Cross-modal transfer in 6-month-old infants.

Investigated in 4 studies with 101 infants 25.5–32 wks of age the ability of Ss to transfer information about shape across modalities. Ss were familiarized either orally or tactually and then tested for visual recognition memory. In Exp I, Ss failed to show evidence of cross-modal transfer on any of the tasks (1 oral–visual, 2 tactual–visual). When familiarization times were increased from 30 to 60 sec in Exp II, Ss showed evidence of transfer on both tactual–visual tasks. Exp III eliminated the 5–7 sec delay that generally intervenes between the familiarization and test phase. Ss were permitted to retain the stimulus in their hand (or mouth) during the test phase while simultaneously viewing a novel stimulus and a duplicate of the familiar stimulus. This modification resulted in successful transfer on 1 of the 2 tactual–visual tasks. Ss did not show evidence of transfer on the oral–visual problem in any of these studies, despite evidence from Exp IV that they could visually discriminate the paired stimuli used in these tasks and that they showed recognition memory when familiarization and testing were both visual. Results suggest that, although cross-modal transfer of information about shape is present among 6-mo-olds, it is a less robust phenomenon than that seen in older infants. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object and event representation in 6?-month-old infants.

Two experiments were conducted in which infants had to use remembered knowledge of auditory visual events to guide their reaching and grasping. The events involved a ball falling noisily through a tube and coming to rest at 1of 2 locations, with either resting site specified by distinctive auditory information. The events were presented initially in the light and then in the dark to determine whether infants would remember and use the auditory cues when they could no longer see where the ball fell. In both experiments, infants' reaching behavior was initiated and carried out after the sound ended, which ensured that search for the ball took place without support from ongoing visual or auditory cues. Accurate searching for the ball depended on infants' experience in the light. The authors conclude that 6 ?-month-olds can represent unseen objects and events and use this knowledge to guide their actions to achieve a goal. The success in this task was contrasted with the failures of infants this age in the Piagetian hidden object task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bisensory response to temporal frequency in 4-month-old infants.

Three studies investigated detection of auditory–visual equivalence of rate among 55 4-mo-olds. In the 1st 2 studies, Ss were shown pairs of check patterns flashing at 2, 4, and 8 Hz either in silence or while listening to a tone corresponding in rate to 1 member of the pair. In Study 1, rate of stimulation varied, whereas duty cycle (i.e., intensity) was kept constant. No evidence of bisensory matching of rate was found. In Study 2, rate and duty cycle covaried. Although no matching was found, the presence of the 2 most intense sounds led to a shift in looking toward lower rates of visual stimulation. In Study 3, rate was kept constant (2 Hz), whereas duty cycle was varied. No matching was found, but as in Study 2, the presence of the most intense sound led to a shift in looking toward the less intense visual stimuli. Although these findings are contrary to previous reports of auditory–visual matching of rate, they do indicate that sound influences visual preferences via an intensity-based response mechanism. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory temporal pattern perception in 6- and 12-month-old infants.

A go/no-go conditioned head-turn paradigm was used to examine 20 6- and 20 12-mo-olds' abilities to discriminate changes in temporal grouping and their perception of absolute and relative timing information when listening to patterns of white-noise bursts. 6-mo-olds performed absolute timing discriminations both when the number of groupings of a pattern were changed and when the number of groupings remained invariant and the duration parameters of elements comprising a single group were altered. They did not, however, reliably discriminate changes in relative timing information that resulted in the number of groups remaining invariant while the number of elements comprising a group changed. 12-mo-olds readily performed both types of temporal grouping discriminations, demonstrating equally high performance for absolute and relative timing-discrimination conditions. For the absolute timing parameters tested, there was no evidence of any age-related change in the temporal resolving power of the auditory system. Ss at both ages reliably performed signal–silence duration discriminations spanning .04–.06 to .10–.15 sec. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Brain activity differentiates face and object processing in 6-month-old infants.

Event-related potentials were used to determine whether infants, like adults, show differences in spatial and temporal characteristics of brain activation during face and object recognition. Three aspects of visual processing were identified: (a) differentiation of face vs. object (P400 at occipital electrode was shorter latency for faces), (b) recognition of familiar identity (Nc, or negative component, at frontotemporal electrodes [FTEs] was of larger amplitude for familiar stimuli), and (c) encoding novelty (slow wave at FTEs was larger for unfamiliar stimuli). The topography of the Nc was influenced by category type: Effects of familiarity were limited to the midline and right anterior temporal electrodes for faces but extended to all temporal electrodes for objects. Results show that infants' experience with specific examples within categories and their general category knowledge influence the neural correlates of visual processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sequential analysis of mastery behavior in 6- and 12-month-old infants.

