Experimental Methods in Studying Child Language Acquisition Ben Ambridge∗ and Caroline F
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by MPG.PuRe Advanced Review Experimental methods in studying child language acquisition Ben Ambridge∗ and Caroline F. Rowland This article reviews the some of the most widely used methods used for studying children’s language acquisition including (1) spontaneous/naturalistic, diary, parental report data, (2) production methods (elicited production, repeti- tion/elicited imitation, syntactic priming/weird word order), (3) comprehension methods (act-out, pointing, intermodal preferential looking, looking while lis- tening, conditioned head turn preference procedure, functional neuroimaging) and (4) judgment methods (grammaticality/acceptability judgments, yes-no/truth- value judgments). The review outlines the types of studies and age-groups to which each method is most suited, as well as the advantage and disadvantages of each. We conclude by summarising the particular methodological considerations that apply to each paradigm and to experimental design more generally. These include (1) choosing an age-appropriate task that makes communicative sense (2) motivating children to co-operate, (3) choosing a between-/within-subjects design, (4) the use of novel items (e.g., novel verbs), (5) fillers, (6) blocked, coun- terbalanced and random presentation, (7) the appropriate number of trials and participants, (8) drop-out rates (9) the importance of control conditions, (10) choos- ing a sensitive dependent measure (11) classification of responses, and (12) using an appropriate statistical test. © 2013 John Wiley & Sons, Ltd. How to cite this article: WIREs Cogn Sci 2013, 4:149–168. doi: 10.1002/wcs.1215 INTRODUCTION them to select those that are most useful for studying particular phenomena. istorically, much influential work in the domain While few modern researchers would argue that of child language acquisition has consisted of H children’s linguistic performance is largely irrelevant what one might call paper-and-pencil theorizing. to their competence, it is true that it is impossible to Indeed, it has been explicitly argued that linguistic investigate children’s knowledge directly, and that this performance (i.e., what children say and do) bears must be somehow inferred from observable behavior. such an indirect relationship to linguistic competence To be sure, performance on any experimental task (i.e., what children know) that the former is essentially will be affected by both specific task demands (e.g., useless as a diagnostic of the latter.1 Currently, the ability to manipulate toys or to point to a partic- however, a consensus seems to be developing that all accounts of language acquisition phenomena, from ular video screen) and by general limitations such as whatever theoretical perspective, must be judged attention and memory. The appropriate response to primarily on their ability to explain actual data this situation is not to abandon experimental studies collected from children and adults. Consequently it altogether but (1) to seek converging evidence from is useful for researchers to be familiar with as wide multiple paradigms and (2) to build into study-designs a range as possible of the experimental methods used controls that allow particular task demands to be fac- in studying language acquisition, in order to enable tored out. Suppose, for example, a study finds that children of a particular age are unable to produce a Conflict of interest: The authors declare no conflict of interest. particular type of passive sentence. In order to rule ∗Correspondence to: [email protected] out the possibility that children of this age are simply University of Liverpool, Institute of Psychology, Health & Society, unable to produce sentences of this length in general University of Liverpool, Liverpool, UK (for example due to memory limitations), a suitable Volume 4, March/April 2013 © 2013 John Wiley & Sons, Ltd. 149 Advanced Review wires.wiley.com/cogsci control would be to include a condition where chil- available (see, e.g., http//:childes.psy.cmu.edu). How- dren attempt to produce an active sentence of the same ever, analyses must be conducted with care in order length. to take account of sampling constraints. Typically The aim of the present review is to provide recording regimes are no more frequent than around a comprehensive outline of the major methods used 1 h/week,10 and often considerably less frequent,11,12 in acquisition research, to evaluate their strengths although one research group is currently engaged in and weakness, and to highlight a number of current a project to transcribe all the conversation taking methodological controversies, particularly in the areas place within a household.12 Thus far from provid- of study design and statistical analysis. The methods ing a direct window on what children say and hear, are grouped into naturalistic, production, comprehen- spontaneous-speech methods provide a tiny sample, sion,andjudgment paradigms, although many studies and failing to account for this fact can result