In Helfrich, H. (Ed.), Time and mind (pp. 171-195). ;J Kirkland, WA: Hogrefe & Huber, 1996. :l Chapter 9: Models of psychological time revisited*
RICHARD A. BLOCK and DAN ZAKAY
Introduction Theorists have taken two seemingly different approaches to ex plaining, or modeling, psychological time (Block, 1990). These ap proaches have appeared under several guises. Ornstein (1969) referred to them as tlle sensory-process approach and the cognitive approach. Sensory-process models "postulate some sort of
Timing ,vith or \vithout a timer TIle important difference between tlle two approaches is not that the first concerns sensory processes and tllat the second concerns cognitive processes. Instead, the first class of model proposes timing witll a timer, whereas the second proposes timing WitilOllt a timer (Ivry & Hazeltine, 1992). In timing-with-a-timer models, a pacemaker mechanism lUlderlies
• We thank Hannes Eisler, Fran90ise Macar, John Moore, and Andras Semjen for helpful comments on an earlier draft of this chapter. , 1/_1 l72 Richard A. Block and Dan Zakay :1 Models of psychological lime revIsIted
.~'~l the psychological timing system. Two major variants are chronobiologi ~ more general. Consider, for example, Doob's (1971) model (Figure 1, p. 174). This model illustrates a taxonomy of time tllat depicts interactions cal and intemal-clock models (Block. 1990). J In timing-without-a-timer models, subjects construct psychological time from processed and stored 1:1' involving the "intricate. multivariate phenomenon of time" (p. 30). The information - that is, some salient aspect or byproduct of infonnation '~I details are relatively unimportant. For present purposes, we note tllat processing. Valiants of this kind of model include attentional, memory ~ altll0ugh tllis model may seem comprehensive, it is not a fW1ctional (e.g., :( infon1lation-processing) model of temporal behavior or judgment. storage, and memory change nlodels (Block, 1990). .~. ~ Pieron (1923) was one of the first researchers to discuss the possi ~ Block (1985) proposed a contextualistic model in which temporal ble relationship between body temperature and duration experience. i experience is a product of four kinds of interacting factors (Figure 2, p. 175). Again, tlle details are relatively unimportant, because model is Subsequently, Frant;ois (1927) and Hoagland (1933) obtained such evi ~r tllis dence. which SUppOlts a possible timing-with-a-timer model. Hoagland only a little more functionalistic than Doob's. 111e main advantage of f~ (1933; see also 1966) proposed that a masler chemical clock, or tempo R models such as Doob's (1971) and Block's (1985) is heuristic: tllese ral pacemaker, in the brain regulates time-related behaviors and judg ~ models remind us that psychological time involves complex interactions ments. TIle evidence suggested that the rate of repeated time productions , of various organismic and environmental variables. 111e main disadvan - involving counting at the rate of one per second - increases as a func , tage of these models, as noted ab~ve, is that they do not "relate in a fW1ctional way to the empirical findings [they are] supposed to repre tion of body temperature. More recent evidence suggests that duration ~ f sent" (Michon. 1985, p. 26). Although both models depict interactions judgments of many minutes (e.g., hourly productions) are correlated "~ with body temperature (Campbell & Bimbaum, 1994). Although the re of variables, several functional issues remain: (a) Which interactions are lationship between body temperature and shorter duration judgments is impOItant in particular situations and which are not? (b) What is tlle often inconsistent (Hancock, 1993), changes in body temperature do nature ofthe higher-order interactions? (c) How are the tmderlying proc seem to lead to systematic changes in the rate of psychological time esses sequenced, as in a functionalistically oriented infonnation-process (Wearden & Penton-Voak, 1995). One possibility is that body tempera ing model of temporal beha vior? I, ture influences general arousal level, which thereby influences the rate of i~ ;~ Cognitive psychologists and others have occasionally proposed a pacemaker mechanism (Wearden & Penton-Voak, 1995). The problem models resembling internal-clock models, but tllese usually involve tim with postulating that a pacemaker or master biochemical clock directly ing without a timer. For example, Lashley (1951) tllOught tllat practiced influences time-related behaviors and judgments is tllat temperature may movement sequence,s are structured as individual elements organized into also influence brain processes tllat subserve attentional, memory, and chunks which are executed as part of a motor program for tlle action se otller cognitive processes. Variations in tllese processes probably have quence. Because he proposed tllat a motor program is executed without little or no effect on body temperature. Because cognitive variables (e.g., the need for feedback, it needs an internal-control process to time ele attentional demands of a task) influence duration experience. cognitive ments. Researchers have searched for such a common mechanism tllat is processes may directly mediate temporal behaviors and judgments. Body able to stabilize motor programs despite changes in states of the organ temperature may indirectly influence temporal behaviors and judgmehts ism, changes in contextual stimuli, changes in equipment or instruments by altering whatever cognitive processes subserve psychological time used for the pClfonllance, and so on. 111e important question of how (Block, 1990). movement sequences are timed is still largely lmresolved, as is the ques Theorists have proposed a large number of cognitive models of tion of whether we need to propose an intemal-c1ock mechanism. Motor programs may contain internal, hierarchically organized infonnation psychological time. TIley have stated these mostly In tlle form of a "variable-x hypothesis:' where one may substitute any of several vari about timing relationships, so a pacemaker mechanism may be lumeces ables for variable-x (e.g., input segmentation, complexity-of-coding, at sary. Altemativeiy, even sllch information about timing relationships tentional selectivity). Each of these variables is typically tlle only one may rely on a pacemaker for some basic calibration (see Semjen, this that the researcher manipulated. A few models have attempted to be volume, chapter 2).
