One Thing Follows Another - American Psychological Association

Developmental Psychology 1989. Vol. 25. No. 2, 197-206

Copyright 1989 by the American Psychological Association. Inc. 0O12-1649/89/SOO.75

One Thing Follows Another: Effects of Temporal Structure on 1- to 2-Year-Olds' Recall of Events Patricia J. Bauer and Jean M. Mandler

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University of California, San Diego Investigated whether recall of events by children under 2 years of age is similar to that of older preschoolers and adults. Experiment 1 used elicited-imitation to test 16- and 20-month-olds' immediate and delayed recall (2-week delay) of familiar and novel events. Ordered recall at immediate and delayed test was superior for familiar events and for novel events with causal relations among the elements; ordered recall of novel events lacking causal relations was significantly lower. Experiment 2 tested children's sensitivity to differences in underlying structure of novel events. Nineteen-, 25-, and 31 -month-olds organized recall around causal relations, in spite of experimental manipulations that interrupted causally connected pairs of elements. The experiments provide clear evidence that, like preschoolers and adults, children as young as 16 months include temporal order information in their representations of both familiar and novel events and that the causal structure of novel events influences their recall.

Research on children's memory has amply demonstrated that when children are working in a familiar and meaningful context, they exhibit memory skills far more advanced than they do when working in an unfamiliar context stripped of meaning. This lesson provided the impetus for research on children's memory for everyday events and routines. By interviewing 3- to 8-year-old children about their participation in everyday events, Nelson and her colleagues (e.g., Nelson, 1986; Nelson & Gruendel, 1981,1986) have shown that children as young as 3 years of age recall events in a fashion similar to that of older children and adults. The apparent similarities in the structure underlying the event representations of preschoolers and adults has led to the question of whether the event representations of even younger preverbal and early verbal children are similar as well. It is this question that provides the focus for the present research. In their responses to questions about "what happens" in the course of everyday events and routines, younger children tend to mention fewer components of an event compared with older children. However, they almost invariably mention the main or central act (e.g., "eating" in a meal associated event), and at all

ages they almost invariably mention the components of an event in their usual or canonical order (Nelson & Gruendel, 1981,1986). What is more, after only a single experience of an event, kindergartners (Smith, Ratner, & Hobart, 1987) and 3to 7-year-old children (Hudson, 1986) provide well-ordered accounts of it. With repeated experience of an event, narratives about it become more elaborate and more hierarchically organized (Fivush & Slackman, 1986). Finally, children recall aspects of events with causal and temporal in variances more frequently and at a younger age than they do aspects of events lacking such structure (Hudson & Nelson, 1983; Slackman, Hudson, & Fivush, 1986).1 In contrast to the rich data base on preschoolers' representation and recall of events, we have very little data on event representation and recall in younger, preverbal and early verbal children. From the symbolic play literature we know that children spontaneously combine two actions into an ordered sequence at 24 months of age (Fenson & Ramsay, 1980) and that the number of ordered actions that children produce in elicited play doubles between 20 and 28 months of age (Shore, O'Connell, & Bates, 1984). However, we know little else about the development of event representation in children under 2 years of age and we know virtually nothing about the organization of their recall of events. In the present research, we focus on three ques-

Portions of these data were presented as a poster, "Factors Affecting Very Young Children's Recall of Events," at the biennial meetings of the Society for Research in Child Development, Baltimore, April 1987. This research was supported in part by grants from the MacArthur Foundation Network on the Transition from Infancy to Early Childhood and by National Science Foundation Research Grants BNS8109657 and BNS-8510218. We thank Debby Kirschenbaum, Una Lynch, Laraine McDonough, Susan Oh, Inez Poza-Juncal, and Elisabeth Vangsness for their help on various stages of this project. We thank Alan Leslie and Andrew Meltzoff for suggesting some of the manipulations used in these experiments. Correspondence concerning this article should be addressed to Patricia J. Bauer, Department of Psychology, C-009, University of California, San Diego, La Jolla, California 92093.

