Occlusions at event boundaries during encoding have a negative effect on infant memory

The present study investigated the importance of Event Boundaries for 16- and 20-month-olds’ (n = 80) memory for cartoons. The infants watched one out of two cartoons with ellipses inserted covering the screen for 3 s either at Event Boundaries or at Non-Boundaries. After a two-week delay both cartoons (one familiar and one novel) were presented simultaneously without ellipses while eye-tracking the infants. According to recent evidence a familiarity preference was expected. However, following Event Segmentation Theory ellipses at Event Boundaries were expected to cause greater disturbance of the encoding and hence a weaker memory trace evidenced by reduced familiarity preference, relative to ellipses at Non-Boundaries. The results suggest that overall this was the case, documenting the importance of Boundaries for infant memory. Furthermore, planned analyses revealed that whereas the same pattern was found when looking at the 20-month-old infants, no significant difference was found between the two conditions in the youngest age-group.     

Four‐month‐old infants individuate and track simple tools following functional demonstrations

Two experiments examined whether 4‐month‐olds (n = 120) who were induced to assign two objects to different categories would then be able to take advantage of these contrastive categorical encodings to individuate and track the objects. In each experiment, infants first watched functional demonstrations of two tools, a masher and tongs (Experiment 1) or a marker and a knife (Experiment 2). Next, half the infants saw the two tools brought out alternately from behind a screen, which was then lowered to reveal only one of the tools (different‐objects condition); the other infants saw similar events except that the same tool was shown on either side of the screen (same‐object condition). In both experiments, infants in the different‐objects condition looked reliably longer than those in the same‐object condition, and this effect was eliminated if the demonstrations involved similar but non‐functional actions. Together, these results indicate that infants (a) were led by the functional demonstrations they observed to assign the two tools to distinct categories, (b) recruited these categorical encodings to individuate and track the tools, and hence (c) detected a violation in the different‐objects condition when the screen was lowered to reveal only one tool. Categorical information thus plays a privileged role in individuation and identity tracking from a very young age.     

Object individuation in 10-month-old infants: Do significant objects make a difference?

Object individuation in 10-month-old infants is investigated in an experiment using a violation-of-expectation paradigm. Two variables are manipulated experimentally. The first variable is test condition (property/kind vs. spatiotemporal) analogous to the study by Xu and Carey [Cognitive Psychology 30 (1996) 111.]. The second variable is object type (novel vs. significant object). The results of the experiment show that test condition does make a difference, while object type does not. Further analysis shows the need to further investigate significant objects, which might confound the difference between familiar toys “preferred to play with” and familiar “comforting” toys.     

Delayed Match Retrieval: a novel anticipation‐based visual working memory paradigm

We tested 8‐ and 10‐month‐old infants’ visual working memory (VWM) for object‐location bindings – what is where – with a novel paradigm, Delayed Match Retrieval, that measured infants’ anticipatory gaze responses (using a Tobii T120 eye tracker). In an inversion of Delayed‐Match‐to‐Sample tasks and with inspiration from the game Memory, in test trials, three face‐down virtual ‘cards’ were presented. Two flipped over sequentially (revealing, e.g. a swirl pattern and then a star), and then flipped back face‐down. Next, the third card was flipped to reveal a match (e.g. a star) to one of the previously seen, now face‐down cards. If infants looked to the location where the (now face‐down) matching card had been shown, this was coded as a correct response. To encourage anticipatory looks, infants subsequently received a reward (a brief, engaging animation) presented at that location. Ten‐month‐old infants performed significantly above chance, showing that their VWM could hold object‐location information for the two cards. Overall, 8‐month‐olds’ performance was at chance, but they showed a robust learning trend. These results corroborate previous findings (Kaldy & Leslie, 2005; Oakes, Ross‐Sheehy & Luck, 2006) and point to rapid development of VWM for object‐location bindings. However, compared to previous paradigms that measure passive gaze responses to novelty, this paradigm presents a more challenging, ecologically relevant test of VWM, as it measures the ability to make online predictions and actively localize objects based on VWM. In addition, this paradigm can be readily scaled up to test toddlers or older children without significant modification.     

