Infants’ perception of musical patterns

This paper examines infants’ ability to perceive various aspects of musical material that are significant in music in general and in Western European music in particular: contour, intervals, exact pitches, diatonic structure, and rhythm. For the most part, infants focus on relational aspects of melodies, synthesizing global representations from local details. They encode the contour of a melody across variations in exact pitches and intervals. They extract information about pitch direction from the smallest musically relevant pitch change in Western music, the semitone. Under certain conditions, infants detect interval changes in the context of transposed sequences, their performance showing enhancement for sequences that conform to Western musical structure. Infants have difficulty retaining exact pitches except for sets of pitches that embody important musical relations. In the temporal domain, they group the elements of auditory sequences on the basis of similarity and they extract the temporal structure of a melody across variations in tempo.     

Infants’ enumeration of dynamic displays

This study examined infants’ enumeration of puppet jumping tasks. In Experiment 1, 5–7-month-old infants were familiarized to a puppet jumping two or three times, and tested with both numbers of jumps. Infants looked significantly longer at the new number, replicating Wynn [Psychol. Sci. 7 (1996) 164]. To probe further the stability of infants’ ability to enumerate, Experiment 2 varied the rate of the jumps during habituation and controlled for rate across test trials. At test, infants showed no preference for either event, suggesting that rate changes can overpower infants’ responses to number. Experiment 3 explored an alternative explanation to infants’ enumeration, namely discrimination based on the amount of time the puppet spent jumping. Infants were familiarized to two or three jumps, then tested with alternating displays of either a familiar number of jumps with a novel jump time, or a novel number of jumps with the familiar jump time. Infants dishabituated to the display that changed in jump time, but not to the display that changed in number. Results suggest that infants’ looking in event sequences is based on amount of motion, not enumeration. This finding is consistent with studies finding perceptual processes behind infants’ supposed precocious numerical abilities.     

Infants lost in (peripersonal) space?

A significant challenge in developing spatial representations for the control of action is one of multisensory integration. Specifically, we require an ability to efficiently integrate sensory information arriving from multiple modalities pertaining to the relationships between the acting limbs and the nearby external world (i.e. peripersonal space), across changes in body posture and limb position. Evidence concerning the early development of such spatial representations points towards the independent emergence of two distinct mechanisms of multisensory integration. The earlier-developing mechanism achieves spatial correspondence by representing body parts in their typical or default locations, and the later-developing mechanism does so by dynamically remapping the representation of the position of the limbs with respect to external space in response to changes in postural information arriving from proprioception and vision.     

Infants’ perception of depth from cast shadows

Five- and 7-month-old infants viewed displays in which cast shadows provided information that two objects were at different distances. The 7-month-olds reached preferentially for the apparently nearer object under monocular-viewing conditions but exhibited no reaching preference under binocularviewing conditions. These results indicate that 7-month-old infants perceive depth on the basis of cast shadows. The 5-month-olds did not reach preferentially for the apparently nearer object and, therefore, exhibited no evidence of sensitivity to cast shadows as depth information. In a second experiment, 5-month-olds reached preferentially for the nearer of two objects that were similar to those used in the first experiment but were positioned at different distances from the infant. This result indicated that 5-month-olds have the motor skills and motivation necessary to exhibit a reaching preference under the conditions of this study. The results are consistent with the hypothesis that depth perception based on cast shadows first appears between 5 and 7 months of age.     

Can Infants Have Interests in Continued Life?

The philosophers Peter Singer and Jeff McMahan hold variations of the view that infant interests in continued life are suspect because infants lack the cognitive complexity to anticipate the future. Since infants cannot see themselves as having a future, Singer argues that the future cannot have value for them, and McMahan argues that the future can only have minimal value for an infant. This paper critically analyzes these arguments and defends the view that infants can have interests in continuing to live. Even though infants themselves lack a strong psychological connection to the future, others who are involved in an infant’s life can anticipate, on an infant’s behalf, the kind of future that awaits the infant, and on the basis of this insight judge that continuing to live would be in the infant’s interests. After defending this position, I argue that this position on the interests of infants in continued life does not commit one to opposing abortion, and it does not commit one to the view that our ethical obligations to protect the lives of sentient animals are the same as our ethical obligations to protect infant lives.     

Infants’ emotional states influence maternal behaviors during holding

Previous studies have mainly examined how maternal behaviors influence infants during holding. However it is unclear how infants influence maternal holding. This current study investigated how infants’ emotional states influence maternal holding behaviors, and whether maternal holding behaviors are also influenced by the mothers’ parenting stress. We manipulated infants’ emotional states and videotaped mothers’ holding behaviors. The mothers also completed a questionnaire about their parental stress. Results showed that mothers varied their holding behaviors depending on their infants’ emotional states. When infants were comfortable, mothers rocked them horizontally and quietly. When infants were uncomfortable, mothers rocked them vertically at a high frequency. Furthermore, some types of parenting stress were related to several types of maternal behaviors in the context of holding. These findings suggest that maternal holding behaviors are influenced by both the infants’ emotional states and the mothers’ parenting stress.     