:~ An example of an internal-clock model is also desribcd in chapter 4 by H. 'If i Fi~l('r. ;i 174 Richard A. Bloch. ami Dan Zakay \ Models of psycho)ogicLd lillie revisited 175
.114 In the remainder of the chapter, we review various fonnal models of :~ psychological time. We propose the attentional-gate model, which recon :q ciles the two approaches. This model is somewhat isomorphic with ·iit ;il contextual-change models of experienced and remembered duration. ::.1 ~i IJ CHARACTERISTICS J OF EXPERIENCER .:\ '~ Species Sex Personality ] Interests 1 Previous experiences 1 1
CONTENTS OF ACTIVITIES DURING I TIME PERIOD(S) TIME PERIOD(S)
1 "Empty" 'Passive" nonattendlng "Filled' 'Passive" attending Active responding Active responding (linguistic (level of processing. pictorial. kind of encoding, I music etc.) strategies, Complexity etc.) TEMPORAL BEHAVIOR (METHODS) I i Judgments/Estimates of: simultaneity successiveness rhythm serial position order I 1 I spacing duration 1 Figure 2: Block's (1985) contextualistic model ot duration expenence.
Treislllan's Model Treisman (1963) proposed an influential model of an internal clock underlying human temporal judgment (Figure 3, p. 176). He postulated a pacemaker that produces a regular series of pulses, the rate of which varies as a ftmction of input from an organism'S specific arousal center. In his view, specific arousal is influenced by external events, in contrast to general arousal. which depends on internal mechanisms such as those tmderlying circadian rhythms. A counter records the number of pulses in a pathway, and the total is transferred into a store and into a comparator mechanism. A verbal selective mechanism assists in retrieving useful in fom1ation from the store. 111i5 is presumably a long-tenn memory store Figure I: Doob's (1971) taxonomy of time \7ti Richard A. Ulud. LlUJ Uau Lakay (.IUll;,:.!,; 01 p.})~I!I')I"i..>ILdi LllI ..... 1,_, containing knowledge of correspondences between total pulses and ver pulse rate. In our view, this minor modification docs not rectify the ballabels, sllch as 20 s, I Ill, and so on. limitations inherent in the model. Scalar-tinling Inodel Contemporary behavioral psychologists, who draw and test infer ences about timing processes in animals, have proposed internal-clock Specific models that resemble Treisman's (1963: 1993) model. TIlese researchers arousal center typically investigate time-related behavior of animals such as pigeons and rats during relatively short time periods (seconds to minutes). The ~ ~ ~ general finding is tllat animals are sensitive to different stimulus dura tions and time-based schedules of reinforcement. Pacemaker - Figure 4 (p. (77) shows the canonical model embodying tlle theory Pathway - , lUlderlying tllese explanations, called scalar timing IheOlY or scalar ex pectancy theOlJl. Because this model provides an excellent accOlUlt of a wide variety of evidence, many researchers have adopted it (e.g., Allan, Counter 1992; Church, 1984~ Gibbon & Church, 1984~ Gibbon et aI., 1984: ~I Roberts, 1983). The present account is ratller brief. We recommend ~ Comparator Church's (I989) excellent chapter for additional details, and also Lejeune & Richelle's chapter (tllis volume, chapter 8), which contains
Store I --t , 1 an especially valuable discussion of cross-species comparisons. 1 ~-I~ :1 'I Response• I mechanisms r ver~l:;e~ive mechanism -1 ::J i. J ~j
No (Wait) Figure 3: Treisman's (1963) model of the internal clock. Subsequently, several theorists proposed that the alpha rhythm may Ves reflect the frequency of the pacemaker component of the hypothetical (Rnpond) internal clock. Treisman (1984) attempted to detennine whether this is the case. However, his data do not SlippOlt the view tlIat arousal, afleast Figure 4: Scalar timing model (Church, 1984: Gibbon, as it is reflected in alpha frequency, influences the pacemaker rate. In a 1984). recent modification of this intcmal-clock model, Trcisman and his col This model accollnts for time (duration) perception and time pro leagues (Treisman et ai., 1990; Treisman, 1993) proposed a more com duction by proposing an intemal clock, memory stores, and a decision plex pacemaker, which includes a calibration unit that can modulate the mechanism. TIle intemal-clock consists of a pacemaker, a switch, and an accumulator. TIle pacemaker. operating like a metronome, automatically .