' Items in a sequence are arbitrarily ordered when there is nothing inherent in the items to dictate their position in the sequence. For example, you may put on your coat either before or after putting on your hat. Causal relations exist when one item in a sequence must be performed before another in the same sequence. For example, you must open the door before you can go through it. In this example, as in the others to be described, the relation would be more appropriately described as enabling rather than as causal. That is, opening the door does not cause one to go through it. However, it does make the next step possible. We will adopt the vocabulary of those working in this area and refer to these relations as "causal." Regardless of whether these relations are truly causal or merely enabling, they imply temporal invariance. 197


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PATRICIA J. BAUER AND JEAN M. MANDLER

tions. All three questions deal directly with the issue of whether the event representations of very young children share characteristics with those of older preschool children. First, do very young children include temporal-order information in their representations of familiar events? Second, do they use order information to organize their recall of newly experienced events? Third, do they organize their recall around causal relations? On conceptual grounds, Mandler (1984) and Nelson (1986) have argued that in their earliest representations of events, children include information both about the components and the order in which the components occur. However, some researchers have argued that the event representations of children 2 years of age and younger are not temporally organized. Case and Khanna (1981), for example, have speculated that general changes in information-processing capacity occur around 24 to 28 months of age. These changes allow children to coordinate multiple pieces of information and, thus, make temporal ordering as an organizing principle available for the first time. This conceptualization predicts that the event representations of very young children are not temporally ordered, but, rather, are unorganized collections of individual components. Data reported by O'Connell and Gerard (1985) would appear to support the view that early event representations are unorganized. They used an elicited-imitation technique to obtain information about 20- to 36-month-old subjects' immediate recall of events. Elicited imitation involves modeling an action or sequence of actions and then encouraging the subject to imitate. The technique is useful for working with children with limited verbal capabilities. O'Connell and Gerard presented subjects with 18, three-element sequences depicting familiar events. One-third of the events were presented in their canonical or usual order (e.g., take off a bear's shirt, put the bear in the tub, wash the bear); one-third were presented in reverse order (e.g., wash the bear, put it in the tub, take off its shirt); and onethird were scrambled versions of unrelated but meaningful actions (e.g., wipe the bear's mouth, the bear pays money, cover the bear with a blanket). Their 20-month-old subjects were only able to reproduce the components of the familiar and the reverse-order sequences; they indicated little or no ability to reproduce the modeled order of any of the sequence types. The 24-month-olds were able to reproduce the modeled order of the sequences only when they were familiar and presented in their canonical order. The 28-month-olds produced both canonical and reverse-order sequences in canonical order. That is, they "corrected" or "repaired" the reverse sequences. The 36month-olds were better able to reproduce the modeled order of all of the sequence types. In sum, the use of temporal ordering as an organizing principle was not evident until 24 months of age, and then only when the events depicted were familiar. The work by O'Connell and Gerard (1985) represented a significant contribution to a virtually nonexistent literature on event representation and recall in children under 3 years of age. However, for methodological and conceptual reasons, the data make it difficult to draw conclusions about children's abilities to use temporal information to order their recall. We have discussed our reservations about this work elsewhere (Bauer & Mandler, in press; Bauer & Shore, 1987) and will mention them only briefly here. First, the subjects were required to imitate a

