Infants' localization of sounds along the horizontal axis: Estimates of minimum audible angle.

Localization acuity was examined by determining the smallest sound shift off midline and along the horizontal axis that infants could reliably discriminate (i.e., minimum audible angle). Infants 6, 9, 12, 15, and 18 months of age were seated in a dark room facing an array of nine loudspeakers positioned along the horizontal axis and at ear level. One loudspeaker was positioned at midline, 0°, and four others each were positioned to the right and left of 0°. A two-alternative forced-choice procedure was used in conjunction with a method of constant stimuli. A sequence of white-noise bursts was presented initially at 0° and was then shifted horizontally (right or left of 0°). The sequence continued to be presented until the infant made a directional head or eye movement, or both. Correct responses were visually reinforced. With increasing age, infants demonstrated a finer partitioning of auditory space along the horizontal axis. At 6 months, only a location shift of at least 12° off midline was reliably discriminated, whereas, by 18 months, infants reliably discriminated a shift of only 4°. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Global precedence: The effect of exposure duration.

Stimuli consisting of large letters constructed from small letters were presented to 26 undergraduates for 10, 40, or 100 msec, and Ss were required to identify either the large letters or the small letters. At the 10-msec exposure duration, only unidirectional or global to local interference was observed. This finding is consistent with D. Navon's (see record 1978-11488-001) global precedence hypothesis. However, at the longer exposure durations equivalent global to local and local to global interference patterns were observed. Results limit the generality of any global precedence hypothesis, either perceptual or attentional, to conditions in which there are large discrepancies in the quality of the local and global information. (French abstract) (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of eccentricity and size in the global precedence effect.

The global precedence hypothesis was investigated in a series of experirnents by considering the effects of eccentricity and size and their possible interaction on the speed of processing of both global and local levels of compound stimuli. Furthermore, the possible effect of size-eccentricity uncertainty on the temporal order of processing was examined across eccentricity. The results showed a global advantage in speed of processing regardless of experimental presentation conditions when the confound of eccentricity was controlled. Somewhat surprisingly, the pattern of response times as a function of eccentricity was quadratic. Subsequent experiments indicated that the quadratic functions obtained result from the summed individual effects of size and eccentricity. The results indicate that size and eccentricity are the main determinants of the global advantage effect and that many previous findings may be explained in terms of these effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physiological studies of the precedence effect in the inferior colliculus of the kitten

The precedence effect (PE) is a perceptual phenomenon that reflects listeners' ability to suppress echoes in reverberant environments. The PE is not present at birth and appears only several months postnatal. Recent physiological studies have demonstrated correlates of the PE in the central nucleus of the inferior colliculus (ICC) of adult animals. The present study extended the same techniques to search for similar correlates in the ICC of kittens during the first postnatal month. Stimuli consisted of pairs of clicks or noise bursts presented from different locations in free field or with different inter-aural differences in time (ITD) under headphones, with an inter-stimulus-delay (ISD) between their onsets. Results suggest that a physiological correlate of the PE, i.e. suppression of responses to the second source, is present as early as 8 days postnatal, and occurs at similar ISDs to those recorded in adult cats. Suppression in kitten neurons varies with stimulus level, duration, and azimuthal position, in a similar manner to that in adult neurons. The age at which correlates of the PE in the kitten can be found precedes the age at which kittens can localize sound sources effectively, and presumably before the age at which they would demonstrate the PE behaviorally. Thus, the neural mechanisms that might be involved in the first stages of processing PE stimuli may be in place well before the behavioral correlate develops.     