Choosing your informant: weighing familiarity and recent accuracy

In two experiments, children aged 3, 4 and 5 years (N= 61) were given conflicting information about the names and functions of novel objects by two informants, one a familiar teacher, the other an unfamiliar teacher. On pre‐test trials, all three age groups invested more trust in the familiar teacher. They preferred to ask for information and to endorse the information that she supplied. In a subsequent phase, children watched as the two teachers differed in the accuracy with which they named a set of familiar objects. Half the children saw the familiar teacher name the objects accurately and the unfamiliar teacher name them inaccurately. The remaining half saw the reverse arrangement. In post‐test trials, the selective trust initially displayed by 3‐year‐olds was minimally affected by this intervening experience of differential accuracy. By contrast, the selective trust of 4‐ and 5‐year‐olds was affected. If the familiar teacher had been the more accurate, selective trust in her was intensified. If, on the other hand, the familiar teacher had been the less accurate, it was undermined, particularly among 5‐year‐olds. Thus, by 4 years of age, children trust familiar informants but moderate that trust depending on the informants’ recent history of accuracy or inaccuracy.     

Novel labels support 10-month-olds’ attention to novel objects

What is the source of the mutual exclusivity bias whereby infants map novel labels onto novel objects? In an intermodal preferential looking task, we found that novel labels support 10-month-olds’ attention to a novel object over a familiar object. In contrast, familiar labels and a neutral phrase gradually reduced attention to a novel object. Markman (1989, 1990) argued that infants must recall the name of a familiar object to exclude it as the referent of a novel label. We argue that 10-month-olds’ attention is guided by the novelty of objects and labels rather than knowledge of the names for familiar objects. Mutual exclusivity, as a language-specific bias, might emerge from a more general constraint on attention and learning.     

Do 6‐month‐olds understand that speech can communicate?

Adults and 12‐month‐old infants recognize that even unfamiliar speech can communicate information between third parties, suggesting that they can separate the communicative function of speech from its lexical content. But do infants recognize that speech can communicate due to their experience understanding and producing language, or do they appreciate that speech is communicative earlier, with little such experience? We examined whether 6‐month‐olds recognize that speech can communicate information about an object. Infants watched a Communicator selectively grasp one of two objects (target). During test, the Communicator could no longer reach the objects; she turned to a Recipient and produced speech (a nonsense word) or non‐speech (coughing). Infants looked longer when the Recipient selected the non‐target than the target object when the Communicator spoke but not when she coughed – unless the Recipient had previously witnessed the Communicator's selective grasping of the target object. Our results suggest that at 6 months, with a receptive vocabulary of no more than a handful of commonly used words, infants possess some abstract understanding of the communicative function of speech. This understanding may provide an early mechanism for language and knowledge acquisition.     

Infant categorization of containment,support and tight‐fit spatial relationships

Two experiments examined infant categorization of containment, support or tight‐fit spatial relationships. English‐learning infants of 10 months (Experiment 1) and 18 months (Experiment 2) were habituated to four pairs of objects in one of these relationships. They were then tested with one event from habituation, one with novel objects in the familiar relationship, one with familiar objects in a novel relationship and one with novel objects in a novel relationship. Infants at both ages generalized their habituation of the containment relationship to novel objects in this relationship. In the support and tight‐fit conditions, the younger infants responded only to the novel objects in the test while the older infants responded to the novel relationship, but only with familiar objects. The results indicate that infants learn to categorize containment prior to support or tight‐fit relationships and suggest that infants can recognize a relationship between familiar objects prior to novel objects.     