total of 18 event sequences, two-thirds of which were "unusual." We would like to be able to use children's responses to new sequences as an indication of their ability to use temporal order information to organize recall of novel events. However, the new sequences consisted of novel concatenations of components of familiar events. Thus, the events violated expectations about order that children may have already formed. Truly novel events are those for which one has no order expectations. Second, O'Connell and Gerard's unusually high attrition rate in their youngest age group, 65% of whom were dropped from the sample for lack of participation, speaks to the disturbing effect that such violations have on young subjects. It is likely that the high density of sequences involving violations of real-world knowledge had a detrimental effect on performance across the board. Third, it is difficult to evaluate the children's abilities to engage in ordered imitation of the familiar event sequences because the subjects saw both forward and reverse-order presentations of the same event within a single experimental session. We know on the basis of adult work that presentation of conflicting order information within an experimental session has a detrimental effect on recall of temporal order. Therefore, we argue that the subjects' responses to the familiar-canonical sequences do not represent an adequate test of children's abilities to engage in ordered recall of familiar events. A genuine test of children's responses to familiar event sequences requires that they be presented with familiar events in their canonical order only. To evaluate whether they include order information in their representations of newly experienced events, it is necessary to present them with sequences of events that are truly novel and do not violate any existing real-world knowledge. Furthermore, to evaluate whether very young children are likely to organize their event representations around causal and temporal invariances, it is necessary to contrast novel sequences of events lacking causal relations with novel sequences of events containing causal relations. Novel sequences are necessary in order to separate the effects of familiarity from the effects of the causal relations themselves. In a recent study by Bauer and Shore (1987), elicited imitation of event sequences was used to investigate event recall in a sample of 21-month-old children. Three different types of sequences were presented. To assess whether very young children use temporal information to order their recall of familiar events, one relatively familiar event sequence in its canonical order (i.e., giving a teddy bear a bath) was presented. To assess response to novel sequences, two coherent but completely new sequences were presented. One of the novel sequences was characterized by causal relations among the elements (i.e., making a rattle of two nesting cups and a rubber ball), and the other novel sequence lacked causal relations among the elements (i.e., banging, turning, and stacking a ring on a dowel stick). We tested both immediate and delayed recall of the individual components of the sequences as well as their temporal order. The subjects demonstrated clear evidence of both immediate and delayed recall (6-week delay) for both the components and their temporal order for the familiar and the novel-causal sequences. In contrast, subjects showed no evidence of immediate or delayed recall for either the individual actions or the temporal order of the actions in the novel sequence lacking causal relations (i.e., novel-arbitrary sequence).

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ONE THING FOLLOWS ANOTHER

The results of Bauer and Shore (1987) stand in contrast to those of O'Connell and Gerard (1985) and indicate that even very young children include information about temporal order in their representations of familiar events. Furthermore, the data indicate that young children encode temporal information in their initial representations of certain types of event sequences, namely, those with causal relations among the elements. The differences in recall between the novel-causal and the novel-arbitrary sequences suggest that young children may be differentially sensitive to the organization underlying event sequences from their very first experience of them. However, this conclusion must be drawn with caution. First, the data were based on only one sequence of each type. Second, subjects' lack of adherence to the target order in the novel-arbitrary task may have been artificially low, primarily because of their lack of production of the individual target components, not because of the nature of the temporal connections among the components. Thus, further investigation of these effects is warranted. In thefirstof two experiments, we extended the study of early event representation and recall to even younger children: 16and 20-month-olds. We tested both immediate and delayed recall (2-weeks) for three-element event sequences of the types tested in Bauer and Shore (1987): familiar, novel-causal, and novel-arbitrary. In Experiment 1 of the present study we included two sequences of each type, including two new novelarbitrary sequences. The new novel-arbitrary sequences were specifically designed to increase the likelihood of production of the individual target components. Thus, we expected a higher level of production of the target elements with the new sequences, relative to that observed in Bauer and Shore. In other respects, we expected a replication of Bauer and Shore. That is, we expected that immediate and delayed recall for the temporal order of the events would be superior for the familiar sequences and for the sequences characterized by causal or enabling relations among items compared with the arbitrarily ordered sequences. No specific pattern of differential recall was expected for the familiar as compared with the causal sequences. Experiment 2 involved a further exploration of the influence of causal organization on recall of event sequences. Differential levels of recall for novel-causal as compared with novel-arbitrary event sequences raise the possibility that children are sensitive to causal relations even in the absence of information about the sequences' usual temporal variance or invariance. Perhaps subjects use causal relations as an organizing principle from their very first experience with a causally related event. That is, children may not simply construct a linear representation of a causally related event sequence, but, rather, one that is organized around the causally related elements. No such organizational scheme is available in an arbitrarily ordered event sequence. If causally related pairs of elements do enjoy a privileged organizational status relative to merely temporally ordered elements, we might expect to see differential displacement of an irrelevant element inserted in the middle of a causally related pair of elements compared with an arbitrarily ordered pair. In Experiment 2 we introduced an irrelevant component into one causally related sequence and into one arbitrarily ordered sequence. For the causal sequence, we expected to observe correct ordering of the causal portion of the sequence and displacement of the irrelevant component. For

