Age-related changes in deferred imitation from television by 6- to 18-month-olds

During the second year of life, infants exhibit a video deficit effect. That is, they learn significantly less from a televised demonstration than they learn from a live demonstration. We predicted that repeated exposure to televised demonstrations would increase imitation from television, thereby reducing the video deficit effect. Independent groups of 6- to 18-month-olds were exposed to live or videotaped demonstrations of target actions. Imitation of the target actions was measured 24 hours later. The video segment duration was twice that of the live presentation. Doubling exposure ameliorated the video deficit effect for 12-month-olds but not for 15- and 18-month-olds. The 6-month-olds imitated from television but did not demonstrate a video deficit effect at all, learning equally well from a live and video demonstration. Findings are discussed in terms of the perceptual impoverishment theory and the dual representation theory.     

Adding odor: Less distress and enhanced attention for 6-month-olds

The effect of odor on cognitive and emotional processes has been studied in adults and children, but less so in infants. In this study twenty-seven six-month-olds were presented with a video while in either an odor (pine or baby-powder) or a no odor control condition. The video was a 92-s audiovisual presentation of a woman expressing happiness and sadness, with the order of emotion counterbalanced. Infant attention (looking time) and emotional expression (smiling, crying, mouthing) were coded. Infants looked longer in the presence of odor and expressed less crying and mouthing but more smiling behavior. Presence of odor markedly reduced infant emotional distress and increased attention, suggesting that the olfactory sensory system provides cues to infants that support mood regulation and maintain attention. These results have implications for optimizing infant environments for emotional health and cognitive development.     

Perception and production of object-related grasping in 6-month-olds

In this study, 6-month-olds’ perception of an object-related human grasping action was compared with their level of grasping performance using a within-participants design. In the action perception task, infants were presented with the video of an actor’s grasping movement toward an occluded target object. Subsequently, an expected and an unexpected final state of this grasping movement were presented simultaneously, and infants’ looking times were measured. In the action production task, infants were presented with three graspable objects. Infants’ grasping behavior was coded to be either palmar or thumb-opposite grasping. Results indicate that infants who were already able to perform a thumb-opposite grasp differentiated between the two final states in the action perception task by looking longer toward the unexpected final state. In contrast, infants who showed only palmar grasps looked equally long toward both final states. This finding supports the assumption that action perception and action control are already closely related in infants as young as 6 months.     

Deferred imitation in 18-month-olds from two cultural contexts: The case of Cameroonian Nso farmer and German-middle class infants

Imitative learning has been described in naturalistic studies for different cultures, but lab-based research studying imitative learning across different cultural contexts is almost missing. Therefore, imitative learning was assessed with 18-month-old German middle-class and Cameroonian Nso farmer infants – representing two highly different eco-cultural contexts associated with different cultural models, the psychological autonomy and the hierarchical relatedness – by using the deferred imitation paradigm. Study 1 revealed that the infants from both cultural contexts performed a higher number of target actions in the deferred imitation than in the baseline phase. Moreover, it was found that German middle-class infants showed a higher mean imitation rate as they performed more target actions in the deferred imitation phase compared with Cameroonian Nso farmer infants. It was speculated that the opportunity to manipulate the test objects directly after the demonstration of the target actions could enhance the mean deferred imitation rate of the Cameroonian Nso farmer infants which was confirmed in Study 2. Possible explanations for the differences in the amount of imitated target actions of German middle-class and Cameroonian Nso farmer infants are discussed considering the object-related, dyadic setting of the imitation paradigm with respect to the different learning contexts underlying the different cultural models of learning.     

On perception of a partially occluded object in 6-month-olds

An Event Set x Event Set design used the occluded stick, solid stick, and divided stick stimulus events from Experiment 1 by Kellman and Spelke (1983). The design was analyzed using five different psychological models of the additive components of infant looking time in the nine cells of the design. Application of linear regression analysis to the data revealed that four of the models fit well. The best fitting model was shown to have two possible psychological interpretations. In one interpretation the infants represent the occluded stick as a solid stick but in the other the infants look longer in response to changes involving the divided stick. The fit of this model was greatly improved by assuming that some of the infants prefer looking at the novel stimulus but others prefer looking at the familiar stimulus. The implications of familiarity preference for the conduct and interpretation of other research are discussed.     

