Generalizing the dynamic field theory of the A-not-B error beyond infancy: three-year-olds' delay- and experience-dependent location memory biases

Thelen and colleagues recently proposed a dynamic field theory (DFT) to capture the general processes that give rise to infants' performance in the Piagetian A-not-B task. According to this theory, the same general processes should operate in noncanonical A-not-B-type tasks with children older than 12 months. Three predictions of the DFT were tested by examining 3-year-olds' location memory errors in a task with a homogeneous task space. Children pointed to remembered locations after delays of 0 s to 10 s. The spatial layout of the possible targets and the frequency with which children moved to each target was varied. As predicted by the DFT, children's responses showed a continuous spatial drift during delays toward a longer term memory of previously moved-to locations. Furthermore, these delay-dependent effects were reduced when children moved to an "A" location on successive trials, and were magnified on the first trial to a nearby "B" location. Thus, the DFT generalized to capture the performance of 3-year-old children in a new task. In contrast to predictions of the DFT, however, 3-year-olds' responses were also biased toward the midline of the task space-an effect predicted by the category adjustment (CA) model. These data suggest that young children's spatial memory responses are affected by delay- and experience-dependent processes as well as the geometric structure of the task space. Consequently, two current models of spatial memory-the DFT and the CA model-provide incomplete accounts of children's location memory abilities.     

Young Children's Comprehension of Pretend Episodes: The Integration of Successive Actions

In 3 experiments, children's comprehension of successive pretend actions was examined. In Experiment 1, children (25–38 months) watched 2 linked actions (e.g., a puppet poured pretend cereal or powder into a bowl, and then pretended to feed the contents of the bowl to a toy animal). Children realized that the pretend substance was incorporated into the second action. In Experiment 2, children (24–39 months) again watched 2 linked actions (e.g., a puppet poured pretend milk or powder into a container, and then pretended to tip the contents of the container over a toy animal). They realized that the animal would become "milky" or "powdery." In Experiment 3, children (25–36 months) drew similar conclusions regarding a substitute rather than an imaginary entity. The results are discussed with reference to children's causal understanding, their capacity for talking about objects and events in terms of their make-believe and real status, and the processes underlying pretense comprehension.     

Waiting to Use a Symbol: The Effects of Delay on Children's Use of Models

To use a symbol to solve a problem, children must achieve representational insight; they must realize that the symbol stands for its referent. Moreover, they must keep this relation in mind as they attempt to use the symbol. The present studies investigated the achievement and maintenance of representational insight. 3-year-olds were asked to use a scale model of a room to find a toy hidden in the room. In Study 1a, children first watched as a small toy was hidden in the model. They then waited either 20 sec, 2 min, or 5 min before attempting to find a similar, larger toy that was hidden in the corresponding place in the room. All children experienced all delay intervals; three groups experienced the delays in different orders. There was a dramatic effect of delay order. The children who experienced the 20-sec delay on their first trial generally performed well throughout the 6 trials, but the children who experienced a 5-min delay first almost always failed to find the toy in the room, even on subsequent trials with shorter delays. Additional studies revealed that the negative effects of the initial long delay could be overcome by providing reminders of the model and its relevance (Studies 2 and 3) or by giving children prior experience in using the model (Study 4). The results indicate that keeping a symbol-referent relation in mind can be difficult for 3.0-year-old children. This research is discussed in terms of the importance of maintaining representational insight.     

Physical Similarity and Young Children''s Understanding of Scale Models

Young children's understanding of the correspondence between a scale model and a larger space is affected by the degree of physical similarity between the 2 spaces. In 4 studies, children between 2.5 and 3.5 years of age watched as a miniature toy was hidden somewhere in a scale model of a room. They were then asked to find an analogous toy that was hidden in the corresponding place in the room itself. The effects of different levels of 3 types of physical similarity were investigated. In general, the children's retrieval scores increased as a function of increasing similarity, although younger children required a higher degree of similarity to appreciate the model-room correspondence than did older children. Some types of similarity were more important than others: The level of similarity between the objects within the 2 spaces and of the overall size of the spaces both had large effects on the children's performance. Similarity presumably affects accessibility, the likelihood that children's representation of one space will provide access to their representation of the other space.     