the arbitrary sequence no specific pattern of differential displacement of the irrelevant component was predicted.

Experiment 1 Method Subjects. Twenty children with a mean age of 16 months, 15 days (range = 16 months, 2 days to 16 months, 25 days) and 20 children with a mean age of 20 months, 16 days (range = 20 months, 3 days to 20 months, 29 days) participated as subjects. In the 16-month age group there were 10 girls and 10 boys; in the 20-month age group there were 11 girls and 9 boys. All of the subjects were seen in the laboratory for two visits that were separated by 2 weeks (the mean number of days between visits was 14.9 for the 16-month age group and 14.1 for the 20-month age group). Subjects were recruited from an existing pool of volunteer parents who had responded to advertisements in local newspapers. An additional four 16-month-olds and two 20-months-olds were tested at Session 1 but were excluded from the final sample because they failed to return in time for the Session 2 visit. All children were given a small gift for their participation. Procedure. Subjects were invited into a laboratory set up as a playroom. After a brief warm-up period they were seated in a booster seat or on their parents' lap across the table from the experimenter. One of the parents remained in the room throughout the session. Parents were asked not to suggest behaviors to their children or to "assist" them by reminding them of the next step in a sequence. Two warm-up sequences, designed to accustom the subjects to the elicited-imitation procedure, were administered prior to beginning the test sequences. The warm-up sequences consisted of: (a) rolling a ball across the table and then placing it on a box and (b) drinking from a toy cup and then placing it on a saucer. There were six test sequences presented to each subject: two familiar sequences, two novel-causal sequences, and two novel-arbitrary sequences, each involving three components. The sequences were as follows: 1. Familiar—Bath. The subject was presented with a stuffed bear that was dressed in a T-shirt and with a sponge and a plastic dishpan. The experimenter (E) modeled taking off the bear's shirt, putting the bear in the tub, and "washing" the bear. 2. Familiar—Clean the table. The subject was presented with a small wastebasket, a paper towel, and an empty spray bottle. E modeled spraying the table, wiping it with the towel, and throwing the towel away.2 3. Novel-causal—Rattle. The subject was presented with two graduated nesting or stacking cups and a small rubber ball. E modeled putting the ball in the larger cup, inverting the smaller cup into the larger, and shaking the cups. 4. Novel-causal—Frogjump. The subject was presented with a small wooden board, a wedge-shaped block, and a toy frog. E modeled putting the board on the base to form a teeter-totter, placing the frog on the end ofthe board, and hitting the board (thereby causing the frog to "jump"). 5. Novel-arbitrary—Train ride. The subject was presented with two train cars that could be attached with Velcro, a small doll to fit in the cars, and a piece of train track. E modeled attaching the cars to one another, putting them on the track, and putting the doll into one of the cars. 6. Novel-arbitrary—Make a picture. The subject was presented with a small chalkboard, an easel, a piece of chalk, and a sticker. E modeled

2 The clean-the-table sequence was selected as one of the familiar events on the basis of pilot work conducted for a separate study (Mills, Mandler, Schreibman, & Oke, 1988).


