Individual and Developmental Differences in Disengagement of Fixation in Early Infancy

The current study investigated whether individual and developmental differences in look duration are correlated with the latency for infants to disengage fixation from a visual stimulus. Ninety-four infants (52 3-month-olds, 42 4-month-olds) were tested in a procedure that measured ocular reaction time to shift fixation from a central target to a peripheral target under conditions in which the central-target either remained present ("competition" condition) or was removed from the display ("noncompetition" condition). Look duration was correlated with disengagement latency; longer-looking infants were slower than shorter-looking infants to shift fixation to the peripheral target on competition trials, but not noncompetition trials. Results were similar for 3- and 4-month-olds, although 3-month-olds showed slower latencies on all trials. Furthermore, long-looking infants were not consistently slower, but rather showed greater variability in their response latencies under conditions that required disengagement of fixation. The results support the position that developmental and individual differences in look duration are linked to the development of the neural attentional systems that control the ability to disengage, or inhibit, visual fixation.     

Extended visual fixation and distractibility in children from six to twenty-four months of age

Distractibility during extended visual fixations in children 6 months to 2 years of age was examined. A children's Sesame Street movie (Follow That Bird) was presented to children (N = 40) for a minimum of 20 min while fixation was videotaped and heart rate was recorded. Distractors (computer-generated patterns or another Sesame Street movie) were presented on an adjacent television screen. Consistent with prior research with older preschool-age children, the latency to turn toward the distractor was a function of the length of the look occurring before distractor onset. For the period immediately before distractor onset, children had a greater sustained lowered heart rate for the trials on which they continued looking at the center television monitor than for the trials on which they looked toward the distractor. This pattern of distractibility suggests attention increases over the course of a look toward the television, and that heart rate changes reflect this increase in attention.     

Differential effects of a retention interval on latent inhibition and the habituation of an orienting response

In Experiment 1, rats experienced presentations of a discrete visual stimulus (Stage 1) until habituation of the orienting response (OR) occurred. On a test session given after an interval of 16 days (Stage 2) the OR reappeared. For control subjects that received no Stage 1 training but presentations of the light in Stage 2, habituation persisted during the test. All subjects then received conditioning trials on which the light preceded the delivery of food. They showed latent inhibition, acquiring the conditioned response less readily than control subjects that had not previously experienced the light. Experiment 2 confirmed that the latent inhibition effect survived the retention interval for subjects that received no habituation test session. This pattern of results implies that habituation of the OR and latent inhibition are determined by different mechanisms.     

Infant visual sustained attention and respiratory sinus arrhythmia

Infants were studied cross-sectionally at 14, 20, and 26 weeks of age. They were presented with varying and complex patterns on a TV screen. Two-thirds of the presentations were accompanied by an "interrupting stimulus" in the periphery delayed in time from the onset of fixation on the central stimulus. The infants were not easily distracted from looking at the central stimulus when the presentation of the interrupting stimulus occurred at the point of maximal heart rate (HR) deceleration. However, if the presentation occurred at the end of the HR response, the infants were easily distracted. Infants with large amounts of respiratory sinus arrhythmia (RSA; i.e., HR variability) in a baseline recording were less distractible during the deceleration-defined trials than were infants with low amounts of RSA. High-RSA infants also showed larger HR deceleration on these trials than did the low-RSA infants. These results are consistent with a model positing that sustained HR lowering during visual fixation is an index of active attention and that RSA is an index of voluntary, sustained attention in infants.     

Visual Attention Movements: A Developmental Study

The pattern of attention movements underlying reorientation of visual selective attention independent of eye movements was studied developmentally in 2 experiments. In Experiment 1, 8-year-old, 11-year-old, and college-age subjects first oriented their attention to a central location and were then cued to direct their attention either to the left or the right peripheral field. Following variable intervals, the target appeared at the cued location and reaction times were recorded. The data were interpretable in terms of the attentional spotlight theory since there was an interaction between distance of the target from fixation and SOA. In terms of this theory, the data indicate that the velocity of attention movements increases throughout the age range studied. Experiment 2, in contradiction to attentional spotlight theory, failed to find evidence of an interaction between distance and SOA. This experiment suggested that young children can covertly orient their attention by including valid, neutral, and invalid cues, and that these cues can both facilitate and inhibit attentional orientation. This experiment also extended the findings to central as well as peripheral cues.     

Serial habituation in two-, three-, and four-month-old infants.

Serial habituation of visual fixations in 2-, 3-, and 4-month-old infants was investigated through a design permitting cross-sectional, within-subject longitudinal, cohort longitudinal, and time-lag analyses. The components of the standard stimulus were displayed individually before and after successive exposures of the standard for familiarization. Relative saliencies of the components for each child were indexed by magnitude of responding to these parts in the initial presentation. Comparisons of the pre- and postexposure fixation times suggest that for all ages habituation was under way to the parts of the stimulus in orders of the relative saliencies. The nature of the data in general did not appear to be influenced significantly by any 1 methodology.     