~ 1'18 Richard A. Block and Dan Zakay Models of psycholog,ical time revisited 179 and autonomollsly generates more or less rrgulariy spaced pulses (at a propriate responding - that is, a temporally displaced response rate func rate of A pulses per second). When the organism perceives an external tion (Roberts & Church, 1978). ll1is implies that the internal clock signal indicating the beginning of a time peliod, the switch oper functions like a stopwatch, cumulatively timing the duration. The ates (perhaps with a slight lag, influenced by attention), thereby allowing startJstop button may be switched off for the duration of the offset of the pulses to pass through to an accumulator. The acculIlulator integrates timing signal. (This represents a slight elaboration on Treisman's model, and holds total pulse count during the time period (At). Perceived which did not propose a cOlmter-stopping mechanism.) duration is a monotonic function of the total number of pulses trans ferred into the accumulator. On any trial, the contents of the accumula Human evidence tor are transferred into a working lIleI1101)' store for comparison with the Because the scalar-timing model can time various periods, includ contents of the reference memOI)' store. The r~ference memory store ing internlpted fixed-interval schedules, it is able to handle virtually all contains a long-term memolY representation of the approximate number extant animal-timing data. However, the model does not take into ac of pulses that accumulated on past trials. This number is then trans COtult factors that are more prominent in humans than in other animals. ferred to the comparator with some bias, K *, a memory storage constant In particular, it is not easily able to explain why cognitive factors (e.g., that may be slightly less than or greater than 1. The comparator com ~ attention, strategies, infom1ation-processing tasks) influence temporal pares the contents (total pulse count) of the two stores. ~. ~ behaviors. This seems largely a consequence of methodological limita tions or neglect: few animal timing researchers have explored or dis Animal evidence cussed the effects of attentional manipulations, which have been a focus ll1e peak procedure, which uses a modified discrete-trials fixed-in of considerable research on human prospective duration timing. In addi ~ terval (FI) schedule, is a common method used to explore animal timing. ; tion, organisms may use repetitive or chained behaviors as "external ., clocks" to time intervals; that is, they may engage in movements for an A relatively long, variable interval separates each trial. TI1e onset of a .~ discriminative stimulus Stich as a light signals the start of each trial. On appropriate amount of time while they wait for reinforcement to be en most tlials, the first response occurring after a FI (e.g., 30 s) has elapsed abled (Pollthas, 1985). Thus, activities (such as strategies) of an organ since the start of the trial is remforced: then the discriminative stimulus ism during a time period influence its time-related behaviors. The scalar is turned off. On other trials, which are the most important ones for timing model does not incorporate this kind of "external" timing process. ~ , testing the theOly, the animal receives no reinforcement, and the dis ~ In short, internal-clock model:; proposed by behavioral psycholo criminative stimulus is tum::;d off only after a relatively long interval, t: ,i gists investigating timing in nonhuman animals seem somewhat limited usually at least tWice the F[ (e.g., 60 s). Averaged across many such (Block, 1990). Until these models consider the role of cognitive factors, 1 trials, the typical response rate is approximately a Gaussian (bell L j sllch as attentional allocation, they will not be able to generalize to ex shaped) function of time since the start of the interval. TIlis timing be ~ plaining human duration judgment. TI1ework of Richelle and Lejetule havior reveals a scalar propelty: regardless of Fllength, the average re f (see Lejeune & Richelle, this volume. chapter 8; Richelle & Lejeune, sponse rate at any time, expressed as a proportion of the peak rate·, is a 1980; Richelle et al., 1985) is a notable exception. They have conducted function of the proportion of the total duration that'has elapsed. In other comparative research involving several species, including humans, and words, the normalized response-rate curve does not vary much from one l' have included a role for cognitive factors. Richelle et al. (1985) thought F[ length to another. The intemal clock model handles this general find- i~ that the answer to the problem is to propose "as many clocks as there by proposing that the response rate increases in p!'obability as the are behaviors exhibiting timing properties" (p. 90). We take a different comparison of working memory and reference memory reveals a sil11ilar j. view. We propose a model containing a single "cognitive clock," a total Dulse count. ·i·r.~· h model with seemingly broad explanatory power (see "attentional-gate i~ model," later in this chapter). In the peak procedure and other similar procedures. the switch op "I~; erates at the onset of the discriminative stimulus, with some slight lag til 1~1 To justify sllch a model, we first consider the more cognitively ori attributable to attentional processes, and the accumulation of pulses be ;~ \.~ ented human research. We show that without additional elaboration the If an animal leams that the temporary offset of the timing signal ;}: will delav reinforcement bv the length of tlw offset ouratiotl, it shows ap 101 uw Richard A. Block anc..llJall Zakay )' Models of psychologlcallimt! revIsited f".(