Infant search and object permanence: a meta-analysis of the A-not-B error

Research on Piaget's stage 4 object concept has failed to reveal a clear or consistent pattern of results. Piaget found that 8-12-month-old infants would make perserverative errors; his explanation for this phenomenon was that the infant's concept of the object was contextually dependent on his or her actions. Some studies designed to test Piaget's explanation have replicated Piaget's basic finding, yet many have found no preference for the A location or the B location or an actual preference for the B location. More recently, researchers have attempted to uncover the causes for these results concerning the A-not-B error. Again, however, different studies have yielded different results, and qualitative reviews have failed to yield a consistent explanation for the results of the individual studies. This state of affairs suggests that the phenomenon may simply be too complex to be captured by individual studies varying 1 factor at a time and by reviews based on similar qualitative considerations. Therefore, the current investigation undertook a meta-analysis, a synthesis capturing the quantitative information across the now sizable number of studies. We entered several important factors into the meta-analysis, including the effects of age, the number of A trials, the length of delay between hiding and search, the number of locations, the distances between locations, and the distinctive visual properties of the hiding arrays. Of these, the analysis consistently indicated that age, delay, and number of hiding locations strongly influence infants' search. The pattern of specific findings also yielded new information about infant search. A general characterization of the results is that, at every age, both above-chance and below-chance performance was observed. That is, at each age at least 1 combination of delay and number of locations yielded above-chance A-not-B errors or significant perseverative search. At the same time, at each age at least 1 alternative combination of delay and number of locations yielded below-chance errors and significant above-chance correct performance, that is, significantly accurate search. These 2 findings, appropriately elaborated, allow us to evaluate all extant theories of stage 4 infant search. When this is done, all these extant accounts prove to be incorrect. That is, they are incommensurate with one aspect or another of the pooled findings in the meta-analysis. Therefore, we end by proposing a new account that is consistent with the entire data set.     

Are A-not-B errors caused by a belief about object location?

Eight- to 12-month-olds might make A-not-B errors, knowing the object is in B but searching at A because of ancillary (attention, inhibitory, or motor memory) deficits, or they might genuinely believe the object is in A (conceptual deficit). This study examined how diligently infants searched for a hidden object they never found. An object was placed in A twice, and then in B. In a different task the object was placed beside A twice, and then in B. Infants made more A-not-B errors in the former task, and perseverating infants searched diligently in A rather than in B. Infants seemed to believe the object was in A, suggesting that both a conceptual deficit and ancillary deficits account for A-not-B errors.     

Hindsight bias and developing theories of mind

Although hindsight bias (the "I knew it all along" phenomenon) has been documented in adults, its development has not been investigated. This is despite the fact that hindsight bias errors closely resemble the errors children make on theory of mind (ToM) tasks. Two main goals of the present work were to (a) create a battery of hindsight tasks for preschoolers, and (b) assess the relation between children's performance on these and ToM tasks. In two experiments involving 144 preschoolers, 3-, 4-, and 5-year olds exhibited strong hindsight bias. Performance on hindsight and ToM tasks was significantly correlated independent of age, language ability, and inhibitory control. These findings contribute to a more comprehensive account of perspective taking across the lifespan.     

Nearly 4 years after an event: children's eyewitness memory and adults' perceptions of children's accuracy

OBJECTIVE: The current study examined children's eyewitness memory nearly 4 years after an event and the ability of adults to evaluate such memory. METHOD: In Phase 1, 7- and 10-year olds were interviewed about a past event after a nearly 4-year delay. The interview included leading questions relevant to child abuse as well as statements designed to implicate the original confederate. In Phase 2, laypersons and professionals watched a videotaped interview (from Phase 1) that they were misled to believe was from an ongoing abuse investigation. Respondents then rated the child's accuracy and credibility, and the probability that the child had been abused. RESULTS: In Phase 1, few significant age differences in memory accuracy were found, perhaps owing in part to small sample size. Although children made a variety of commission errors, none claimed outright to have been abused. Nevertheless, some of the children's answers (e.g., saying that their picture had been taken, or that they had been in a bathtub) might cause concern in a forensic setting. In Phase 2, professional and nonprofessional respondents were unable to reliably estimate the overall accuracy of children's statements. However, respondents were able to reasonably estimate the accuracy of children's answers to abuse questions. Respondents were also more likely to think that 7-year olds compared to 10-year olds had been abused. Professionals were significantly less likely than nonprofessionals to believe that credible evidence of abuse existed. Professionals who indicated personal experience with child abuse or a close relationship with an abuse victim were more likely to rate children as abused. A gender bias to rate boys as more accurate than girls was apparent among laypersons but not professionals. CONCLUSIONS: Children were generally resistant to suggestions that abuse occurred during a long-ago generally forgotten event, but some potentially concerning errors were made. Both professionals and non-professionals had difficulty estimating the accuracy of children's reports, but adults were more likely to rate children as accurate if the children answered abuse-related questions correctly. Training and personal experience were associated with adults' ratings of children's reports. Implications for evaluations of child abuse reports are discussed.     