in erro- combine elements of each. For example, researchers neous conclusions. For example, consider the ongoing might use a naturalistic corpus analysis to select items debate over whether 2-year-old children show full for a production study2,3 or a parental-report measure productivity with determiners (which, if so, is argued to select participants for a comprehension study.4,5 to constitute support for generativist over construc- Although the example studies given are mostly from tivist accounts of acquisition).13–16 The question is, the domain of syntax and morphology, the major- essentially, whether every noun that occurs with a in a ity of studies in many other domains of language particular child’s speech also occurs with the.Itiseasy acquisition research (e.g., word-learning, phonology, to see how thinly sampled data could underestimate pragmatics) use one or other of the paradigms dis- productivity, for example by recording the + ball but cussed here (broadly defined). We have not included missing uses of a + ball. Somewhat less intuitively, a separate section on standardized tests such as the thin sampling can also overestimate productivity,17 Clinical Evaluation of Language Fundamentals6 the in this case by capturing frequent nouns that the Test of Early Language Development7 or the Peabody child uses with both the and a, but missing less fre- Picture Vocabulary test8 because all use some variant quent nouns that occur only with one or other of the of the methods outlined here (e.g., elicited production, determiners. comprehension, etc.). However, it is worth bearing in One way to address this issue is to use the mind that they may be useful for selecting children caregiver’s speech as a control, randomly deleting to participate in a study, or for matching groups in utterances so that the corpus is matched in size to that between-subjects designs. of the child.18 If, with this control in place, adults (who can be assumed to have a fully productive system) appear to show no greater productivity than children, SPONTANEOUS NATURALISTIC this would suggest that apparent effects of lexical- SPEECH, DIARY & PARENTAL REPORT specificity are in fact caused entirely by thin sampling. Another potential solution is to calculate how often DATA particular combinations (e.g., the + ball) would be Perhaps the simplest method for studying language expected to occur, given the independent frequencies development is simply to record children’s sponta- of the individual items (e.g., the and ball19). This neous speech, in conversation with caregivers. Indeed, is particularly informative when evaluating theoreti- the analysis of spontaneous speech data is often con- cal accounts that predict that particular combinations trasted with ‘experimental’ methods. The paradigm is (e.g., him + plays) will be entirely absent.20 Athird included here because the collection and analysis of approach is to attempt to address the sampling issue such data requires many of the same decisions regard- at the design stage. For many theoretical questions, it ing design and controls as other paradigms. Indeed, may be that a sampling regime of, for example, 2 h/day asking caregivers to spend long periods devoted solely for 13 consecutive days is much more informative than to conversation with their children is far from ‘natural- a sample of 1 h/fortnight spread over the course of istic’ (though some studies have attempted to address a year. Of course, for phenomena with an important this problem by sampling at random throughout the developmental aspect, the reverse will be the case. day9). The point is that, ideally, samples should be collected Naturalistic speech analysis can be very cost- with a particular theoretical question in mind, which effective in the long-term. Although data transcription allows the recording regime to be tailored to that and collection is initially very time-consuming, the purpose. A fourth alternative is to eschew sampling resulting dataset can be used multiple times both by in favor of a diary method that attempts to capture the original researchers and by others if made publicly all instances of a particular structure, as has been 150 © 2013 John Wiley & Sons, Ltd. Volume 4, March/April 2013 WIREs Cognitive Science Experimental methods in studying child language acquisition attempted for questions,21 basic argument structure around these experiment subtypes, although it should constructions22 and individual verbs.23,24 It is impor- be borne in mind that one often blends into another tant to bear in mind, however, that even full sam- in particular studies. pling—or the most assiduous diarist—does not record everything that the child could say, only everything that she does say. Thus, if the goal is to investigate Elicited Production acquisition of less frequent (or novel) items and struc- If the analysis of spontaneous speech data is the tures, then additional, less naturalistic paradigms will ‘default’ paradigm in language acquisition research be needed. then a family of methods known as ‘elicited Another measure based on children’s sponta- production’ runs a close second.