Infants’ sensitivity to familiar size: The effect of memory on spatial perception

Two experiments investigated infants’ sensitivity to familiar size as information for the distances of objects with which they had had only brief experience. Each experiment had two phases: a familiarization phase and a test phase. During the familiarization phase, the infant played with a pair of different-sized objects for 10 min. During the test phase, a pair of objects, identical to those seen in the familiarization phase but now equal in size, were presented to the infant at a fixed distance under monocular or binocular viewing conditions. In the test phase of Experiment 1, 7-month-old infants viewing the objects monocularly showed a significant preference to reach for the object that resembled the smaller object in the familiarization phase. Seven-month-old infants in the binocular viewing condition reached equally to the two test phase objects. These results indicate that, in the monocular condition, the 7-month-olds used knowledge about the objects’ sizes, acquired during the familiarization phase, to perceive distance from the test objects’ visual angles, and that they reached preferentially for the apparently nearer object. The lack of a reaching preference in the binocular condition rules out interpretations of the results not based on the objects’ perceived distances. The results, therefore, indicate that 7-month-old infants can use memory to mediate spatial perception. The implications of this finding for the debate between direct and indirect theories of visual perception are discussed. In the test phase of Experiment 2,5-month-old infants viewing the objects monocularly showed no reaching preference. These infants, therefore, showed no evidence of sensitivity to familiar size as distance information.     

Recognizing the role of perception in action at 6 months

The present research examined whether infants as young as 6 months of age would consider what objects a human agent could perceive when interpreting her actions on the objects. In two experiments, the infants took the agent's actions of repeatedly reaching for and grasping one of two possible objects as suggesting her preference for that object only when the agent could detect both objects, not when the agent's perceptual access to the second object was absent, either because a large screen hid the object from the agent ( Experiment 1 ), or because the agent sat with her back toward the object ( Experiment 2 ). These results suggest that young infants recognize the role of perception in constraining an agent's goal‐actions.     

The reliability of a model influences 14-month-olds’ imitation

Human infants have an enormous amount to learn from others to become full-fledged members of their culture. Thus, it is important that they learn from reliable, rather than unreliable, models. In two experiments, we investigated whether 14-month-olds (a) imitate instrumental actions and (b) adopt the individual preferences of a model differently depending on the model’s previous reliability. Infants were shown a series of videos in which a model acted on familiar objects either competently or incompetently. They then watched as the same model demonstrated a novel action on an object (imitation task) and preferentially chose one of two novel objects (preference task). Infants’ imitation of the novel action was influenced by the model’s previous reliability; they copied the action more often when the model had been reliable. However, their preference for one of the novel objects was not influenced by the model’s previous reliability. We conclude that already by 14 months of age, infants discriminate between reliable and unreliable models when learning novel actions.     

Fourteen-month-olds’ imitation is influenced more strongly by a model’s competence than by a model’s certainty

Research has shown that infants are more likely to learn from certain and competent models than from uncertain and incompetent models. However, it is unknown which of these cues to a model’s reliability infants consider more important. In Experiment 1, we investigated whether 14-month-old infants (n = 35) imitate and adopt tool choices selectively from an uncertain but competent compared to a certain but incompetent model. Infants watched videos in which an adult expressed either uncertainty but acted competently or expressed certainty but acted incompetently with familiar objects. In tool-choice tasks, the adult then chose one of two objects to operate an apparatus, and in imitation tasks, the adult then demonstrated a novel action. Infants did not adopt the model’s choice in the tool-choice tasks but they imitated the uncertain but competent model more often than the certain but incompetent model in the imitation tasks. In Experiment 2, 14-month-olds (n = 33) watched videos in which an adult expressed only either certainty or uncertainty in order to test whether infants at this age are sensitive to a model’s certainty. Infants imitated and adopted the tool choice from a certain model more than from an uncertain model. These results suggest that 14-month-olds acknowledge both a model’s competence and certainty when learning novel actions. However, they rely more on a model’s competence than on his certainty when both cues are in conflict. The ability to detect reliable models when learning how to handle cultural artifacts helps infants to become well-integrated members of their culture.     