Ii,I' scalar-timmg model cannot handle evidence on human timing and tem :;' same limited resourccs. However, Thomas's model is deficient in han poral judgmcnt. ~j dling the animal-timing data, as well as the role of physiological (non ~~, cognitive) factors. Because it assumes a constant pool of attentional re :n*l sources, it does not consider arousal level or variations in alertness at Thonlas's attentionH) rHodel j~: 4; tlibutable to circadian rhythms and other biological factors. It is also too Several theorists have .proposed models of psychological time in jl .' passive: 11lOmas proposed that stimulus infonllation alone detennines which attention to time, or temporal information processing, plays a i the allocation of attention and that strategies are not involved. TIle model major role. Thomas and his colleagues (11lO111as & Cantor, 1975; ~~ needs a concept of attention along the lines of Kahneman's (1973) re 11lomas & Weaver, 1975) developed and tested a mathematical model in source model. Kahneman argued that arousal detennines the total atten attentional allocation influences duration judgments. 11lis model tional resources available at any moment to meet infonnation-processing (Figure 5, p. 181) is the most explicitly fonnulated attentional model of demands. Thus, temporal information processing is influenced not only psychological tllne. It IS expressed as the ttUlctional equation: 1:(1) ex, by characteristics of the information-processing task, but also by mo f(t, I) + (l - ex,) g*(I). 11le model says that the perceived duration 1: of an mentalY arousal level and, hence, to::ll available resources. We need this interval containing certain information I is a monotonic flUlction of the modification of 11lOmas's model to handle new findings such as the fact weighted average of the amount of infomlation encoded by two proces that increased alertness, such as when a person is under the influence of sors, a temporal information processor f(t, I), and a nontemporal infor stimulants like methamphetamine, lengthens duration experience (Fran mation processor g*(I). 11le organism divides attention between the two kenhaeuser, 1959; Hicks, 1992). ~ processors. which flUlction ill parallel. Perceived duration is weighted 1; I' (with probability parameter ex) to optimize the reliability of the infonna- l·~ that each processor encodes, because as more attention is allocated 17 if Mostly to one processor, the other becomes more unreliable. As ex, approaches 1, Retrospective the subject encodes more temporal infonnatioll, and as ex approaches 0, \: Judgment the subject encodes more nontemporal infonnation. If less stimulus in ! i' fOmlation occurs during the to-be-judged duration, the organism allo \., I cates more attention to temporal information, and f(t, nis more heavily I, i: weighted. If a task demands more information processing, the organism ;1 allocates more attention to this nontemporal infonnation, and g*(I) is t: r more heavily weighted. I' ~' f' Although 11lOmas and his colleagues studied only human duration i·; 1J judgments of stimuli presented for less than 100 ms. one may consider ! the model to be a general model of temporal information processing, Mostly even involving longer time periods (Michon, 1985).. Prospective Judgment 11le strengths of this model complement the strengths of the scalar I timing model. Extant formulations and empirical tests of the scalar-tim ing model only use the concept of attention in a very limited way (see, 'I Figure 5: 11lOll1as's (11lomas & Cantor, 1975, 11lomas & :;j \Veaver, 1975) functional equation diagrammed as for example, Allan, 1992: Meek, 1984). Because attention plays a criti :1 i cal role in 11lOl11as's model, it handles an aspect of the human data 'j a model. scalar-timing models do not. 1t also makes slightly more precise tenlli :'t nology such as attention to time and temporal informatioll processing, :f which Block (1990) criticized as being overly vague. 111e model adds ,.r precision to these terms by implying that attending to time is like attend ing to stimulus information in that both processes require access to the 82 l<.lcflard A. Glock and Ual\ Zah.ay .~ ''t;' Models of psychologl<.:<.ll Lime H~Vlsitcu 183 ~. .~~ It Attcntional-gate model counter, rather than simply an accumulator, because controlled cogni We propose a model combining features of Treisman's (1963) ~. tive processes, sllch as attention, influence the input to it.) The rest of model, the scalar-timing model (Church, 1984: Gibbon & Church, 1984~ fl tlle model contains functional components analogous to tllose in tlle Gibbon ct 411., 1984), and Thomas's (Thomas & Cantor, 1975, 11lOmas ~ scalar-timing model. 