Infants’ sensitivity to allophonic cues for word segmentation

A series of four experiments was conducted to determine whether English-learning infants can use allophonic cues to word boundaries to segment words from fluent speech. Infants were familiarized with a pair of two-syllable items, such asnitrates andnight rates and then were tested on their ability to detect these same words in fluent speech passages. The presence of allophonic cues to word bound-aries did not help 9-month-olds to distinguish one of the familiarized words from an acoustically similar foil. Infants familiarized withnitrates were just as likely to listen to a passage aboutnight rates as they were to listen to one aboutnitrates. Nevertheless, when the passages contained distributional cues that favored the extraction of the familiarized targets, 9-month-olds were able to segment these items from fluent speech. By the age of 10.5 months, infants were able to rely solely on allophonic cues to locate the familiarized target words in passages. We consider what implications these findings have for understanding how word segmentation skills develop.

     

Infants’ discrimination of crossed and uncrossed horizontal disparity

In a series of preferential-looking experiments, infants 5 to 6 months of age were tested for their responsiveness to crossed and uncrossed horizontal disparity. In Experiments 1 and 2, infants were presented with dynamic random dot stereograms displaying a square target defined by either a 0.5° crossed or a 0.5° uncrossed horizontal disparity and a square control target defined by a 0.5° vertical disparity. In Experiment 3, infants were presented with the crossed and the uncrossed horizontal disparity targets used in Experiments 1 and 2. According to the results, the participants looked more often at the crossed (Experiment 1), as well as the uncrossed (Experiment 2), horizontal disparity targets than at the vertical disparity target. These results suggest that the infants were sensitive to both crossed and uncrossed horizontal disparity information. Moreover, the participants exhibited a natural visual preference for the crossed over the uncrossed horizontal disparity (Experiment 3). Since prior research established natural looking and reaching preferences for the (apparently) nearer of two objects, this finding is consistent with the hypothesis that the infants were able to extract the depth relations specified by crossed (near) and uncrossed (far) horizontal disparity.     

WAIMH position paper: Infants’ rights in wartime

The World Association for Infant Mental Health (WAIMH) decided to compose a position paper on infants’ rights in wartime, as there is still a general lack of attention paid to the impact of war-related traumas on infants’ development and psychological health. Though there are numerous areas of violent conflicts around the globe, there have been few published studies that relate specifically to infants. Consequently, humanitarian aid programs tend to overlook infants’ psychological needs and to pay more attention to those of older children. This position paper first reviews the studies identified through a literature search, about the impact of war-related traumas during pregnancy and postnatal periods, then describes the existing recommendations that have been added to the Children Rights Convention and their implications for infant mental health clinicians.     

Infants’ sensitivity to the depth cue of shading

Five- and 7-month-old infants were tested for sensitivity to the depth cue of shading. Infants were presented with two displays: a surface in which a convexity and a concavity were molded and a photograph in which shading specified a convexity and a concavity. Each display was presented under both monocular and binocular viewing conditions. Reaching was observed as the dependent measure. Infants in both age groups reached preferentially for the actual convexity in both the monocular and binocular viewing conditions. In the monocular photograph condition, the 7-month-olds reached preferentially for the apparent convexity specified by shading, indicating that they perceived it to be an actual convexity. These infants showed no significant reaching preference in the binocular photograph condition. This finding rules out interpretations of the infants’ reaching not based on perceived depth. The results therefore suggest that the 7-month-olds perceived depth from shading. The 5-month-olds showed no significant reaching preferences when viewing the photograph; thus, they showed no evidence of depth perception from shading. These findings are consistent with the results of a number of studies that have investigated infants’ sensitivity to pictorial depth cues. Together, these studies suggest that the ability to perceive depth from pictorial cues may first develop between 5 and 7 months of age.     

Parents’ Influence on Infants’ Gender-Typed Toy Preferences

Gender socialization influences children at early ages, shaping their developing identities. The toys provided by parents deliver some of the earliest gender-based messages by encouraging children to engage in activities associated with, for example, dolls and trucks. In the current study, we measured the influence of parental socialization by assessing 5- and 12 ½-month-old infants’ exposure to dolls and trucks and by experimentally manipulating parents’ encouragement to play with these toys. We found that infants displayed gender-typical toy preferences at 12 ½, but not 5 months, a pattern characteristic of previous studies. However, brief encouragement by a parent to play with toys from each category was ineffective in altering infants’ preferences. Rather, the types of toys present in the home predicted preferences, suggesting that at-home exposure to toys may be influential in the development of toy preferences. These findings reveal that socialization processes may indeed play a role in the formation of early gender-typical toy preferences and highlight the importance of equal toy exposure during infancy to ensure optimal development.     

