of semantic and syntactic factors on letter detection. I attached to the noun as a prefix. They found more letter will summarize the first two ofthese experiments here. detection errors for the prefix than for the preposition. In Experiment 1, we looked at semantic and syntactic That is, subjects made many letter-detection errors on factors by changing the meaning and grammatical func the first letter of the contraction, even though the com tion ofthe word the in a prose passage. The passage con bination of first letter and noun was uncommon. In de sisted of a story about a young man who was trying to scribing this study later, Koriat and Greenberg (1994) find two spices to use in a Thai recipe. The word the was concluded that "function units are concealed because of used in some cases in the passage to refer to a type of their syntactic role-not because of their familiarity" Thai spice. In an alternative version ofthe passage, the (p. 349), thereby suggesting that they provided evidence word thy was used in place of the to refer to the spice. A for the structural account and against the unitization sample sentence from each version ofthe passage is in framework. However, that evidence was based on the as cluded in Table 2. Note that the name of the spice was sumption that "the frequency ofthe orthographic string not in quotes or made to stand out in any other way. Each is the critical factor for letter omissions" (p. 349), which version ofthe passage was shown to halfofthe subjects. is not an assumption included in the unitization frame We found that the proportion of detection errors on work. To the contrary, Drewnowski and Healy (1980) the word the was very high when it was used in the or made it clear in their study ofdetection errors in the tri dinary way (.38), but that it decreased dramatically when gram -ing, which provided support for the unitization the meaning and grammatical function were changed. framework, that it may be the frequency of the mor The proportion ofletter-detection errors on the word the pheme affix, rather than that of the entire orthographic when it referred to a spice was essentially on the floor 342 HEALY

(.02), was no different from that on the word thy when it different presents were mentioned, followed by a refer was used in the same way (.0 I), and was actually less ence to "the present." Syntactic factors on their own than the proportion of errors on other test words (.13). were also shown to be important in a more recent study These results show that semantic and syntactic factors by Moravcsik and Healy (1994), in which it was found are indeed of crucial importance, contrary to the sug that subjects made more correct letter detections on the gestion from my initial study (Healy, 1976), which word the when it belonged to the subject than they did showed that scrambling the words in a passage did not when it belonged to the object ofa sentence, even when affect the relative proportion ofletter-detection errors on the semantic role of the noun phrase was controlled by the word the. The present findings are noteworthy be using active and passive versions ofthe same sentences. cause they suggest that grammar and meaning play im It thus appears that semantic and syntactic factors both portant roles very early on in letter and word processing, jointly and independently affect letter detection. before letter detection is completed. To extend the findings from the first experiment in Conclusions this series, Moravcsik and Healy (in press) conducted a In my original work with the letter-detection task second experiment using a different meaning of the (Healy, 1976), I found evidence supporting the important word the. Instead ofconstructing a new use for the word role ofunitization processes and evidence against the role the, in this experiment, one ofits existing, but relatively of letter location, letter pronunciation, and the semantic unusual, uses was employed. Specifically, the word the and syntactic redundancy of the words. In contrast, in my referred to itself-that is, to the definite article. We em more recent work, without denigrating the importance of ployed two different versions ofan excerpt from a gram unitization, my collaborators and I have found that word mar textbook about the definite article. This excerpt in location in the parafovea (Hadley & Healy, 1991), the cluded the phrase "the definite article" several times. phonetic representation of the letter (Schneider & Healy, One version ofthe passage was identical to the excerpt, 1993; Schneider et aI., 1991), and the semantic and syn and the other version was the same except that every in tactic function ofthe word in the text (Moravcsik & Healy, stance of the phrase "the definite article" was replaced 1994, in press) also play crucial roles in letter detection. by the word the. One sentence from each version ofthe Can we incorporate these additional factors into the passage is included in