Number discrimination in 10‐month‐old infants

Two experiments investigated developmental changes in large number discrimination with visual‐spatial arrays. Previous studies found that 6‐month‐old infants were able to discriminate arrays that differ by a ratio of 1:2 but not 2:3. We found that by 10 months, infants were able to reliably discriminate 8 from 12 elements (2:3) but not 8 from 10 elements (4:5). Thus, number discrimination improves in precision during the first year, and these findings converge with studies using auditory stimuli.     

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.     

Linking actions and emotions: Evidence from 15‐ and 18‐month‐old infants

This study investigated 15‐ and 18‐month‐olds' understanding of the link between actions and emotions. Infants watched a videotape in which three adult models performed an action on an object. Each adult expressed the same emotion (positive, negative, or neutral affect) on completion of the action. Infants were subsequently given 20 seconds to interact with the object. Infants were less likely to perform the target action after the models' expressed negative as opposed to positive or neutral affect. Although infants' imitative behaviour was influenced by the models' emotional displays, this social referencing effect was not apparent in their more general object‐directed behaviour. For instance, infants in the negative emotion condition were just as quick to touch the object and spent the same amount of time touching the object as did infants in the neutral and positive emotion conditions. These findings suggest that infants understood that the models' negative affect was in response to the action, rather than the object itself. Infants apparently used this negative emotional information to appraise the action as one that was ‘undesirable’ or ‘bad’. Consequently, infants were now loath to reproduce the action themselves.     

Neural markers of subordinate‐level categorization in 6‐ to 7‐month‐old infants

Subordinate‐level category‐learning processes in infants were investigated with ERP and looking‐time measures. ERPs were recorded while 6‐ to 7‐month‐olds were presented with Saint Bernard images during familiarization, followed by novel Saint Bernards interspersed with Beagles during test. In addition, infant looking times were measured during a paired‐preference test (novel Saint Bernard vs. novel Beagle) conducted at the conclusion of ERP recording. Slow wave activity corresponded with learning a familiarized category at the subordinate and basic levels, whereas Negative central (Nc) and P400 components were linked with novel category preference. The results provide the first evidence identifying the neural markers of subordinate‐level categorization observed in looking‐time tasks conducted with infants. Moreover, when considered in conjunction with prior research investigating the neural markers of basic‐level categorization in infants, the findings indicate that (1) slow wave and Nc components of infant ERP waveforms are general markers for processes of category learning on the one hand and novel category preference on the other, (2) novel category preference for a contrast category at the basic and subordinate levels have the Nc component in common, but novel category preference at the subordinate level is accompanied by an additional P400 component, a finding in keeping with the notion that subordinate‐level categorization is governed by mechanisms supplementary to those underlying basic‐level categorization, and (3) slow wave activity associated with subordinate‐level learning followed that associated with basic‐level learning by approximately 200 ms, a result in accord with a coarse‐to‐fine scheme for the emergence of category partitioning.     

Electrophysiological responses to auditory novelty in temperamentally different 9‐month‐old infants

Behavioral reactivity to novel stimuli in the first half‐year of life has been identified as a key aspect of early temperament and a significant precursor of approach and withdrawal tendencies to novelty in later infancy and early childhood. The current study examines the neural signatures of reactivity to novel auditory stimuli in 9‐month‐old infants in relation to prior temperamental reactivity. On the basis of the assessment of behavioral reactivity scores at 4 months of age, infants were classified into groups of high negatively reactive and high positively reactive infants. Along with an unselected control group, these groups of temperamentally different infants were given a three‐stimulus auditory oddball task at 9 months of age which employed frequent standard and infrequent deviant tones as well as a set of complex novel sounds. In comparison to high positively reactive and control infants, high negatively reactive infants displayed increased amplitude of a positive slow wave in the ERP response to deviant tones compared to standard tones. In contrast, high positively reactive infants showed a larger novelty P3 to the complex novel sounds. Results are discussed in terms of optimal levels of novelty for temperamentally different infants.     

Repeated reminders inrease the speed of memory retrieval by 3‐month‐old infants

In two experiments, we examined the effect of repeated reminder treatments on the speed of memory retrieval by 3‐month‐old human infants. Infants were trained for two consecutive days to kick their feet to produce movement in an overhead mobile. Infants in the one‐reminder condition received a 3 min reminder treatment 13 days after the conclusion of training. Infants in the two‐reminder condition received one 3 min reminder treatment 6 days after the conclusion of training and a second reminder treatment 7 days later (i.e. 13 days following the conclusion of training). Infants in the no‐reminder control condition were not exposed to the reminder prior to the long‐term retention test. In the absence of a reminder treatment, infants exhibited complete forgetting during the long‐term test. Infants exposed to one reminder exhibited retention when tested 24 h after their only reminder, but not when tested earlier. Infants exposed to two reminder treatments, on the other hand, exhibited retention when tested 1, 4 or 24 h after their second reminder treatment. We conclude that the opportunity to retrieve the memory on a prior occasion facilitated subsequent memory retrieval.     