11le momentary total pulse count in tlle cognitive if counter is transferred to a working memory store. (11lis process may oc & \\lcaver, 1975) model. We call this the allenlianal-gale model i~ cur only when attention is deployed, in contrast to the analogous process (Figure 6, p. 182). Consid6r first a version of the model that can handle ft. the kind of prospective duration timing which both Treisman's and sca f in tlle scalar-timing model, which is assumed to be automatic and con lar-timing models are designed to handle. The critical feature of prospec ! tinuous.) In addition, a reference memory store contains a record of the average total number of pulses that accumulated in the past before a tive timing is that the organism's behavior is focused on temporal in L ., certain time period was complete. (In humans, the reference memory formation, as a result of either leaming or instructions. ,/ '~ store may also contain learned correspondences between pulse totals and ~~ l~ verbal labels for temporal units.) If the momentary total pulse count in \.,'. I.:" working memory approximates the total in reference memory, a cogni To ::~ tive comparison (probably also involving attention) results in the organ Retrospective ~~ Model ism signaling tlle end of tlle time period or making some other duration dependent response. If fewer tllan the required number of total pulses have been counted, tlle orgamsm waits or makes a shorter duration judgment. At present, little or no evidence (whetller from animals or from hu mans) definitively tests some details of tllis model. For this reason, we are unsure about tlle relative location of two components, the attentional gate and the switch (Zakay & Block, 1994). It may be more appropriate to locate tlle switch before, instead of after, tlle attentional gate. Neitller logical analysis nor empirical evidence seems to favor one order over the otller. Differences in tlle dynamics of tllese two components suggests that tlley are separate components, instead of simply being a single at :' tentional switch (cf. Allan, 1992; Meck, 1984): The switch operates as 1'1 ;':,.1' a result of tlle organism's processing of external signals, whereas tlle gate operates as a result of tlle organism's internal allocation of atten tional resources. We are also lmsure about the appropriate metaphor to Yes (Ac:lpond) use for tlle flmctioning of tlle gate. Attention to time may be viewed as I opening the gate wider or more frequently, thereby allowing more pulses t:1 Figure 6: The attentional-gate model of prospective dura ':1 to pass through it to the cognitive counter. Neither logic nor evidence is tion timing. :~ available to distinguish these metaphors. " We propose that a pacemaker produces pulses at a rate which is in 11le attentional-gate model contains two important modifications to fluenccd by both general (e.g., circadian) and specific (e.g., stilllUlus 'I 'ii extant internal-cIock models. First, it incorporates the notion that a sub induccd) arollsal. E4Ich occ4lsion on which an organism attends to time, ,~ ject may divide attentional resources between attending to external I;, ~ as opposed to extemal stimulus cvcnts, opens a gale. This allows the events and attending to time (11lOl11as & Cantor, 1975; 11lomas & pulse strcam to be transmitted to subscfJucnt componcnts. At the onset of Y Weaver, 1975), and it specifies the consequences of each. Attending to :~ a duration, indicated by some start signal. the switch allows the pulse time is necessary for pulses to be transmitted to tlle cognitive cOlU1ter. stream to be transmitted to the cognitive counter, where pulses are While the duration is in progress (i.e" while tlle switch is allowing counted, or Slimmed over time. (\\le call this componcnt a cognitive pulses to pass to the cognitive counter), the number of transmitted pulses l84 Richard A. Block and Dan Zakay Models of psychological time revisited 185 is a fLUlction of two factors: (a) the pulse rate. which is influenced by assume such an effect. We propose another explanation: intensity of the general and specific arollsaL and (b) the proportion of time the gate is light influcnced the pigeons' allocation of attentional resources. open, or the width it is open, which is influenced by the amount of atten tion allocated to time. Contextual-change nlodel Few animal-timing experimeilts have presented varied stimulus in The processes underlying prospective duration judgment differ from fonnation during a time period. such during a FI or DRL (differential re those lUlderiying retrospective duration judgment (e.g., Block, 1992~ inforcement for low rate of responding) schedule (see, however, Macar, Hicks, Miller, & Kinsboume, 1976: Zakay, 1990; 1993). 1980). A start signal occurs at the beginning of a time period, but that is the only extemal information presented. An easy way to test the Prospective dunltion judgnlcnt attentional-gate model would be occasionally to present varied stimulus infonnation (novel events that have not been learned as relating to the In the prospective paradigm, subjects are aware that they are en reinforcement schedule) during the time period. Using the peak gaged in a time-estimation task. An of the animal research and most of procedure. we predict a peak-shift light. That is, we expect the peak rate the human research on duration timing have used this paradigm? In ad of responding to be temporally displaced. occurring later than when no dition to duration length itself. the most important factor influencing such information is presented. A colleague has suggested. that the op prospective duration judgments is the amount of attention to time that posite - a peak shift left - may instead occur. The reason is that the ani the subject allocates during the duration. If. for example, a concurrent mal may realize it has been distracted