Two- to eight-month-old infants' perception of dynamic auditory-visual spatial colocation

From birth, infants detect associations between the locations of static visual objects and sounds they emit, but there is limited evidence regarding their sensitivity to the dynamic equivalent when a sound-emitting object moves. In 4 experiments involving thirty-six 2-month-olds, forty-eight 5-month-olds, and forty-eight 8-month-olds, we investigated infants' ability to process this form of spatial colocation. Whereas there was no evidence of spontaneous sensitivity, all age groups detected a dynamic colocation during habituation and looked longer at test trials in which sound and sight were dislocated. Only 2-month-olds showed clear sensitivity to the dislocation relation, although 8-month-olds did so following additional habituation. These results are discussed relative to the intersensory redundancy hypothesis and work suggesting increasing specificity in processing with age.     

The stability of visual habituation during the first year of life

The short-term reliability and long-term stability of visual habituation and dishabituation in infancy were assessed in a sample of 186 infants from 4 age groups (3-, 4-, 7-, and 9-month-olds) seen for 2 within-age sessions and in a sample of 69 infants seen longitudinally at 3, 4, 7, and 9 months of age. Moderate week-to-week reliability (r's = .30-.50) was observed for duration-based and magnitude of habituation variables at all ages, although better reliability was evident at 4 and 9 months than at 3 and 7 months. In most cases, the reliability of habituation magnitude measures was attributable to the reliability of the peak fixation alone. Data from the longitudinal sample suggested that only the duration of peak fixation was consistently stable across the ages tested, although stability for several measures emerged across the 7-9-month testing. No consistent reliability or stability emerged for the presence or magnitude of dishabituation in either sample.     

Negative priming and occasion setting in an appetitive Pavlovian procedure

Rats received training in which two auditory target stimuli, X and Y, were signaled by two visual stimuli, A and B, and followed by food (i.e., A-->X+, B-->Y+). The test consisted of presentations of X and Y preceded either by the same signal as during training (same trials: A-->X, B-->Y) or by the alternative signal (different trials: A-->Y, B-->X). After 8 training sessions, the animals responded less on same trials than on different trials; this effect was significantly reduced after 24 training sessions. In two additional experiments, animals that had also experienced presentations of A and B alone, either before or during training, showed the opposite pattern of results, responding more on same trials than on different trials. These results are interpreted as being due to the interaction between the effects of occasion setting and negative priming (see Wagner, 1981).     

Eye movements of stumptailed monkeys during discrimination learning: VTE revisited

Eye movements of stumptailed monkeys were measured during learning of a pattern discrimination problem. Amount of scanning (shifts in visual fixation from one pattern to the other) increased once learning began and reached a maximum either at about the point that frequency of correct responses reached asymptote or just after that. These results, taken together with earlier findings on vicarious trial and error and operant observing behavior, suggest that this is the characteristic pattern of change in frequency of observing during visual discrimination learning. A change in information processing strategy is proposed as one explanation for these results. Duration of the last fixation on a discriminative stimulus during a trial showed similar, though not identical, changes with practice. The decrease in duration of the last fixation following learning contrasts with results of prior studies involving more complex tasks, and supports our conclusion that the duration of the last fixation is particularly sensitive to the cognitive processing requirements of the discriminative task.     

Infant habituation: assessments of individual differences and short-term reliability at five months

This study is concerned with individual differences and short-term reliability of infant-control habituation of visual attention. Habituation to single female faces and to single geometric patterns was observed separately in 2 groups of comparable 5-month-olds. Each group participated in habituation twice, and habituation sessions for each were separated from one another by 10 days. Across the 2 conditions, habituation was found to be distributed into 3 patterns: Most infants decreased looking and achieved criterion in a negatively exponential fashion, some infants first increased looking and then rapidly habituated, and some infants showed fluctuating and idiosyncratic looking-time functions prior to habituating. Both qualitative patterns and quantitative indexes of habituation showed moderate but significant reliability between assessment sessions. Quantitative and psychometric characteristics of habituation and the meaningfulness of habituation of attention as an index of infant cognition are discussed.     

Concept acquisition in the human infant.

The ability of 18-, 24-, and 30-week-old infants to learn conceptual categories regarding adult female faces was examined using a habituation paradigm. Little evidence for conceptual categorization occurred at 18 or 24 weeks, but at 30 weeks infants learned to respond to "a specific female face regardless of orientation" and to "female faces in general."     