Table 2. It should be noted that the framework provided by the unitization hypotheses? The word the in the phrase "the definite article" is in the answer to this question is clearly positive, as should be same place in the sentence and that the same words im clear by reconsidering Figure I, which shows the opera mediately precede it as precede the word the when it is tion ofthese hypotheses for the reading of a short segment used on its own to mean the definite article. Also note of text by a hypothetical subject. The additional factors that the word the was not placed in quotes or made to can be incorporated by making the following three new stand out in any way even when it referred to itself. Each assumptions: (1) identification at the word level is much version ofthe passage was shown to halfofthe subjects. less likely to precede identification at the letter levelwhen As expected, we found that the proportion of detec the word is fixated rather than occurring in the parafovea; tion errors was high for the word the when it occurred (2) along with the letter level, there must be a phoneme either in the phrase "the definite article" (.37) or else level as well as a provision for a cross-checking or com where in the passage as a function word (.39), but that munication between those two levels; and (3) word iden the proportion oferrors was much lower for the word the tification must require access to semantic and syntactic when it occurred as a content word referring to the def information, not just information about the visual con inite article (.15). In fact, the proportion oferrors on the figuration and component letters, phonemes, and sylla word the when used in this special way was no greater bles. This last assumption would, for example, allow for than the proportion of errors on other test words (.18). words with a common meaning and grammatical function Again, these results give strong support to the hypothe to be identified before words with unusual semantic and sis that semantic and syntactic factors influence the pat syntactic attributes. tern of letter-detection errors. In summary, the simple task of circling letters in a In the two experiments described here by Moravcsik word depends not only on the familiarity of the word's and Healy (in press), semantic and syntactic factors were configuration but also on the location of the word in the confounded; that is, both the meaning and grammatical reader's visual field, the phonetic representation of the function ofthe word the were changed. 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O·REGAN. K. (1979). Saccade size control in reading: Evidence for the contributing to the macrolevel speed-accuracy trade-off. However, a linguistic control hypothesis. Perception & Psychophysics. 25. 501 microlevel speed-accuracy trade-off is the basis for a processing-time 509. hypothesis proposed recently by Moravcsik and Healy (in press), ac PETERZELL. D. H.. SINCLAIR. G. P. HEALY. A. E. & BOURNE. L. E.. JR. cording to which the length of time spent processing a given word is (1990). Identification of letters in the predesignated target para a major determinant of the proportion of letter-detection errors made digm: A word superiority effect for the common word the. Ameri on that word. can Journal ofPsvchologv; 103.299-315. 2. Most previous studies of the word-superiority effect and word PROCTOR. J. D.. & HEALY. A. E ( 1985). A secondary-task analysis of frequency advantage with the masking paradigm avoided common a word familiarity effect. Journal of' Experimental Psychology: function words. However.in a study with the masking paradigm by Peter Human Perception & Performance. 11.286-303. zell, Sinclair, Healy, and Bourne (1990), a word-superiority effect was PROCTOR. 1. D.. & HEALY. A. E (in press). Acquisition and retention found for the common function word the even under circumstances in of skilled letter detection. In A. F. Healy & L. E. Bourne. Jr. (Eds.), which the effect was not found for less common words. Learning and memory of' kno....ledge and skills: Durability and 3. Note that research with the Stroop (1935) task also shows poorer specificity (pp. 282-299). Thousand Oaks. CA: Sage. performance (i.e., greater interference) with words than with nonwords PROCTOR. J. D.• & HEALY. A. E, & FENDRICH. D. W. (1988, March). and with common words than with rare words (see. e.g., Klein, 1964; The disappearance ofthe ....ord inferiority effect: Strategy shift or Macleod,1991). perceptual effect? Paper presented at the annual meeting of the 4. For comparisons of these unitization hypotheses with related Southeastern Psychological Association, New Orleans. LA. models emphasizing holistic processing and for tests of unitization RAYNER. K.. & POLLATSEK. A. (1989). The psychology ofreading, En using paradigms other than the letter-detection task-some of which glewood Cliffs. NJ: Prentice-Hall. showed word superiority rather than word inferiority-see. for exam READ, J. D. (1983). Detection of Fs in a single statement: The role of ple, Allen and Emerson (1991), Allen and Madden (1990). Johnson, phonetic recoding. Memory & Cognition. 