and may respond relatively early infoffilation-processing task is relatively easy, a subject can allocate so as not to postpone the reinforcer. For two reasons. we reject this pre more attentional resources to time, as opposed to stimulus infonnation diction. First. we hesitate to attribute complex metacognitive processes (see, for example, Block, 1992: Brown, 1 Brown & Stubbs, 1992~ to animals. Second, human evidence shows that if a concurrent task de Brown & West. 1990: Macar et aI., 1994: 11lOmas & Cantor, 1975~ mands attention, prospective duration judgment of a primary task is 1110mas & Weaver, 1975). shortened, not lengthened (Brown et aI., 1992; Brown & West, 1990; Block (1992) recently proposed a contextual-change hypothesis of Macar et aI., 1994). prospective duration judgment. TIle most important kind of infonnation Why have nearly all animal researchers failed to recognize the im influencing duration judgments is varied contextual associations, which portance of attention to time? In the case of those proposing internal may serve as time-tags. In the prospective paradigm. whenever a subject clock models, the answer seems to be that they have failed to distinguish allocates attention to time, contextual infonnation concerning the preVi between general arousal and attentional resources (Kahneman, 1973). ous act of attending to time is automatically retrieved, and a new time Proposing a separate role for attention in a modified version of a scalar tag (set of contextual associations) is encoded. Prospective duration timing model has the advantage of parsimoniously accounting for some judgment involves estimating the availability of the changes in these past findings. For example, Wilkie (1987) varied intensity of a 2-s or time-tags, or temporal context changes. 10-s light cue in a choice response task. For equal durations of the dim With only a slight modification, the contextual-change model can light and the bright light, pigeons were more likely to choose the short be seen as flUlctionally isomorphic with the attentional-gate model de response alternative following the dim light. as if the perceived duration veloped in the previous section. Figure 7 (p. 186) shows the relabeling of of a dim light is shorter than that of a bright light of equal duration. components illustrating this isomorphism. The pacemaker becomes the Wilkie suggested that stimulus intensity affects the rate of the pace context generator, the cognitive timer becomcs the context recorder, maker, an explanation in terms of general arousal. TIle problem is 'that and the cognitive comparison process becomes the context comparison this explanation introduces the possibility that a wide variety of vari process. 111e labels for other components remain the same. One major ables affect a process which Illost scalar-timing theorists assume is rela difference is that the contextual information produced by the context tively autonomous, the process underlying the rate of the pacemaker. It generator is not equivalent from moment to moment, at least not in the is lUllikely that the differences in intensity which Wilkie used would lead way that each pulse is assumed to be identical to every other pulse. TIle to different states of arousal. although Treisman (1993) also seemed to
2 I In\\'''\I('f ~('l(' 7i'l11111~r thit; vnlllT11" rh:lnf,'r 1 '1 186 Richard A. Block and Dan Zakay ;tl Models of psychological time revisited 187 context comparison process may rely on the total number of lmique judgments do not depend so much on retrieval of temporal conte>..1 in contextual associations that were encoded during the duration and that formation as on retrieval of other kinds contextual infonnation. This arc available to a memory rctrieval proccss (cf. Block, 1992). The main contextual information is encoded in association with event infornlation. advantage of this model over the attclltional-gate model is that it reveals It includes environmental, emotional, process. and other similar infor more explicit connections with othcr temporal judgment tasks. For ex ,i mation. Block (1982~ 1985: 1990: 1992; Block & Reed, 1978) proposed amplc, judgments of tile recency or serial position of an event, as well as ::1 ~i a contextual-change hypothesis of retrospective duration judgment, or the spacing of repeated or related events, seem to depend on contextual ~, I remembered duration. ll1e remembered duration of a time period length associations (Hintzman et aL, 1973: Hintzman et aL, 1975). :) 1 ens as a function of the amolUlt of contextual changes stored in memory .! 'j and available to be retrieved at the time of the duration judgment. 1 To ~ notrosPQclivo Figure 8 (p. 187) shows the components of the attentional-gate Model model (Figure 6, p. 182) or the contextual-change model of prospective duration judgment (Figure 7, p. 186) needed in a model of retrospective duration Judgment. TIle mam focus is on associations fonned, mostly automatically, as a subject attends to events (internal or external). The context generator supplies contextual infonnation, which is associated with event infonnation and stored in long-term episodic memory.