Gaze,goals and growing up: Effects on imitative grasping

Developmental differences in the use of social‐attention cues to imitation were examined among children aged 3 and 6 years old (n = 58) and adults (n = 29). In each of 20 trials, participants watched a model grasp two objects simultaneously and move them together. On every trial, the model directed her gaze towards only one of the objects. Some object pairs were related and had a clear functional relationship (e.g., flower, vase), while others were functionally unrelated (e.g., cardboard square, ladybug). Owing to attentional effects of eye gaze, it was expected that all participants would more faithfully imitate the grasp on the gazed‐at object than the object not gazed‐at. Children were expected to imitate less faithfully on trials with functionally related objects than those without, due to goal‐hierarchy effects. Results support effects of eye gaze on imitation of grasping. Children's grasping accuracy on functionally related and functionally unrelated trials was similar, but they were more likely to only use one hand on trials where the object pairs were functionally related than unrelated. Implications for theories of imitation are discussed.     

Retrieval-induced forgetting in rats

“Retrieval-induced forgetting” in rats was evaluated using a modified spontaneous object recognition test. The test consisted of a sample phase, retrieval or interference phase, and a test phase with 60-min delay period inserted between the phases. Rats were randomly assigned to one of three groups (control, retrieval and interference) and allowed to explore the field in which two different objects (A, B) were placed in the sample phase. In the retrieval phase, two identical objects (B, B), which were the same as one of the objects presented in the sample phase, were placed again. In the interference phase, two identical objects (C, C), which were novel for animals, were placed. In the test phase, two different objects (A, D), one of which was identical to that presented in sample phase (familiar object) and the other was novel, were placed and the time spent exploring each object was analyzed. While the exploration of the novel object was significantly longer than that of the familiar object in rats subjected to the interference phase, rats subjected to the retrieval phase could not discriminate between the familiar and the novel objects at the test phase. These results demonstrate the “retrieval-induced forgetting” phenomenon in a spontaneous object recognition test in rats.     

Reasoning about collisions involving inert objects in 7.5‐month‐old infants

The present research asked whether 7.5‐month‐old infants realize that an object cannot displace another object without contacting it. The infants in Experiment 1 were assigned to a contact or a no‐contact condition. The infants in the no‐contact condition saw static familiarization displays in which a tall, thin barrier stood across the bottom of a ramp; a cylinder rested against the left side of the barrier and a wheeled toy bug against its right side. The infants in the contact condition saw similar displays except that a large portion of the barrier’s lower half was removed so that the cylinder rested directly against the bug. Next, a small screen was placed in front of the bottom of the ramp; only the upper portion of the barrier was visible above the screen. The infants in the two conditions watched the same test event. The cylinder was released and rolled to the bottom of the ramp, partly disappearing behind the screen’s left edge; next, the bug rolled down the track, as though launched by the cylinder. The infants in the no‐contact condition looked reliably longer at the test event than did those in the contact condition. This result suggested that the infants (a) viewed the bug as an inert object that could move only when acted upon; (b) believed that the cylinder could not act on the bug without contacting it; (c) realized that the cylinder could contact the bug when the half‐barrier but not the barrier was present; (d) remembered after the screen was raised whether contact was possible between the cylinder and bug; and (e) were surprised in the no‐contact condition when the bug was launched down the track. A second experiment confirmed the results of Experiment 1. Previous research comparing infants’ responses to no‐contact and contact events has typically made use of self‐moving rather than inert objects. These experiments have consistently found that infants do not look reliably longer at no‐contact than at contact events. In the General Discussion, we examine the contrast between these prior results and the present results and speculate on how infants’ expectations about inert and self‐moving objects may be best characterized.     

Relational memory during infancy: evidence from eye tracking

Here we report evidence from a new eye‐tracking measure of relational memory that suggests that 9‐month‐old infants can encode memories in terms of the relations among items, a function putatively subserved by the hippocampus. Infants learned about the association between faces that were superimposed on unique scenic backgrounds. During test trials, infants were shown three faces presented on a familiar scene. All three faces were equally familiar; however, one had been presented with the test background earlier. Visual behavior was recorded continuously using a TOBII eye tracker. Infants looked preferentially at the face that matched the test background very early in the trial; however, the time course of this preferential looking effect varied as a function of delay. These results suggest that by 9 months of age infants can form memories that represent the relations among items and maintain them over short delays.     