Fourteen‐month‐old infants learn similar‐sounding words

Can infants, in the very first stages of word learning, use their perceptual sensitivity to the phonetics of speech while learning words? Research to date suggests that infants of 14 months cannot learn two similar‐sounding words unless there is substantial contextual support. The current experiment advances our understanding of this failure by testing whether the source of infants’ difficulty lies in the learning or testing phase. Infants were taught to associate two similar‐sounding words with two different objects, and tested using a visual choice method rather than the standard Switch task. The results reveal that 14‐month‐olds are capable of learning and mapping two similar‐sounding labels; they can apply phonetic detail in new words. The findings are discussed in relation to infants’ concurrent failure, and the developmental transition to success, in the Switch task.     

Language‐specific stress perception by 9‐month‐old French and Spanish infants

During the first year of life, infants begin to have difficulties perceiving non‐native vowel and consonant contrasts, thus adapting their perception to the phonetic categories of the target language. In this paper, we examine the perception of a non‐segmental feature, i.e. stress. Previous research with adults has shown that speakers of French (a language with fixed stress) have great difficulties in perceiving stress contrasts ( Dupoux, Pallier, Sebastián & Mehler, 1997 ), whereas speakers of Spanish (a language with lexically contrastive stress) perceive these contrasts as accurately as segmental contrasts. We show that language‐specific differences in the perception of stress likewise arise during the first year of life. Specifically, 9‐month‐old Spanish infants successfully distinguish between stress‐initial and stress‐final pseudo‐words, while French infants of this age show no sign of discrimination. In a second experiment using multiple tokens of a single pseudo‐word, French infants of the same age successfully discriminate between the two stress patterns, showing that they are able to perceive the acoustic correlates of stress. Their failure to discriminate stress patterns in the first experiment thus reflects an inability to process stress at an abstract, phonological level.     

Seven‐ to 9‐month‐old infants use facial expressions to interpret others' actions

In Study 1, 7‐month‐old infants (N = 58) looked reliably more at an adult's face when she playfully pulled a toy away from them compared with when she simply handed them the toy. In Study 2, 7‐ and 9‐month‐old infants (N = 36) interacted with an adult who played a teasing game and then held a neutral or happy facial expression. Compared with a baseline in which infants looked equally to both expressions, after the tease, infants looked longer at the neutral compared with the happy expression. By 7 months, infants may use facial expressions to disambiguate others' actions.     

Illusory contour figures are perceived as occluding surfaces by 8‐month‐old infants

Infants have been demonstrated to be able to perceive illusory contours in Kanizsa figures. This study tested whether they also perceive these illusory figures as having the properties of real objects, such as depth and capability of occluding other objects. Eight‐ and five‐month‐old infants were presented with scenes that included a Kanizsa square and further depth cues provided by the deletion and accretion pattern of a moving duck. The 8‐month‐old infants looked significantly longer at the scene when the two types of occlusion cues were inconsistent than when they were consistent with each other, which provides evidence that they interpreted the Kanizsa square as a depth cue. In contrast, 5‐month‐olds did not show this difference. This finding demonstrates that 8‐month‐olds perceive the figure formed by the illusory contours as having properties of a real object that can act as an occluder.     

Inferring the size of a goal object from an actor's grasping movement in 6‐ and 9‐month‐old infants

The present study applied a preferential looking paradigm to test whether 6‐ and 9‐month old infants are able to infer the size of a goal object from an actor's grasping movement. The target object was a cup with the handle rotated either towards or away from the actor. In two experiments, infants saw the video of an actor's grasping movement towards an occluded target object. The aperture size of the actor's hand was varied as between‐subjects factor. Subsequently, two final states of the grasping movement were presented simultaneously with the occluder being removed. In Experiment 1, the expected final state showed the actor's hand holding a cup in a way that would be expected after the performed grasping movement. In the unexpected final state, the actor's hand held the cup at the side which would be unexpected after the performed grasping movement. Results show that 6‐ as well as 9‐month‐olds looked longer at the unexpected than at the expected final state. Experiment 2 excluded an alternative explanation of these findings, namely that the discrimination of the final states was due to geometrical familiarity or novelty of the final states. These findings provide evidence that infants are able to infer the size of a goal object from the aperture size of the actor's hand during the grasp.     