Very young children's memory for the location of objects in a large-scale environment

2 experiments were carried out to investigate 18- to 30-month-old children's memory for the location of a hidden object. In the first experiment, young children were observed in 2 different memory-for-location tasks, both conducted in their own homes. In 1, a toy was hidden in a natural location, and in the other it was hidden in one of a set of boxes with picture cues on top of them. Memory performance was significantly better when the toy was hidden within the natural environment. The effect of different types of hiding locations was examined further in the second experiment. No age differences were found when an object was hidden either in the natural environment or in 1 of a set of unmarked boxes (although performance was better in the former condition). However, in the third condition the older subjects (24-30 months) effectively used a landmark cue (a nearby piece of furniture) to help them remember in which plain box a toy had been hidden, but the young subjects (18-22 months) did not profit from such potential cues. The results, as well as some previous research with delayed-response tasks, were interpreted as reflecting developmental changes in very young children's ability to exploit available cues. The pattern of results suggested the possibility that 2-year-old children are capable of a simple form of mnemonic strategy, actively associating an available cue with the information to be remembered.     

盲童空间认知的参考框架和语言表达

采用旋转范式中的摸箭头和动物排列任务,考察盲童空间认知的参考框架和语言表达。结果表明,在空间认知中,盲童倾向使用相对参考框架和固定参考框架,倾向使用相对空间术语,也有小部分人使用绝对空间术语。盲童空间认知的参考框架和语言表达由盲童的特点决定。视觉经验和空间教育对盲童空间认知操作和空间语言表达有一定影响。     

The A-Not-B Error: Results from a Logistic Meta-Analysis

A meta-analysis of the A-not-B error was conducted using logistic regression on studies conducted before September 1997 (107 data points). An earlier meta-analysis by Wellman, Cross, and Bartsch revealed that age, delay between hiding and retrieval, and number of hiding locations were significant predictors of both the proportion of infants who searched correctly on B trials and the proportion of infants who searched perseveratively. The current analysis replicated these findings with two exceptions: (1) The number of trials at the A location was a significant predictor, and (2) the number of locations was a significant predictor of the proportion of infants who searched perseveratively, but not the proportion of infants who searched correctly. Implications of these findings are discussed and a quantitative version of a hierarchical competing-systems model of infant search is proposed.     

Children's eyewitness memory: effects of participation and forensic context.

We examined effects of participation and forensic context on 4-year-old children's testimony. Children in "participant" and "police" conditions actively participated in games with a "babysitter"; each child in the "observer" condition watched a videotape of a child and the babysitter playing. Eleven days later, children were individually questioned about the event. Before the interview began, children in the police condition talked to a police officer who said the babysitter might have done something bad. Comparison of participant- and observer-condition performance indicated that participation increased free-recall accuracy concerning actions that took place and lowered suggestibility. Comparison of participant- and police-condition performance indicated that forensic context led to increased error in free recall and additional comments to misleading questions. However, forensic context also resulted in higher accuracy on an age-identification task and did not affect children's accuracy in answering abuse-related questions.     

The Relations between Frontal Brain Electrical Activity and Cognitive Development during Infancy

The relations between changes in the scalp-recorded electroencephalogram (EEG) and the development of the ability to perform successfully 2 cognitive tasks attributed to frontal lobe functioning were examined in 13 infants from 7 to 12 months of age. Infants successful in performing the A-not-B task with increasingly longer delays across the second half of the first year of life showed changes in power in scalp-recorded brain electrical activity in the frontal region and an increase in anterior/posterior EEG coherence. Infants with rapid mastery of object retrieval did not differ in frontal EEG development from infants who exhibited the normal developmental progression in object retrieval performance. In a task examining inhibition of reaching to a novel toy, there were no differences in frontal EEG as a function of performance. Results from a cross-sectional sample revealed similar findings. These data confirm work with nonhuman primates on the importance of maturation of frontal cortex in the successful performance on certain tasks (A-not-B), but do not confirm nonhuman primate data on the importance of frontal cortex for other tasks (object retrieval). The data also suggest that the electroencephalogram may be useful as a noninvasive measure of central nervous system development during the first year of life.     

Children's use of frames of reference in communication of spatial location

The frames of reference used by 4-, 6-, and 8-year-old children were studied in a spatial direction-giving task. Children were asked to specify verbally the location of a toy hidden under one of several identical cups. The child and listener sat facing each other at opposite ends of a room that had distinctive or nondistinctive landmarks proximal and distal to the hiding location. Location needed to be specified with respect to either the left-right dimension, the front-back dimension, or both. The results indicated that (1) although children's overall performance improved with age, communication about the left-right dimension was particularly difficult for 4-year-old children and showed a higher rate of improvement with age than communication about the front-back dimension; and (2) the frames of reference that children incorporated into their directions changed with age and differed for directions about the front-back and left-right dimensions. Both 4- and 6-year-old children used person references (themselves or the listener) to specify front-back relations, but only the 6-year-olds were able to compensate for their apparent difficulty in using the terms left and right by using landmarks to specify the left-right dimension. Eight-year-olds used a combination of person and landmark references in directions about both dimensions. Discrepancies between the frames of reference children used to communicate spatial location and those typically used in other spatial cognition tasks are discussed in terms of developmental and task constraints.     