Echo suppression and discrimination suppression aspects of the precedence effect

The precedence effect is a phenomenon that may occur when a sound from one direction (the lead) is followed within a few milliseconds by the same or a similar sound from another direction (the lag, or the echo). Typically, the lag sound is not heard as a separate event, and changes in the lag sound's direction cannot be discriminated. The hypothesis is proposed in this study that these two aspects of precedence (echo suppression and discrimination suppression) are at least partially independent phenomena. Two experiments were conducted in which pairs of noise bursts were presented to subjects from two loudspeakers in the horizontal plane to simulate a lead sound and a lag sound (the echo). Echo suppression threshold was measured as the minimum echo delay at which subjects reported hearing two sounds rather than one sound; discrimination suppression threshold was measured as the minimum echo delay at which subjects could reliably discriminate between two positions of the echo. In Experiment 1, it was found that echo suppression threshold was the same as discrimination suppression threshold when measured with a single burst pair (average 5.4 msec). However, when measured after presentation of a train of burst pairs (a condition that may produce "buildup of suppression"), discrimination suppression threshold increased to 10.4 msec, while echo suppression threshold increased to 26.4 msec. The greater buildup of echo suppression than of discrimination suppression indicates that the two phenomena are distinct under buildup conditions and may be the reflection of different underlying mechanisms. Experiment 2 investigated the effect of the directional properties of the lead and lag sounds on discrimination suppression and echo suppression. There was no consistent effect of the spatial separation between lead and lag sources on discrimination suppression or echo suppression, nor was there any consistent difference between the two types of thresholds (overall average threshold was 5.9 msec). The negative result in Experiment 2 may have been due to the measurements being obtained only for single-stimulus conditions and not for buildup conditions that may involve more central processing by the auditory system.     

Developmental changes in tritium autoabsorption

Developmental changes in autoabsorption of tritium emissions were examined in 30 brain regions in the rat at Postnatal Days 0, 4, 7, 10, 14, 21, and 28 and adulthood. Rats received tritiated 2-deoxyglucose in vivo. Alternate brain sections were extracted in chloroform, and autoradiographs were developed from extracted and nonextracted sections. The ratio of optical density values in extracted vs nonextracted sections was used to determine autoabsorption for each structure. Three principal temporal patterns in the development of adult levels of autoabsorption, determined by the optical density ratios, were identified: (1) a minimal increase pattern in which autoabsorption rose only slightly between birth and adulthood; (2) a plateau pattern in which a rapid early increase was followed by stable values; and (3) a late increase pattern in which autoabsorption remained relatively constant until Postnatal Day 28, with a large increase between Day 28 and adulthood. In addition, optical density ratios fluctuated during the second postnatal week in close to one-third of the structures. The data suggest that developmental events affecting the ratio of gray to white matter produce substantial local variations in the development of adult levels of autoabsorption that are distinct for each structure. To correct for autoabsorption effects in ontogenetic studies using tritium autoradiography, it is necessary to determine directly the degree of autoabsorption at a particular time point for the structure of interest. Our results indicate that the technique of in vivo administration of tritiated 2-deoxyglucose followed by chloroform extraction appears to be a sensitive and reproducible method for assessing autoabsorption at all ages.     

Developmental changes in the attribution of blame.

A story completion test was constructed to measure developmental changes in the methods used by children to assign blame in situations where the cause of unpleasant events was left ambiguous. Ss were 115 elementary school children between the ages of 5 and 12 years. The tendency to blame others decreased with age whereas responses involving sharing of blame or recognition of impersonal and accidental causes increased with age. The story completion method provides a simple way of measuring behavior in this important area of personality development. The findings suggest that a valuable tool for personality assessment of children could be constructed from the stories used in the present study together with story completion items designed to tap mechanisms for coping with other critical stress situations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental changes in the voltage-dependence of neocortical NMDA responses

A change in the response of neocortical neurons to N-methyl-D-aspartate (NMDA) was observed during the first 2 weeks of postnatal development. When NMDA was bath applied, the membrane current-voltage relationship recorded in neurons from postnatal day (PN) 3-5 rats displayed a region of decreased inward current at hyperpolarized membrane potentials. By PN 9-14, the net inward current at hyperpolarized potentials was significantly less than that recorded in PN 3-5 neurons. These results indicate that a developmental increase in the voltage-dependence of NMDA responses exists, which may be due to changes in magnesium sensitivity of the NMDA receptor.     

Developmental changes in the organization of prereaching movements.

Examined how the kind and amount of prereaching activity change with age during the period preceding successful grasping of objects. 23 infants were tested at 3-wk intervals from the 1st week of life to 16 wks of age. 12 Ss were also seen at 19 wks of age. At each session, the S was presented with an object moving slowly in different ways in front of him or her. In the middle of each session there was also a 1-min period with no object present. Results show that the amount of prereaching declined at 7 wks and that this decrease was contingent on the presence of the object. Ss did not seem to lose interest in the object at this age, but attending to the object inhibited prereaching activity in some way. The form of prereaching also changed at 7 wks, with the fist clenched during the forward extension of the arm. After this age, the amount of prereaching activity again increased and the hand opened during the forward extension, but only when the S looked at the object. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental changes in word recognition strategies