11,390-399. Allen, and Strand (1989). and Krueger (1989). REICHER, G. M. (1969). Perceptual recognition as a function ofmean 5. The same general pattern of results was evident for correct rc ingfulness of stimulus material. Journal ojExperimental Psychol sponse latencies as was evident for errors, which speaks against po ogy, 81. 275-280. tential problems not only concerning speed-accuracy trade-offs (see RUMELHART, D. E., & MCCLELLAND. J. L. (1982). An interactive Note I) but also concerning floor effects on error rate. It is particu activation model of context effects in letter perception: Part 2. The larly interesting to note that whereas response latencies in the one contextual enhancement effect and some tests and extensions ofthe word condition were fastest on the word the when it was spelled cor model. Psychological Review, 89, 60-94. rectly. response latencies in the four-word condition were slowest in SCHINDLER, R. M. (1978). The effect ofprose context on visual search that situation (see Healy, Oliver. & McNamara. 1987, pp, 282-283). for letters. Memory & Cognition. 6, 124-130. 6. As mentioned earlier, work by Krueger and his colleagues SCHNEIDER, y. 1., & HEALY, A. E (1993). Detecting phonemes and let (Krueger, 1970, 1982; Krueger & Weiss, 1976) obtained word su ters in text: Interactions between different types and levels of periority, not inferiority, with multi-item displays. However, there processes. Memory & Cognition, 21. 739-751. are many differences between the procedures used by Krueger and SCHNEIDER. Y. L, HEALY. A. E, ERICSSON. K. A.. & BOURNE, L. E.. JR. his colleagues and those used in the letter-detection task (see Healy, (1989). letter detection errors in reading. auditory, and memory 1976, 1980 for discussions of some procedural differences). tasks. Journal ojMemory & Language, 28, 400-411. Krueger and his colleagues used a search task in which subjects SCHNEIDER. Y. 1., HEALY, A. E, & GESI. A. T. (1991). The role of pho looked for target letters in lists containing either words or nonwords, netic processes in letter detection: A reevaluation. Journal ofMem responding "yes" whenever they found a target and "no" if no tar ory & Language. 30, 294-318. get was found in a list. One critical difference between Krueger's SMITH. P.T., & GROAT, A. (1979). Spelling patterns, letter cancellation procedures and those used in the letter-detection task concerns the and the processing oftext. In P. A. Kolers, M. E. Wrolstad, & H. Bouma fact that detection was stressed in Krueger's search task whereas (Eds.), Processing of visible language (Vol. I, pp. 309-324). New reading, rather than detection, was stressed in the letter-detection York: Plenum. task (see Healy, 1976 for a discussion of this difference). Further, STROOP, J. R. (1935). Studies ofinterference in serial verbal reactions. the words in the letter-detection task are typically presented in a Journal ojExperimental Psychology, 18,643-662. paragraph format, whereas those in Krueger's search task were typ WHEELER. D. D. (1970). Processes in word recognition. Cognitive Psy ically presented in a list format. In fact, Drewnowski and Healy chology. 1,59-85. (1977) found that the word-frequency disadvantage was eliminated in the letter-detection task when the words were presented in a list, NOTES rather than a paragraph, format. 7. Note that the cross-checking postulated by Schneider et al. (1991) 1. It is important to distinguish between the overall, or rnacrolevel, is also similar to a proposal by Krueger (1992) to account for his find speed-accuracy trade-offconsidered here for a passage as a whole and ing of an enhanced word-superiority effect for silent letters in words. a micro level speed-accuracy trade-off, which would apply to the in However, whereas Schneider et al. proposed that a mismatch between dividual words in a passage. Given a macro level speed-accuracy the phoneme and the letter representations ofthe target would disturb trade-off, subjects would make more letter-detection errors on pas performance on the letter-detection task, Krueger (1992) proposed that sages that they process more quickly. In contrast, given a microlevel such a mismatch would facilitate performance on his task in which sin speed-accuracy trade-off, subjects would make more letter-detection gle words rather than prose were presented, and in which a "yes" or errors on words that they process more quickly. Note that the proce "no" response was required to each word. dures used in Healy (1976) did not allow the determination ofthe de gree to which a microlevel speed-accuracy trade-off (which was nec (Manuscript received December 23, 1993; essarily embedded in the macrolevel speed-accuracy trade-oft) was revision accepted for publication May 8, 1994.)