Reconsolidation after remembering an odor-reward association requires NMDA receptors

A rapidly learned odor discrimination task based on spontaneous foraging behavior of the rat was used to evaluate the role of N-methyl-D-aspartate (NMDA) receptors (NMDARs) in ongoing memory consolidation. Rats were trained in a single session to discriminate among three odors, one of which was associated with palatable food reward. Previous experiments showed that the NMDAR antagonist DL-APV induced amnesia for this task when injected immediately after training. In the present study, memory was reactivated 24 h after training by exposure to the rewarded odor within the experimental context after which rats received an intracerebroventricular injection of APV. Combined reactivation-drug treatment induced profound amnesia when tested 48 h later. Animals receiving drug alone, in absence of reactivation, showed perfect retention. It is concluded that NMDARs support a consolidation process taking place after memory reactivation.     

A demonstration of gaze following in 3- to 6-month-olds

An adult, with a puppet held at shoulder height on either side (within the infant's visual field), interacted with 3- to-6-month-olds, turning her head intermittently to talk to a puppet. Seventy- three percent of infants' first eye-turns were in the direction of the adult head-turn.     

Cross-language word segmentation by 9-month-olds

Dutch-learning and English-learning 9-month-olds were tested, using the Headturn Preference Procedure, for their ability to segment Dutch words with strong/weak stress patterns from fluent Dutch speech. This prosodic pattern is highly typical for words of both languages. The infants were familiarized with pairs of words and then tested on four passages, two that included the familiarized words and two that did not. Both the Dutch- and the English-learning infants gave evidence of segmenting the targets from the passages, to an equivalent degree. Thus, English-learning infants are able to extract words from fluent speech in a language that is phonetically different from English. We discuss the possibility that this cross-language segmentation ability is aided by the similarity of the typical rhythmic structure of Dutch and English words.     

Attribution of dispositional states by 12-month-olds

The ability to interpret the behavior of other individuals is essential for effective social functioning. Many investigators now believe that even young infants can recognize that agents act toward goals. Here we report three experiments suggesting that 12-month-old infants not only can recognize goal-related action, but also can interpret future actions of an actor on the basis of previously witnessed behavior in another context. The possibility that this inference is made through the attribution of mental states is discussed.     

Form categorization in 10-month-olds

In five experiments, 10-month-olds were habituated to exemplars of a form category and tested for categorization in paired-comparison trials involving in-category versus out-of-category stimuli. Across these experiments, color was systematically manipulated during habituation and/or test trials. Infants categorized form when color was either held constant or varied during habituation, but failed to categorize form when exposed to color-constant stimuli during habituation and tested for categorization with novel-color form exemplars. Two subsequent experiments traced this failure to the narrow experience of exposure to color-constant exemplars during habituation. These results suggest that (a) infants' internal representation for a category will not include a stimulus dimension not varied in the exemplars from which the category was derived, but (b) if variation in that dimension is experienced, exemplars constructed of novel instances of that dimension will still be regarded as belonging to the category.     

Intention-based evaluations of distributive actions by 4-month-olds

Four-month-olds’ ability to consider the intentions of agents performing distributive actions was investigated in four experiments, using the Violation of Expectation paradigm (VoE) (Experiments 1–3) and the Preferential Looking paradigm (Experiment 4). In Experiment 1, infants were presented with two events showing two types of failed attempts to perform a distribution. In an attempt to distribute fairly, the distributor first tried to reach one of the recipients to deliver an apple, he failed, and then attempted to reach the other recipient to deliver a second apple and also failed. In an attempt to distribute unfairly, a different distributor tried unsuccessfully to bring resources always to the same recipient. Infants looked reliably longer at failed fair distribution events, suggesting that they did not just react to the actions outcomes and they attended to agents' intentions. Experiments 2 and 3 assessed alternative explanations based on perceptual factors or affiliative behaviors. In Experiment 4, during the test trials, infants were shown both distributors simultaneously and they preferred to look at the fair rather than at the unfair distributor. Overall, these findings reveal an early ability to take into account distributors’ intentions and a preference for watching agents that tried to distribute resources fairly.     

Memory retrieval by 18--30-month-olds: age-related changes in representational flexibility

Deferred imitation was used to trace changes in memory retrieval by 18-30-month-olds. In all experiments, an adult demonstrated 2 sets of actions using 2 different sets of stimuli. In Experiments 1A and 1B, independent groups of infants were tested immediately or after a 24-hr delay. Each infant was tested with 1 set of stimuli from the original demonstration and 1 set of stimuli that was different. Recall of the target actions when tested with different stimuli increased as a function of age, particularly after a delay. In Experiment 2, infants were provided with a unique verbal label for the stimuli during the demonstration and the test. The verbal label facilitated performance by 24-month-olds tested with different stimuli but had no effect on performance by 18-month-olds. One hallmark of memory development appears to be an age-related increase in the range of effective retrieval cues for a particular memory.     