Attempted to determine when children develop adultlike strategies in word recognition and use the entire configuration as a basis for a response rather than individual letters. A total of 144 kindergartners, 1st-6th graders, and undergraduates were asked to choose an alternative which most resembled a stimulus trigram, quadrigram, or quingram. Ss could respond on the basis of individual letter position and overall word shape. There was a clear developmental trend such that, with increasing age, Ss were more likely to choose alternatives with the same shape as the stimulus. There was also a tendency to choose response alternatives with the same 1st letter as the stimulus through 4th grade, followed by a decreasing tendency to rely on the 1st letter starting with the 5th grade. Results are considered supportive of E. J. Gibson's (see record 1972-22179-001) hypothesis of a developmental change with increasing age and schooling in feature analysis and extraction. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental changes in processing speed: Influence of speed-accuracy regulation.

We investigated the possibility that marked improvements in speed of information processing from early childhood to adulthood reflect improved speed–accuracy monitoring and regulation. Trial-by-trial examination of reaction time (RT) and accuracy transitions during serial choice RT performance revealed developmental changes in accuracy monitoring and speed regulation; these changes corresponded to the most pronounced age-related changes in average RT. For 5-year-olds, poor control over speed of responding, coupled with inconsistent accuracy monitoring, resulted in less orderly trial-to-trial RT transitions and a consequent failure to constrain responses within fast RT bands just safely above overly fast error RT levels. Control over speed of responding was improved by age 7, but inconsistent accuracy monitoring was still a factor. From age 9 up to adulthood, subjects monitored accuracy consistently and showed quite precise control over speed of responding. These developments were associated with a marked improvement in RT constraint within narrow, fast RT bands. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Shifting perceptions: Developmental changes in judgments of melodic similarity.

Musical melodies are recognized on the basis of pitch and temporal relations between consecutive tones. Although some previous evidence (e.g., Saffran & Griepentrog, 2001) points to an absolute-to-relative developmental shift in listeners' perception of pitch, other evidence (e.g., Plantinga & Trainor, 2005; Schellenberg & Trehub, 2003) suggests that both absolute- and relative-pitch processing are evident among listeners of all ages (infants, children, and adults). We attempted to resolve this apparent discrepancy by testing adults as well as children 5–12 years of age. On each trial, listeners rated how similar or how different 2 melodies sounded. The melodies were identical, transposed (all tones shifted in pitch by the same amount), different (same tones reordered, changing pitch relations between successive tones), or transposed and different. Listeners of all ages were sensitive to both changes, but younger listeners attended selectively to transpositions as a source of perceived differences. With increasing age, melodic differences played an increasingly important role, whereas transpositions became less relevant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental changes in the infants attention to pattern detail

To assess developmental changes in the importance of stimulus intensity and pattern detail for infants' visual attention, infants of 10, 17, and 25 wk. of age were shown pairs of stimuli equated for stimulus intensity but different in pattern detail (angles or straight lines). The youngest infants gave equivalent amounts of attention to the stimuli of each pair while the two older groups showed a significant preference for the angular stimuli. The results are interpreted as showing the increased attention to elements with development, and a possible explanation of the preference for the angle stimuli is discussed.     

Developmental changes in the time-dependent nature of memory retrieval.

Six-month-old infants trained in an operant conditioning procedure were allowed to forget the contingency and were presented with a reminder in a memory-reactivation paradigm. The time course of memory retrieval after the reminder, the relation between the forgetting functions of the newly acquired and the reactivated memory, and the potential contribution of the context to retention after long delays were investigated. Memory retrieval was found to be a time-locked process at 6 months, as at 3 months. Although retrieval was more rapid at the older age, the reactivated memory was more transient than the newly acquired memory at 6 months and remained accessible for a briefer period than at 3 months. A distinctive context was requisite for memory reactivation at 6 months but did not insure it. These studies reveal that the temporal parameters of memory processing change with age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Global precedence in visual search? Not so fast: evidence instead for an oblique effect

We used the dual-task paradigm to provide evidence that inferring the motion of a component of a mechanical system (mental animation) is a spatial visualization process. In two experiments, participants were asked to solve mental animation problems while simultaneously retaining either a visuospatial working memory load (a configuration of dots in a grid) or a verbal memory load (a list of letters). Both experiments showed that mental animation interferes more with memory for a concurrent visuospatial load than with memory for a verbal load. Experiment 1 also showed that a visuospatial working memory load interferes more with mental animation than does a verbal memory load. Furthermore, Experiment 2 showed that mental animation interferes more with a visuospatial memory load than does a verbal reasoning task that takes approximately the same amount of time.     