Pacifiers Disrupt Adults’ Responses to Infants’ Emotions

Research shows that pacifiers disrupt infants' mimicry of facial expressions. This experiment examines whether pacifiers interfere with caretakers' ability to mimic infants' emotions. Adults saw photographs of infants with or without a pacifier. When infants had pacifiers, perceivers showed reduced EMG activity to infants' smiles. Smiles of infants using a pacifier were also rated as less happy than smiles depicted without a pacifier. The same pattern was observed for expressions of distress: adults rated infants presented with pacifiers as less sad than infants without pacifiers. We discuss deleterious effects of pacifier use for the perceiver's resonance with a child's emotions.     

Infants’ detection of increments in low- and high-frequency noise

A visually reinforced operant paradigm was employed to examine the relationship between the difference limen (DL) for intensity and level of the standard during infancy. In Experiment 1,7-month-old infants and adults detected increments in continuous noise presented via headphones at each of four levels ranging from 28 to 58 dB SPL. Noise stimuli were 2-octave bands centered at either 400 or 4000 Hz, and increments were 10 and 100 msec in duration. Infants’ DLs were significantly larger than those of adult subjects and significantly larger for low- than for high-frequency stimuli. For the high-frequency noise band, infants’ DLs were generally consistent with Weber’s law,remaining essentially constant for standards higher than 28 dB SPL (3 dB SL) for 100-msec increments and 38 dB SPL (13 dB SL) for 10-msec increments. For low-frequency noise, infants’ absolute thresholds were exceptionally high, and sensation levels of the standards were too low to adequately describe the relationship. In Ex-periment 2, 7-month-old infants detected 10- and 100-msec increments in 400-Hz noise stimuli presented in sound field. Infants’ low-frequency DLs were large at low intensities and decreased with increases in level of the standard up to at least 30 dB SL. For both low- and high-frequency noise, the difference between DLs for 10- and 100-msec increments tended to be large at low levels of the standard and to decrease at higher levels. These results suggest that the relationship between the DL and level of the standard varies with both stimulus frequency and duration during infancy. However, stimulus-dependent immaturities in increment detection may be most evident at levels within approximately 30 dB of absolute threshold.     

Infants and toddlers discriminate amount: are they measuring?

Four experiments that show an early ability to encode and retain information about extent are presented. We found that infants discriminate between the heights of dowels in a habituation task. We also found that toddlers discriminate between heights on a choice task in which a target dowel is presented and removed and they then choose between the target and a foil. Until 4 years of age, however, discrimination occurs only in the presence of a perceptually salient standard. Adults do not require a perceptually present standard; they can assess extent across temporal or spatial gaps by imposing a standard (measure). The present findings indicate that infants and toddlers do not possess an adult ability to establish extent, but that they do possess a skill that provides a start point for this important intellectual achievement.     

Infants’ representations of same and different in match- and non-match-to-sample

Three experiments investigated the representations that underlie 14-month-old infants’ and adults’ success at match-to-sample (MTS) and non-match-to-sample (NMTS) tasks. In Experiment 1, 14-month-old infants were able to learn rules based on abstract representations of sameness and/or difference. When presented with one of eighteen sample stimuli (A) and a choice between a stimulus that was the same as the sample (A) and a different stimulus (B), infants learned to choose A in MTS and B in NMTS. In Experiments 2 and 3, we began to explore the nature of the representations at play in these paradigms. Experiment 2 confirmed that abstract representations were at play, as infants generalized the MTS and NMTS rules to stimuli unseen during familiarization. Experiment 2 also showed that infants tested in MTS learned to seek the stimulus that was the same as the sample, whereas infants tested in NMTS did not learn to seek the different stimulus, but instead learned to avoid the stimulus that was the same as the sample. Infants appeared to only use an abstract representation of the relation same in these experiments. Experiment 3 showed that adult participants, despite knowing the words “same” and “different”, also relied on representations of sameness in both MTS and NMTS in a paradigm modeled on that of Experiment 2. We conclude with a discussion of how young infants may possibly represent the abstract relation same.     

Infants’ identification of three-dimensional form from transformations of linear perspective

The ability of infants to perceive three-dimensional structure from transformations of linear perspective was investigated in two studies. Infants were habituated to the pattern of linear perspective transformations corresponding to a particular three-dimensional object, and their relative preference for that object as compared with a different three-dimensional object was assessed both before and after habituation. The habituation displays showed the distorting shadow cast by a rotating object and therefore provided only transformations of linear perspective as information specifying three-dimensional form. The pre- and posttest displays involved the actual three-dimensional objects and provided binocular, shading, and texture information specifying three-dimensional form, but did not provide informative transformations of linear perspective. In Study 1, 6-month-olds showed changes in preference from pre- to posttest that were related to the identity of the object whose shadow they had seen during habituation; 4-month-olds, however, did not show preference changes related to the habituation object. In Study 2, rhythm information that may have served as a basis for responding in Study 1 was eliminated from the test displays. Six-month-olds again showed changes in preference that were dependent on their habituation experience. It is concluded that, by 6 months of age, infants are able to perceive object structure from the isolated cue of transformations of linear perspective. The findings are discussed with reference to infants’ three-dimensional form perception based on other cues and also with reference to the emergence of certain spatially related moter activities.