Modeling recall memory for emotional objects in Alzheimer's disease

ABSTRACT

Objective: To examine whether emotional memory (EM) of objects with self-reference in Alzheimer's disease (AD) can be modeled with binomial logistic regression in a free recall and an object recognition test to predict EM enhancement.?Method: Twenty patients with AD and twenty healthy controls were studied. Six objects (three presented as gifts) were shown to each participant. Ten minutes later, a free recall and a recognition test were applied. The recognition test had target–objects mixed with six similar distracter objects. Participants were asked to name any object in the recall test and identify each object in the recognition test as known or unknown.?Results: The total of gift objects recalled in AD patients (41.6%) was larger than neutral objects (13.3%) and a significant EM recall effect for gifts was found (Wilcoxon: p < .003). EM was not found for recognition in AD patients due to a ceiling effect. Healthy older adults scored overall higher in recall and recognition but showed no EM enhancement due to a ceiling effect. A logistic regression showed that likelihood of emotional recall memory can be modeled as a function of MMSE score (p < .014) and object status (p < .0001) as gift or non-gift.?Conclusion: Recall memory was enhanced in AD patients for emotional objects indicating that EM in mild to moderate AD although impaired can be provoked with strong emotional load. The logistic regression model suggests that EM declines with the progression of AD rather than disrupts and may be a useful tool for evaluating magnitude of emotional load.     

Why does visual working memory ability improve with age: More objects,more feature detail,or both? A registered report

We investigated how visual working memory (WM) develops with age across the early elementary school period (6–7 years), early adolescence (11–13 years), and early adulthood (18–25 years). The work focuses on changes in two parameters: the number of objects retained at least in part, and the amount of feature-detail remembered for such objects. Some evidence suggests that, while infants can remember up to three objects, much like adults, young children only remember around two objects. This curious, nonmonotonic trajectory might be explained by differences in the level of feature-detail required for successful performance in infant versus child/adult memory paradigms. Here, we examined if changes in one of two parameters (the number of objects, and the amount of detail retained for each object) or both of them together can explain the development of visual WM ability as children grow older. To test it, we varied the amount of feature-detail participants need to retain. In the baseline condition, participants saw an array of objects and simply were to indicate whether an object was present in a probed location or not. This phase begun with a titration procedure to adjust each individual's array size to yield about 80% correct. In other conditions, we tested memory of not only location but also additional features of the objects (color, and sometimes also orientation). Our results suggest that capacity growth across ages is expressed by both improved location-memory (whether there was an object in a location) and feature completeness of object representations.     

Location of a missing object and detection of its absence by infants: Contribution of an eye‐tracking system to the understanding of infants' strategies

Previous research has demonstrated infants' capacity to discriminate between situations in which all the objects successively hidden behind a screen are present, or not, after the removal of the screen. Two types of interpretation have been proposed: counting capacity or object memorization capacity. In the usual paradigm, the missing object in the impossible event is usually the last object which is placed behind the screen. Following this, a third interpretation can be offered: infants' exploration is first directed to this object's location, and its presence or absence is noticed. Two experiments using Wynn's (Nature 1992; 358 :749) paradigm were performed to test the third hypothesis. The first experiment involved four objects (teddy bears) placed in four squares. Infants looked longer at the impossible event (3 objects, the last one missing) than at the possible event (4 objects) when the impossible event was presented first. No difference in looking duration was observed for the opposite order. In the second experiment, the four objects were disposed in a line and an eye‐tracking system was used. No difference in the number of looks was observed between the impossible event (3 objects, the second one missing) and the possible event (4 objects). Therefore, it appears that at least in this complex situation (4 objects used instead of 2 usually), the location of the missing object is a key factor for event discrimination. Eye‐tracking also indicated in the second experiment that infants looked less at the second location during an impossible event (object missing) than during the possible event (object present), indicating that the impossibility of the event was not a determining factor for looking durations. Altogether, the data indicate the potential usefulness of eye‐tracking analysis in this type of situation. Copyright © 2004 John Wiley & Sons, Ltd.