Sex differences in eavesdropping on nonverbal cues: Developmental changes.

Examined the developmental acquisition of females' superiority in decoding nonverbal cues. Three age groups (121 male and 129 female 9–15 yr olds, 46 male and 63 female high school students, and 32 male and 49 female undergraduates) were examined cross-sectionally, and 24 male and 24 female 11–24 yr olds were examined longitudinally. Decoding of 4 types of nonverbal cues (face, body, tone, and discrepancies), arranged from the most to the least controllable (most "leaky") channel, was examined. ANOVA and the appropriate contrast showed that as age increased, females lost more and more of their advantage for the more leaky or more covert channels but that they gained more and more of their advantage for the less leaky channels. Results of the longitudinal 1-yr study support those of the cross-sectional study—during the year, women lost more and more of their advantage in more leaky channels. Results are consistent with a socialization interpretation—that as females grow older, they may learn to be more nonverbally courteous or accommodating. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental changes in line bisection: A result of callosal maturation?

Normal adults tend to bisect horizontal lines to the left of the objective middle, especially when using the left hand. This bias has been attributed to the dominance of the right hemisphere in spatial attention. The authors investigated the effect of hand use and line position in visual line bisection in right-handed children and adults, classified into 4 different age groups: 10-12, 13-15, 18-21. and 24-53 years ( N = 98). All 4 groups showed the characteristic leftward bias when using the left hand. When using the right hand, the youngest group showed a rightward bias, whereas the other 3 groups all showed a leftward bias. This suggests a shift from contralateral to right-hemispheric control during puberty and may reflect maturation of the corpus callosum. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental changes in the understanding of pictorial representations of sound.

Two studies examined understanding of pictures representing sound production among 112 3–6 yr olds. In Study 1, Ss labeled pictures as either showing sound or not; in Study 2, Ss chose which of a pair of pictures showed sound. Pictures varied as to the extent the representations were designed to be analogous to actual sound production in the environment. Different types of pictorial representation of sound were not equivalent in their ability to evoke a correct interpretation. Ss across the age range tested all understood the pictures that depicted postures associated with sound production in the environment. Pictures that relied on conventional or arbitrary representations of sound, such as lines radiating from a mouth, were less well understood by the younger Ss. Over the preschool years, however, there was substantial improvement in Ss' skill at interpreting these pictures. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental changes in the effect of acidosis on contraction, intracellular pH, and calcium in the rabbit mesenteric small artery

The purpose of the present study was to determine developmental changes in the effect of respiratory acidosis on vascular smooth muscle contraction. Vessel diameter, intracellular pH (pHi), and calcium concentration ([Ca]i) were measured in a cannulated preparation of the small mesenteric artery of newborn and adult rabbits. In the artery precontracted by high KCl, acidosis caused a vasorelaxation both in the newborn and the adult; the vasorelaxation was greater in the newborn than in the adult. The fura-2 fluorescence ratio, an indicator of [Ca]i, decreased transiently during acidosis and the decrease was similar in the two age groups. In the artery precontracted by norepinephrine, acidosis caused a transient vasoconstriction in the adult and a vasorelaxation in the newborn. In these vessels, the fura-2 fluorescence ratio increased transiently during acidosis; the increase was similar in the two groups. Upon induction of acidosis, pHi fell rapidly in the artery precontracted by norepinephrine or high KCl, and the depression of pHi was similar in the two groups. In the skinned smooth muscle preparation, a tension-[Ca] relationship curve at pH 7.1 was not significantly different from that at pH 6.8 in the adult. In the newborn, the tension-[Ca] curve at pH 6.8 was shifted to the right, compared with that at pH 7.1. These data suggest that the vasorelaxant effect of respiratory acidosis in the premature vessel is greater than in the adult. The greater vasorelaxation in the newborn cannot be explained by the age-related difference in pHi or [Ca]i during acidosis. The greater sensitivity of myofibrils to low pHi in the newborn may, at least in part, be responsible for the greater vasorelaxation in this age group.