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putting the sticker on the board, leaning the board against the easel, andjects. Where appropriate, Tukey tests of significant difference drawing on the board with the chalk.' (p < .05) were used to examine main effects and interactions. For each sequence the subjects first were allowed to manipulate the Descriptive statistics for the mean number of different target props to be used prior to modeling of the sequence. This provided a actions produced and the mean number of different pairs of baseline measure of the spontaneous occurrence of the targeted behavactions produced in the target order for all three sequence types iors. Then, the sequence of actions was modeled, with narration, two are presented in Table 1. A 2 (age: 16 months, 20 months) X times in succession. The experimenter encouraged exact imitation with 3 (sequence type: familiar, novel-causal, novel-arbitrary) X 4 instructions such as "Can you give the dirty bear a bath just like I did?" (recall condition: baseline, Postmodeling 1, Premodeling 2, The subjects' postmodeling performance constituted immediate recall. Postmodeling 2) mixed analysis of variance (ANOVA) was conAll 40 subjects returned to the laboratory 2 weeks later, and the proceducted for both dependent variables.4 dure was repeated. Prior to modeling, the subjects were simply given the props with no instruction. Procedurally, this condition was identical There were statistically significant main effects of age, sewith the spontaneous or baseline condition at Session 1. After modeling, quence type, and recall condition. There also were several sigthe subjects were again encouraged to imitate the model exactly. At the nificant interactions, which will be discussed below. For the second session the children's performance prior to modeling constimain effect of age, across sequence types and recall conditions, tuted delayed recall, whereas their postmodeling performance constithe 20-month-old subjects produced more of the target compotuted relearning. Neither the subjects nor their parents were led to exnents, P( 1,38) = 12.31, p < .001, and showed greater adherence pect that the tasks would be presented again at Session 2. to the target order, F\l, 38) = 13.73, p < .001, than did the 16The sequencing task was one of several tasks administered during month-old subjects. The differences are not the result of differeach 45- to 60-min experimental session. To lessen fatigue with the task, ential levels of the spontaneous occurrence of the target behavthree sequences (one of each type) were administered, then subjects eniors. That is, there were no differences in the level of baseline gaged in another, unrelated task, and then the remaining three sequences were administered. To simplify counterbalancing, Bath, Frog performance between the 16- and 20-month-old subjects. Thus, jump, and Make a picture were always presented together, and Clean the age effects represent differences in amount recalled. the table. Rattle, and Train ride were always presented together. Each Second, there were statistically significant main effects of sesequence was presented approximately equally often in each serial posiquence type for both dependent variables. Across age groups tion. For each subject, the sequences were presented in different orders and recall conditions, subjects recalled significantly more comat Sessions 1 and 2. The sessions were videotaped for later analysis. ponents of the novel-causal sequences than of the familiar seScoring. Two raters were trained together on an existing corpus of quences. Recall of the components of the novel-arbitrary sesequencing data. They established reliability at 90% or above on three quences was intermediate and did not differ significantly from successive subjects. One rater then watched videotapes of the sessions the other two sequence types, F{2,76) = 6.33, p < .003. In terms and created a list of the children's behaviors, indicating occurrence of of adherence to target order, a different relative order was evitarget behaviors for all 40 subjects at both Sessions 1 and 2. The second rater then independently coded 18 randomly selected sessions (23% of dent. Subjects were most likely to order the components corthe total sample). Agreement between the two raters was 92% (range = rectly in the novel-causal condition, followed by the familiar 86%-100%). For each sequence, one of the authors then calculated the condition, andfinallyby the novel-arbitrary condition. The levnumber of different target actions produced and the number of different els of performance on each of the sequences types differed sigpairs of actions produced in the target order. For example, on the novelnificantly from one another, FQ., 76) = 18.44, p < .001. Thus, causal Rattle task one subject produced the following actions: She put the ball in the small nesting cup, "poured" the ball from the small cup 5 For the novel-arbitrary events there is a total of six possible orders to the larger, inverted the small cup into the larger, and shook the cups. of presentation. To keep the number of subjects to a minimum, we seShe produced all three target actions (ball into cup, invert small cup lected only one order for each sequence. The order selected was intended into larger, shake cups) and produced two different pairs of actions in to minimize preexisting tendencies or biases and, as much as possible, the target order: (a) ball into cup and invert cup and (b) invert cup and to be neutral with respect to expectations of order for events. Of course, shake cups. The former provided a measure of the child's production we had no assurance that we would be successful. Nevertheless, a qualiof the elements of the sequence, whereas the latter indicated the degree tative analysis of the orders produced by the subjects indicated that we to which ordering was evident. It should be noted that the number of were. For both novel-arbitrary sequences, all possible orders of reproelements produced affects the production of pairs of actions in the target duction were observed at least once (this includes the six possible orders order. Thus, the two dependent measures are not independent of one of all three components as well as the six possible orders of only two another. components). There was no consistent tendency for any single order These measures were calculated for subjects' premodeling or baseline other than the modeled one (or subportions of it) to be produced. performance at Session 1, postmodeling performance at Session 1, pre4 Subjects' premodeling performance at Session 1 provided a baseline modeling performance at Session 2, and postmodeling performance at measure of performance, that is, the amount of targeted behavior that Session 2. In the discussion to follow, subjects will be said to have demwould occur spontaneously. One way to analyze the data would have onstrated: (a) immediate recall, if Postmodeling 1 measures were sigbeen to subtract the level of baseline performance from each of the meanificantly greater than measures of baseline; (b) delayed recall, if Presures of recall, thereby creating a difference score reflective of changes modeling 2 measures were significantly greater than measures of basein performance after exposure to the modeled event. Difference scores line; (c) forgetting, if Premodeling 2 measures were significantly lower were calculated and subjected to 2 (age) X 3 (sequence type) X 3 (recall than Postmodeling 1 measures; and (d) additional learning, if Postmodcondition: Postmodeling 1, Premodeling 2, Postmodeling 2) analyses of eling 2 measures were significantly greater than Postmodeling 1 meavariance. Analyses of the difference scores and analyses of the raw scores sures. did not differ from one another. Because inclusion of the baseline meaResults sure enables direct assessment of amount of recall (i.e., differences bePreliminary analyses revealed no reliable gender differences. tween baseline and postmodeling measures), we report the analyses including baseline measures of performance. Subsequent analyses were based on the entire sample of 40 sub-