We examined the pattern and direction of behaviors that reflect infants' underlying mastery motivation. The sequences of mastery behavior were analyzed in a sample of 67 infants when they were 6 and 12 months old. We computed (a) the frequencies of each of 6 categories of mastery behavior, transitional probabilities, and z scores for each possible behavior change between the categories and (b) the transitions from a mastery behavior to an instance of positive affect. The analyses revealed significant age changes in the frequency of each category; however, the significant transitional probabilities among the six categories displayed a similar organization at both ages. The transitions from a mastery behavior to an instance of positive affect suggest that it is persistent, goal-directed behaviors that contribute to an infant's feeling of efficacy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The still-face effect in Chinese and Canadian 3- to 6-month-old infants

Both green and black tea have been shown to inhibit lung tumorigenesis in laboratory animal experiments. Green tea inhibited N-nitrosodiethylamine-induced lung tumor incidence and multiplicity in female A/J mice when tea was given either during the carcinogen treatment period or during the post-carcinogen treatment period. In a separate tumorigenesis model, both decaffeinated black tea and decaffeinated green tea inhibited 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumor formation. Studies in which tea was administered during different time periods in relation to the NNK suggest that tea can inhibit lung tumorigenesis at both the initiation and promotion stages. The antiproliferative effects of tea may be responsible for these anti-carcinogenic actions. Black tea polyphenol preparations decreased NNK-induced hyperproliferation. Black tea also inhibited the progression of pulmonary adenomas to adenocarcinomas and the formation of spontaneous lung tumors in A/J mice. Growth inhibition by various tea polyphenols has been demonstrated in human lung H661 and H1299 cells. Although inhibition of cell growth and signal transduction pathways by tea components have been demonstrated, the concentrations required to produce the effect are higher than achievable in tissues in vivo. More research is necessary to translate these laboratory results to applications in human chemoprevention.     

Reinforced variability and operant learning.

Reinforcement of variability may help to explain operant learning. Three groups of rats were reinforced, in different phases, whenever the following target sequences of left (L) and right (R) lever presses occurred: LR, RLL, LLR, RRLR, RLLRL, and in Experiment 2, LLRRL. One group (variability [VAR]) was concurrently reinforced once per minute for sequence variations, a second group also once per minute but independently of variations, that is, for any sequences (ANY), and a control group (CON) received no additional reinforcers. The 3 groups learned the easiest targets equally. For the most difficult targets, CON animals' responding extinguished whereas both VAR and ANY responded at high rates. Only the VAR animals learned, however. Thus, concurrent reinforcers—contingent on variability or not—helped to maintain responding when difficult sequences were reinforced, but learning those sequences depended on reinforcement of variations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Action-schemes of 8-month-old infants.

Observed 64 infants, equally divided by sex and term or preterm birth, to examine the influence of preterm birth and sex on action-schemes. Both groups demonstrated the same types of action-schemes and spent similar proportions of time involved in direct object explorations. Group differences were apparent in the duration of individual action-schemes, particularly the low duration of mouthing observed with the preterm males. It is suggested that this atypical behavior in these Ss reflects a subtle aspect of behavioral disorganization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal bisection in 4-month-old infants.

The present study was the first to investigate infants' ability to discriminate time using a bisection task that has been extensively used with animals and human adults. Infants aged 4 months were presented with two standard auditory signals, one short (S = 500 ms) and one long (L = 1,500 ms), and were trained either to look to the left after S and to the right after L, or vice versa. During the test phase, the infants were then presented with intermediate durations without reinforcement as well as the two reinforced standard durations, for which the reinforcement was either immediate or delayed of 3 s. The times spent by the infants looking to the right, left or away from the target after the stimulus duration were coded by two blind coders. The results revealed an orderly psychophysical function with the proportion of long responses increasing with signal duration. The point of subjective equality (Bisection Point) was closer to the geometric mean of the short and long standard duration than to their arithmetic mean. Modeling using the scalar timing models revealed that our infants had a relatively high sensitivity to time but that their temporal performance was affected by the fact that they made a large number of random responses. The development of the perception of time is discussed in the light of similarities and differences in temporal bisection performance between different species (rats and humans) and the different levels of development observed within a given species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Right frontal brain activity, cortisol, and withdrawal behavior in 6-month-old infants.

Although several studies have examined anterior asymmetric brain electrical activity and cortisol in infants, children, and adults, the direct association between asymmetry and cortisol has not systematically been reported. In nonhuman primates, greater relative right anterior activation has been associated with higher cortisol levels. The current study examines the relation between frontal electroencephalographic (EEG) asymmetry and cortisol (basal and reactive) and withdrawal-related behaviors (fear and sadness) in 6-month-old infants. As predicted, the authors found that higher basal and reactive cortisol levels were associated with extreme right EEG asymmetry. EEG during the withdrawal-negative affect task was associated with fear and sadness behaviors. Results are interpreted in the context of the previous primate work, and some putative mechanisms are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electroencephalogram asymmetry in response to the approach of a stranger and maternal separation in 10-month-old infants.