Twelve‐ to 14‐month‐old infants can predict single‐event probability with large set sizes

Previous research has revealed that infants can reason correctly about single‐event probabilities with small but not large set sizes ( Bonatti, 2008 ; Teglas et al., 2007 ). The current study asks whether infants can make predictions regarding single‐event probability with large set sizes using a novel procedure. Infants completed two trials: A preference trial to determine whether they preferred pink or black lollipops and a test trial where infants saw two jars, one containing mostly pink lollipops and another containing mostly black lollipops. The experimenter removed one occluded lollipop from each jar and placed them in two separate opaque cups. Seventy‐eight percent of infants searched in the cup that contained a lollipop from the jar with a higher proportion of their preferred color object, significantly better than chance. Thus infants can reason about single‐event probabilities with large set sizes in a choice paradigm, and contrary to most findings in the infant literature, the prediction task used here appears a more sensitive measure than the standard looking‐time task.     

Heart rate reactivity during contingency learning in 5‐ to 10‐month‐old at‐risk and non‐risk babies

The study investigated the dynamic relation between contingency learning and heart rate with risk and non‐risk babies 5‐ to 10‐months‐old. Four groups were compared in a two contingency treatments (contingent, yoked) × two risk status design. Concurrent heart rate was monitored during three phases of a contingency learning task (baseline, contingency/stimulation, extinction) and analysis focused on phase transitions. Non‐risk babies presented with contingent stimulation showed an immediate increase in cardiac rate associated with a subsequent response increase to the contingency. Risk infants presented with contingent stimulation showed delayed cardiac reactivity accompanied by a smaller response increase to the contingency. Yoked controls decreased responding in the contingent period with no significant changes in cardiac reactivity at phase transitions. The findings of the study are discussed in relation to individual differences in physiological regulation and to differential sensitization in a contingency learning task.     

Ten‐month‐old infants use prior information to identify an actor's goal

For adults, prior information about an individual's likely goals, preferences or dispositions plays a powerful role in interpreting ambiguous behavior and predicting and interpreting behavior in novel contexts. Across two studies, we investigated whether 10‐month‐old infants’ ability to identify the goal of an ambiguous action sequence was facilitated by seeing prior instances in which the actor directly pursued and obtained her goal, and whether infants could use this prior information to understand the actor's behavior in a new context. Experiment 1 demonstrated that the goal preview impacted infants’ subsequent action understanding, but only if the preview was delivered in the same room as the subsequent action sequence. Experiment 2 demonstrated that infants’ failure to transfer prior goal information across situations arose from a change in the room per se and not other features of the task. Our results suggest that infants may use their understanding of simple actions as a leverage point for understanding novel or ambiguous actions, but that their ability to do so is limited to certain types of contextual changes.     

10‐month‐old infants’ inference of invisible agent: Distinction in causality between object motion and human action1

Abstract: Two habituation experiments investigated 10‐month‐old infants’ interpretation of events where a stationary object began to move without any visible causes. During habituation, infants saw that an object partly hidden by an occluder began to move away from the occluder. Then, they were tested with three test events without the occluder: the ?rst event showed a hand pushing the object, the second event showed a hand failing to touch the object, and the last event had no agent. The objects were a ball in Experiment 1, and a person in Experiment 2. The test event that the infants looked at for the shortest duration in Experiment 1 was where the hand pushed the ball, whereas they looked at the three test events almost equal amounts of time in Experiment 2. These results indicate that 10‐month‐old infants responded to the events in terms of causality and could infer the presence of the agent behind the occluder only when they saw the habituation event featuring the ball.     

Humour Perception and Creation between Parents and 3‐ to 6‐month‐old Infants

Humour and laughter are universal to the human psychological experience and have serious developmental and evolutionary implications. Despite the early emergence of laughter in infancy, infants have been largely ignored in the humour research and humour has been largely ignored in the infant research. The present study describes the emergence of humour perception and creation in a sample of 20 parent–infant dyads who were followed from ages 3‐to‐ 6 months. The study examined how infants discover that absurd nonverbal behaviour, known as ‘clowning’, is amusing in the context of social engagement with caregivers. Results indicate that parents primarily use clowning when attempting to amuse their infants and pair these behavioural absurdities with affective cues like smiling and laughing. As they got older, infants were more likely to laugh and smile in response to clowning. Infants' ability to create humor via clowning also increased with age, starting with simple shrieks at 3 months to imitating absurd actions by 5 months. These increases are partly potentially explained by accompanying increases in parental smiling, laughing and clowning in response to infant clowning. Future research should employ more diverse samples and experimentally investigate the role of parental affect and social referencing in infants' interpretation of absurd behavior. Copyright © 2011 John Wiley & Sons, Ltd.     