Putting the "Noun Bias" in Context: A Comparison of English and Mandarin

Recently, researchers have been debating whether children exhibit a universal "noun bias" when learning a first language. The present study compares the proportions of nouns and verbs in the early vocabularies of 24 English- and 24 Mandarin-speaking toddlers ( M age = 20 months) and their mothers. Three different methods were used to measure the proportion of noun types, relative to verb types: controlled observations in three contexts (book reading, mechanical toy play, regular toy play), identical across languages; a vocabulary checklist (MacArthur Communicative Development Inventory); and mothers' reporting of their children's "first words." Across all measures, Mandarin-speaking children were found to have relatively fewer nouns and more verbs than English-speaking children. However, context itself played an important role in the proportions of nouns found in children's vocabularies, such that, regardless of the language spoken, children's vocabularies appeared dominated by nouns when they were engaged in book reading, but not when they were playing with toys. Mothers' speech to children showed the same language differences (relatively more verbs in Mandarin), although both Mandarin- and English-speaking mothers produced relatively more verbs than their children. In sum, whether or not language-learning toddlers demonstrate a "noun bias" depends on a variety of factors, including the methods by which their vocabularies are sampled and the contexts in which observations occur.     

Predicting the outcomes of physical events: two-year-olds fail to reveal knowledge of solidity and support

Two-year-olds' (N = 153) knowledge of solidity was tested in four search tasks adapted from infant looking-time experiments. In Experiment 1, 2-year-olds failed to search in the correct location for a falling ball after a hidden shelf that blocked its trajectory had been inserted in the apparatus. Experiment 2 extended this finding by showing that 2-year-olds failed to take into account the effects of either removing or inserting a shelf in their search for a toy dropped behind a screen. Experiment 3 examined sensitivity to the constraint provided by a solid barrier on horizontal motion. In all three experiments, 2-year-old children searched initially at the location where they saw the object during familiarization. Experiment 4, using multiple test trials but no familiarization to a pretest location, also showed that 2-year-olds failed to take the presence or absence of a barrier into account when planning where to search for a toy they had seen dropped behind a screen. In all of these studies, 2-year-olds showed no evidence of representing solidity and support constraints on the trajectories of falling objects. Experiments 1 and 3 also included 2 1/2-year-olds (N = 31), who succeeded on these search tasks. The implications of the poor performance of 2-year-olds, in the face of success by very young infants on looking-time measures of sensitivity to similar constraints on object motion, are discussed.     

Developmental Differences in Decoding the Meanings of the Appraisal Actions of Teachers

Teachers convey evaluations through such "appraisal actions" as ability versus effort attributions for children's performance, spontaneous displays of warmth versus matter-of-fact acceptance, and attention versus inattention. Some appraisal actions (e.g., ability-effort) require an understanding of multiplicative relations to arrive at an "adult" interpretation. Others (e.g., attention-inattention) do not. First through sixth graders watched videotaped scenes in which teachers attributed one child's performance to ability but chided another for lack of effort even though he had given an equivalent performance, hugged one child but not another for equivalent performance, and paid attention to one child's oral report but not another's. Younger students (ages 5-9 to 7-10) rated the ability-attributed and hugged children as smarter; older students (ages 9-9 to 11-10) rated the effort-attributed and unhugged children as smarter. In contrast, no age differences were found in decoding attention versus inattention. The results suggest that younger children use a different strategy in decoding the meanings of complex appraisal actions.     

Acquiring Proper Nouns for Familiar and Unfamiliar Animate Objects: Two-Year-Olds' Word-learning Biases

In 2 studies, 2-year-old children learned a novel word modeled as a proper noun (e.g., "This is Zav") for an animate stuffed toy. Children who learned the word for a familiar object (i.e., one for which they knew a basic-level count noun for the kind) interpreted the word appropriately as a proper noun reliably more often than children who learned the word for an unfamiliar object (i.e., one for which they did not know such a count noun). When the creature was familiar, children typically interpreted the novel word as if it were a proper noun referring uniquely to the labeled individual. When the animal was unfamiliar, children frequently interpreted the word as if it were a count noun referring to a kind of object. Children's spontaneous comments during the tasks provided striking additional evidence that their interpretations of the proper noun varied with the familiarity of the object. The results suggest that young children's sensitivity to the form class of proper nouns is affected by the familiarity of the referent object. The findings are discussed in terms of interpretative biases in word learning.