We recently reported the presence of reliable asymmetries in frontal-brain electrical activity in infants that distinguished between certain positive- and negative-affect elicitors. In order to explore the degree to which these asymmetries in brain activity are associated with individual differences in affective response, 35 ten-month-old female infants were presented with a stranger-approach, mother-approach, and maternal-separation experience while an electroencephalogram (EEG) from the left- and right-frontal and left- and right-parietal scalp regions was recorded and facial and other behavioral responses were videotaped. Changes in frontal-EEG asymmetry reflected behavioral changes between conditions. In addition, individual differences in affective response to separation were related to differences in frontal-brain asymmetries. These findings indicate that lawful changes exist in asymmetries of frontal-brain activation during the expression of certain emotions in the first year of life and that individual differences in emotional responsivity are related to these measures of brain activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The perception of structure in vectorpatterns by 4-month-old infants.

30 infants (aged 3 mo 26 days to 4 mo 14 days) were habituated to 3 vectorpatterns consisting of 2-dimensional arrays of short line segments in 19 15-sec trials. Two of the vectorpatterns used in the study were well structured and consisted of either concentric circles or radial lines. In the 3rd vectorpattern the line segments were randomly oriented. In each pattern the location of the line segments was the same. Ss who habituated to 1 well-structured pattern showed recovery of looking to (1) the 2nd pattern and (2) the random pattern. However, Ss habituated to the random pattern did not recover looking to either structured pattern. It is argued that vectorpatterns could be a useful means of investigating perceptual organization in Ss' vision, as they have been with adults. (French abstract) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Control of operant response force.

Differences in motor-control strategies (feedback or feedforward) engaged by rats to produce operant response force were investigated under 2 conditions of external feedback. In the immediate condition, liquid sucrose reinforcers were delivered as soon as each forelimb response met the force requirement, whereas under the terminal condition, reinforcers were delivered at response termination. When feedback control of response force was precluded by delivering reinforcers at response termination, force was adjusted by modulation of the rate of rise of force. However, under immediate reinforcer delivery, response force was controlled by adjustments of time to peak force. Such adjustments of response time to meet response requirements of increasing difficulty are consonant with expressions of the speed–accuracy tradeoff commonly observed in studies of human motor control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perception of object unity in 2-month-old infants.

The perception of object unity in partial occlusion displays was examined in 72 2-month-old infants. The infants were habituated to 1 of 3 displays depicting a rod undergoing lateral motion behind a box. In each display, more of the rod was visible behind the box than was previously available in prior studies of young infants' perception of occlusion. Posthabituation test displays consisted of 2 rod pieces (broken rod) and a complete rod, presented 3 times each in alternation. Infants in all 3 conditions looked longer at the broken rod than at the complete rod, suggesting that the hidden region of the rod in the habituation display was inferred despite the absence of direct perceptual support. These findings suggest that very young infants' visual, attentional, or cognitive skills may be insufficient to consistently support perception of object unity, except under some display conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Detection of stimulus motion in 5-month-old infants.

Five-month-old infants were tested by the method of preferential looking for discrimination between a pattern undergoing oscillating apparent motion and an identical static pattern. Sensitivity to small spatial displacements was evident at temporal frequencies of 8 and 16 Hz. Preference for the moving display was related independently to the temporal frequency of oscillation and the magnitude of the spatial displacement. Preferences for the moving display increased asymptotically across spatial displacements from 11 to 89 arc min. Preferences peaked between temporal oscillation frequencies of 8 and 16 Hz. Preference was not related to the ratio of these two variables—velocity. The minimum displacement threshold of 7.36 arc min was found to depend on the size of the elements in the pattern and on the temporal frequency of oscillation. The results demonstrate that motion-sensitive mechanisms responsive to small spatial displacements are present at 5 months of age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of operant escape learning in the Peking duck embryo.

Peking duck embryos were trained in an operant escape task during the last 4 days of a 27-day incubation period. In this task, termination of a mild shock applied to the wing could be accomplished by a discrete foot flexion. Response latencies were recorded and compared for groups in which shock offset was contingent on emission of the correct response (contingent shock groups) and groups in which no such contingency was imposed (noncontingent shock groups). In the Day 24, 25, and 26 embryos, the latency of foot flexion was significantly shorter in the contingent shock groups during the escape training trials, which indicated the establishment of an association between the operant escape response and shock termination. The Day 23 embryos were not able to acquire the escape response. Results demonstrate that the avian embryo is more than a passive recipient of incoming information and can actively operate on externally imposed input in such a way as to adaptively alter stimulus contingencies. Such a capability is congruent with theories of behavioral development that hypothesize the gradual building up of postnatal response patterns during the prenatal period. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory evoked potentials and hand preference in 6-month-old infants: Possible gender-related differences in cerebral organization.

Normal 6-mo-old infants (10 male and 10 female) were studied to determine if cortical auditory evoked potentials (EPs) recorded to probe stimuli during verbal and musical stimulus presentation provided an index of cerebral functional organization. Furthermore, EP left–right amplitude asymmetries were examined in relation to gender differences and hand-reaching preference in these infants. Six-mo-old girls exhibited EP amplitude asymmetries associated with the stimulus conditions, whereas boys did not. In addition, both boys and girls showed associations between their patterns of EP asymmetry and their hand-reaching preference. The patterns of electrophysiological responses observed and their relation to hand preference suggest that the rate of maturation of the left and right hemispheres differs and is dependent on the gender of the infant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)