Operational momentum in large-number addition and subtraction by 9-month-olds

Recent studies on nonsymbolic arithmetic have illustrated that under conditions that prevent exact calculation, adults display a systematic tendency to overestimate the answers to addition problems and underestimate the answers to subtraction problems. It has been suggested that this operational momentum results from exposure to a culture-specific practice of representing numbers spatially; alternatively, the mind may represent numbers in spatial terms from early in development. In the current study, we asked whether operational momentum is present during infancy, prior to exposure to culture-specific representations of numbers. Infants (9-month-olds) were shown videos of events involving the addition or subtraction of objects with three different types of outcomes: numerically correct, too large, and too small. Infants looked significantly longer only at those incorrect outcomes that violated the momentum of the arithmetic operation (i.e., at too-large outcomes in subtraction events and too-small outcomes in addition events). The presence of operational momentum during infancy indicates developmental continuity in the underlying mechanisms used when operating over numerical representations.     

Multimodal events and moving locations: eye movements of adults and 6-month-olds reveal dynamic spatial indexing

The ability to keep track of locations in a dynamic, multimodal environment is crucial for successful interactions with other people and objects. The authors investigated the existence and flexibility of spatial indexing in adults and 6-month-old infants by adapting an eye-tracking paradigm from D. C. Richardson and M. J. Spivey (2000). Multimodal events were presented in specific locations, and eye movements were measured when the auditory portion of the stimulus was presented without its visual counterpart. Experiment 1 showed that adults spatially index auditory information even when the original associated locations move. Experiments 2 and 3 showed that infants are capable of both binding multimodal events to locations and tracking those locations when they move.     

Words (but not tones) facilitate object categorization: evidence from 6- and 12-month-olds

Recent studies reveal that naming has powerful conceptual consequences within the first year of life. Naming distinct objects with the same word highlights commonalities among the objects and promotes object categorization. In the present experiment, we pursued the origin of this link by examining the influence of words and tones on object categorization in infants at 6 and 12 months. At both ages, infants hearing a novel word for a set of distinct objects successfully formed object categories; those hearing a sequence of tones for the same objects did not. These results support the view that infants are sensitive to powerful and increasingly nuanced links between linguistic and conceptual units very early in the process of lexical acquisition.     

Infant timekeeping: attention and temporal estimation in 4-month-olds

Four–month–old infants were exposed to sequences in which a 2–s light stimulus alternated with dark interstimulus periods whose length was manipulated to be 3 or 5 s. A predictable on–off pattern occurred for eight trials, but the light stimulus was omitted on the ninth trial. Infants showed heart rate responses on the omission trial that were closely synchronized with the expected recurrence of the stimulus. In addition, these heart rate patterns were observed predominantly in infants who had previously shown high levels of sustained attention in pretests with visual stimuli. These findings indicate remarkable precision in infants' estimation of time intervals, and suggest that the link between time estimation and attentional processes is present in early infancy.     

Situated robotics: from learning to teaching by imitation

This paper presents an approach to imitation learning in robotics focusing on low level behaviours, so that they do not need to be encoded into sets and rules, but learnt in an intuitive way. Its main novelty is that, rather than trying to analyse natural human actions and adapting them to robot kinematics, humans adapt themselves to the robot via a proper interface to make it perform the desired action. As an example, we present a successful experiment to learn a purely reactive navigation behaviour using robotic platforms. Using Case Based Reasoning, the platform learns from a human driver how to behave in the presence of obstacles, so that no kinematics studies or explicit rules are required.     

Islands of memory: Autobiographical remembering in amnestics

In amnestics with anterograde amnesia, memories of post-onset autobiographical experiences, if present at all, are typically barren and impoverished. However, there have been sporadic reports of islands of memory—memories that are vivid, detailed, and specific to time and place. The aim of this study was to verify the presence of such memories and examine their incidence rate. Anterograde amnestics were interviewed in their home using a narrative interviewing strategy with a view to describing memory in everyday life. Each autobiographical memory of a post-onset event was coded for quantity-length, and quality-episodicity. In just over half of the amnestics (8 out of 14), a memory that was lengthy, rich in personal details, and localisable was recollected. The quantitative and qualitative aspects of these island memories were significantly different from the other autobiographical memories that the amnestics supplied. These memories were at odds with what would be expected on the basis of their performance on standardised memory instruments. Our findings suggest there is occasionally more variability in remembering of autobiographical experiences in some amnestics than has traditionally been believed.