ONE THING FOLLOWS ANOTHER

Table 1 Experiment 1: Mean Number ofDifferent Target Actions and Mean Number ofDifferent Pairs of Actions in Target Order Baseline Subjects/ sequence type

M

SD

Immediate recall M

SD

Delayed recall M

Additional learning

SD

M

SD


Number of different target actions a 16-month-olds Familiar Causal Arbitrary 20-month-olds Familiar Causal Arbitrary

.35 .68 .80

.46 .41 .57

2.10 2.15 1.88

.48 .65 .36

1.28 1.63 1.43

.53 .72 .54

2.35 2.63 2.05

.54 .43 .58

.33 .78 .88

.37 .47 .69

2.50 2.63 2.38

.51 .48 .39

1.88 1.93 2.05

.97 .65 .51

2.43 2.68 2.65

.52 .49 .37

Number of different pairs in target orderb 16-month-olds Familiar Causal Arbitrary 20-month-olds Familiar Causal Arbitrary

.03 .13 .15

.11 .22 .24

.83 .98 .70

.49 .55 .30

.33 .48 .20

.29 .50 .25

1.10 1.45 .55

.45 .56 .46

.50 .20 .13

.15 .30 .28

1.25 1.43 .73

.60 .59 .50

.90 .80 .55

.75 .52 .48

1.23 1.60 1.05

.64 .50 .32

" The maximum number is 3. b The maximum number is 2.

although subjects were producing an approximately equal number of the components of the novel-arbitrary sequences relative to the other two sequence types, they were significantly less likely to produce them in the correct order. Third, there were statistically significant main effects of recall condition both for the number of target actions, F(3, 114) = 351.02, p < .001, and for the number of pairs of actions in the target order, F{3,114)= 186.83, p