Development of the perception of object containment in 9‐ to 16‐month‐olds

In the present study, 9‐, 12‐ and 16‐month‐old infants were familiarized to a block that was repeatedly lowered into a container and lifted from that container again. In the subsequent test phase, the block passed through the container opening either without making contact with the container rim or colliding with the rim in three places but ‘magically’ passing through. In Experiment 1 an opaque black screen was positioned just below the blocks' starting position. In Experiment 2 the screen was put at the height of the container rim and thus occluded the critical arrival phase of the trajectory. Results showed that looking times depended on what infants perceived as happening at the height of the rim and not on what they could have perceived before the block reached the opening, such as the absolute size of the objects. In contrast, older infants looked longer at an obstructed passage of the block into the container, irrespective of the position of the screen.     

Object individuation in young infants: Further evidence with an event-monitoring paradigm

Recent results indicate that, when tested with an event-monitoring task, 7.5- and 9.5-month-olds give evidence that they can individuate objects in different-objects occlusion events – events in which two distinct objects appear successively on either side of an occluder (Wilcox and Baillargeon, in press). The present research sought to confirm and extend these findings. The experiments examined 7.5- and 4.5-month-olds’ ability to correctly interpret a different-objects (ball-box condition) and a same-object (ball-ball condition) occlusion event. The infants in the ball-box condition saw a test event in which a ball disappeared behind the left edge of a screen; after a pause, a box emerged from behind the screen's right edge. For half of the infants (wide-screen event), the screen was wide and could occlude the ball and box simultaneously; for the other infants (narrow-screen event), the screen was narrow and should not have been able to occlude the ball and box at the same time. The infants in the ball-ball condition saw identical wide- and narrow-screen events except that the ball appeared on both sides of the screen. The infants in the ball-box condition looked reliably longer at the narrow- than at the wide-screen event, whereas those in the ball-ball condition tended to look equally at the events. These results suggest that the ball-box infants (a) were led by the featural differences between the ball and box to view them as distinct objects; (b) judged that the ball and box could both be occluded by the wide but not the narrow screen; and (c) were surprised in the narrow-screen event when this judgment was violated. In contrast, the ball-ball infants (a) assumed, based on the featural similarities of the balls that appeared on either side of the screen, that they were one and the same ball, and (b) realized that the ball could be occluded by either the wide or the narrow screen. These results indicate that, by 4.5 months of age, infants are able to use featural information to correctly interpret different-objects and same-object occlusion events. These findings are discussed in the context of the newly-drawn distinction between event-monitoring and event-mapping paradigms (Wilcox and Baillargeon, in press).     

Development of navigational working memory: Evidence from 6‐ to 10‐year‐old children

The ability to learn complex environments may require the contribution of different types of working memory. Therefore, we investigated the development of different types of working memory (navigational, reaching, and verbal) in 129 typically developing children. We aimed to determine whether navigational working memory develops at the same rate as other types of working memory and whether the gender differences reported in adults are already present during development. We found that navigational working memory is less developed than both verbal and reaching working memory and that gender predicts performance only for navigational working memory. Our results are in line with reports that children made significantly more errors in far space than adults, showing that near space representation develops before far space representation.     

A perceptual–attentional explanation of gaze following in 3‐ and 6‐month‐olds

Two experiments were conducted with 3‐ and 6‐month‐olds using a standard gaze following procedure with targets to examine the possibility that perceptual–attentional constraints may affect young infants’ gaze following. In Experiment 1, either moving or stationary targets were positioned at 15° from the infants’ midline. In Experiment 2, stationary targets were positioned at either 25° or 40° from the infants’ midline. Gaze following was evaluated with three criteria. Infants made significantly more correct responses to the 15° stationary targets than all other response types combined. When targets were moving or further away, infants made significantly more correct than incorrect responses when they made a turn; however, they did not make significantly more correct responses across all trials. It is argued that the infants’ responses are indicative of perceptual–attention constraints operating where the adult head and eye turn shifts infants’ attention to the side but whether the infants then ‘gaze follow’ depends on the structure of the environment as well as the infants’ ability to disengage attention and initiate saccadic eye movements.