Judge i Judge 'Shorter' J Duration
Judgo 'Longer" Figure 7: ll1e contextual-change hypothesis of prospective duration judgment diagrammed as a model (after Block, 1992). Figure 8: ll1e contextual-change hypothesis of retrospec tive duration judgment diagrammed as a model Retrospective duration j udgnlent (after Block, 1992: Block & Reed, 1978). Tn contrast to the paradigms we have already discussed, in a retro Even in a retrospective paradigm, the subject occasionally attends spective duration-judgment paradigm the person is not aware lmtil after to time. On these relatively rare OCCaSlOI1S, the context recorder holds a duration has ended that the situation requires a duration judgment. infonnation about conte>..1ual changes and supplies this infonnation, This is a difficult, if not impossible, paradigm to use in nonllllman ani again in the fonn of an association to concurrent events. Infonnation mal studies (Wcardcll & Lejcune, 1993). We cannot easily give animals about contextual changes is also sent to a long-term reference memory. a shOtt vcrbal instruction, following a duratioll, to makc a retrospective ll1is component holds infomlation about the average amOlU1t of lU1ique judgment of the duratioll. Thc required training would introduce a contextual infonnation stored during durations of various length. In lengthy delay betwecn the duration and the animal's judgment. We can other words. it contains infonnation about the translation from contex ask humans, however, to make sllch a judgment. Attention to time has tual information into duration judgments (expressed verbally or other lillk Of 110 inflllPI1('e Oil retrnsl1crtive dllr:1tion jlldglllcnt. Retrospective wise) Retrospective duration judgments involve a context comparison 188 Richard A. Block and Dan Zakay Models of psychological time revisited lol) involving this information in long-term episodic memory and in long For example, anticholinesterases (e.g., physostigmine) and cholinergic tenn reference memory. receptor blockers (e.g., atropme) influence rats' perfoOllance in tile peak procedure in ways that scalar timing theOlY can elegantly handle BiOJlsychological evidence (Church, 1989: Meck & Church, 1987): The pacemaker rate (A) does not change, but the memory storage constant (K *) does. TIle parameter A variety of biopsychological evidence from both animal and hu K* is a bias on tile transfer of pulses from the accumulator to reference man experiments relates to the kinds of models discussed and proposed memory, and the value of K* may be greater or less tilan 1 depending on here (Block, 1995: Church, -1989). TIlis evidence allows a tentative such influences as cholinergic dllJgs. In humans, the remembered dura separation of brain modules or areas subserving the timer from those tion of a time period is shortened or lengthened in similar ways (Hicks, subserving memory, as well as attentional processes. 1992). Studies of individuals Witil damage to tile medial temporal lobe, FWlctioning of the intemal clock or cognitive timer seems to rely especially tile hippocampus. provide converging evidence tilat tilis brain mainly on the frontal lobes of the cerebrum, especially the dorsolateral region is intimately involved m reference memory fW1ctions (Block, prefrontal cortex. Converging evidence from psychophannacological 1995). manipulatIOns, electrophysiological recordings, and neuropsychological Exactly which areas of the brain subserve attention to time remains observations seemingly isolates the tuner to this brain regJ.on. Research lmclear. Studies using positron emission tomography reveal that several ers who have administered various drugs to animals trained on FI (i.e., anatomically separate areas of the human brain, including tile tilalamus, peak procedure) and DRL schedules suggest that dopaminergic neurons, the parietal lobes, and the anterior cingulate gyrus, play various roles in which the prefrontal cortex is known to contain, subserve the timer. For the performance of attention-demanding tasks (for a review, see Posner example, administering methamphetamine leads to a peak-shift left, as if & Raichle. 1994). TIlese areas subserve somewhat different flU1ctions, tile animal expected reinforcement sooner. The typical interpretation is which are just beginning to be clarified. TIle likely candidate for an ~rea tilat tile rate of a neural pacemaker has increased, tilereby leading to a subserving the allocation of attention to extemal events or to time (as in greater accumulation of pulses In working memory. Administering do the models shown m Figure 5, p. 181, Figure 6, p. 182, Figure 7, p. 186, pamine antagonists. such as haloperidol (which blocks postsynaptic do and Figure 8, p. 187) is the anterior cingulate gyrus. TIlis area seems to pamine receptors), conversely leads to a peak-shift right Single-cell re be tile central component of an executive attention network, which may cording from neurons in the prefrontal cortex reveals some that are ac directly influence.the working-memory functions of the dorsolateral pre tive in tile interval between tile onset of a stimulus and tile time an frontal cOltex. However, tile present evidence is too incomplete to sug organism may emit a response (for reviews, see Fuster, 1987; 1989). In gest anything more definitive about brain components subserving tile humans, damage to tilis region of tile prefrontal cortex disrupts various role of attention in tile cognitive models of time we have reviewed and tinung flmctions, including discriminating tile recency and temporal or proposed here. der of events (Milner et aI., 1985: 1990: 1991). However, none of tilis evidence shows tilat it is necessary to postulate an autonomously fW1C Summary and conclusions tioning, repetitive pacemaker as tile fi rst component III duration timing, such as in several models we have discussed here (Figure 3, p. 176, Fig Timing-witil-a-timer models asselt that a pacemaker, part of an in ure 4, p. 177, and Figure 6, p. 182). As ivlilner et al. (1990) argue, tile ternal clock, underlies psychological timing. Timing-witilOut-a-timer evidence may be more consistent with the notion tilat the dorsolateral models propose instead that psychological time is constructed from prefrontal cOltex automatically generates contextual infornlation .which processed and stored infonnation. TIle scalar-timing model, the best ex may serve as time tags (Figure 7, p. 186, and Figure 8, p. 187). ample of timing witil a timer, can explain much of tile animal data and some of the human data on time-related behavior and judgment. How Other evidence reveals that other brain regions mediate reference ever, it is not easily able to explain why cognitive factors influence tem memory for temporal (duration) information. The hippocampus and as poral behavior and judgment. In order to handle tilese factors, we pro sociated medial temporal lobe structures are influenced by cholinergic posed a modified model that incorporates an attentional process. 111is agonists and antagonists. Administering drugs tilat influence cholinergic model, the attentional-gate model, is needed to explain findings in which neurons shortens or lengthens the remembered duration of a time period. 191 190 Richard A. Block and Dan Zakay Models of psychological time revisited humans divide attention between temporal and nontemporal infonnation. Block, R.A. (1995). Psychological time and memory systems of the brain. In 1.T. Fraser & M.P. Soulsby (Eds.), Dimensions of time It also explains and predicts some analogous findings in animal research. and ltfe: the study o.f time VIII (pp. 61-76). Madison, CT: Interna The attentional-gate model is roughly isomOtvhic widl a contextual tional Universities Press. ' change model of prospective duration judgment. This model, which in Block, R.A., & Reed, M.A. (1978). Remembered duration: Evidence for volves timing without a timer~ replaces the pacemaker mechanism with a a contextual-change hypothesis. Journal o.f Experimental Psy process that generates varied contextual information. Temporal context chology: Human Learning & lv/emory, 4, 656-665.' . changes, stored as contextual associations with ongoing events, may therefore underlie prospective duration judgments. A modification of this Brown, S.W. (1985). Time perception and attention: the effects of pro model can also explain retrospective duration judgments, which are more spective versus retrospective paradigms and task demands on per typIcally explained by proposing cognitive models. ceived duration. Perception & Psychophysics, 38, 115-124. Biopsychological evidence from both animal and human experi Brown, S.\V .. & Stubbs, D.A. (1992). Attention and interference in pro ments relates to the models reviewed. The areas of the brain that are spective and retrospective timing. Perception, 2], 545-557. heavily implicated in variolls aspects of time-related behavior and judg Brown. S. W., Stubbs, D. A.. & West, A. N. (1992). 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