Habituation and dishabituation of rats’ exploration of a novel environment

The habituation of locomotor activity across repeated exposures to a novel maze was studied in a series of experiments using rats as subjects. Habituation, defined as a decrease in ambulation, was greater on a second trial occurring 5 min after a first trial than on one occurring 60 min after. This short-term decrement occurred only when the same maze was used on both trials, and could be dishabituated by intertriai detention in another novel environment. On a delayed test trial, habituation was, in one case, somewhat greater following initial spaced trials, and in another condition, comparable following both massed and spaced trials. The longer term habituation was maze specific, but was not affected by the presence of a dishabituator following either or both of the first two trials. The results were discussed in terms of theories of “priming” and encoding variability.     

Latent habituation of the orienting response in the preweanling rat

The effect of inhibiting the orienting response on information processing was examined in four experiments. A nonsignal auditory stimulus was presented four times to preweanhng rats either 30 sec or 15 min after they had been placed in an unfamiliar environment (Experiments 1A and 2), shocked (Experiment 1B)5 or experienced a shift in environmental context (Experiment 1C). Both an autonomic (heart rate) and a behavioral componentx of the orienting response to the novel stimulus were recorded. In the 15-min condition, the auditory stimulus elicited a consistent orienting response on the first trial that habituated rapidly with successive trials. In contrast, the auditory stimulus did not elicit a detectable orienting response in the 30-sec condition on any of the four trials. However, when the auditory stimulus was re-presented after a brief retention interval, a comparable level of habituation was seen in both groups. These results demonstrate that animals in the 30-sec condition detected, attended to, and encoded the auditory stimulus even though they did not orient, either autonomically or behaviorally, to that stimulus when it was first presented. This process of response-independent habituation is best described as latent habituation. Like latent learning, latent habituation took place in the absence of any observable change in behavior. The implications of this effect for current theories of habituation and of the orienting response are discussed.     

Pigeons’ memory for event duration: Differences between visual and auditory signals

In Experiment 1, pigeons were trained to discriminate short (2 sec) and long (8 sec) durations of tone by responding to red and green comparison stimuli. During delay testing, a systematic response bias to the comparison stimulus correct for the long duration occurred. Tests of responding without the tone reduced accuracy on long-sample trials but not on short-sample trials suggesting that the pigeons were attending to the tone and not simply timing the total trial duration. The pigeons were then trained to match short (2 sec) and long (8 sec) durations of light to blue/yellow comparisons. During delay testing, “choose-long errors” occurred following tone durations, but “choose-short errors” occurred following light durations. In Experiment 2, accuracy was assessed on test trials in which the tone and the light signals were simultaneously presented for the same duration or for different durations. Pigeons responded accurately to durations of light, but were unable to accurately respond to durations of tone simultaneously presented with the light. The data from Experiment 1 suggest that there are important differences between light and tone signals with respect to the events that control the termination of timing. The data from Experiment 2 indicate that pigeons cannot simultaneously time visual and auditory signals independently and without interference. Consequently, they are inconsistent with the idea that there is a single internal clock that times both tone and light durations.     

Habituation of two response systems in the lizard,Anolis carolinensis

These experiments investigated habituation of two responses in the lizardAnolis carolinensis. In Experiment 1, intertrial intervals (ITI) of 5, 30, and 120 sec had various effects on habituation of dewlap distension and optokinetic response (OKR). Although there were no size differences noted for the OKR, smaller anoles (50–58 mm snout-vent length, SVL) failed to habituate under the 30- and 120-sec ITI of the dewlap response, while larger anoles (? 59-mm SVL) habituated under each ITI tested, with no response level differences between ITIs. Rates of habituation were similar within and across responses. In a second experiment, larger anoles were employed to study recovery and retention of dewlap distension and OKR habituation after 15-min and 24-h intervals. Complete recovery of both responses occurred in 24 h, with substantial recovery of both responses after 15 min. Retention was present for both responses after 15 min but not after 24 h. A multiple response-system approach is offered as a promising method for research and theories in habituation. Rather than concentrating upon a single response in one or more species, a multiple response-system approach examines similarities and differences in the habituation of various responses within a single species.     

Infant temperament and subject loss due to crying during operant conditioning

Infants who failed to complete a 2-day operant-conditioning task were compared with a stratified random sample of those who did on measures of infant temperament and several demographic characteristics. A discriminant-function analysis revealed that female infants who cried differed from female infants who did not cry on measures of duration of orienting and latency to approach sudden or novel stimuli. Reliable prediction of crying and noncrying could not, however, be made for males. No sex differences emerged in the incidence of crying or in the number of sessions completed. Partially successful females (i.e., those completing 1 of the 2 sessions) could reliably be discriminated from those who cried during the first session on measures of age at testing and maternal ratings of smiling behavior. The results of this study suggest that, as with habituation studies, subject loss in operant-conditioning studies is influenced by individual differences among the infants which may or may not adversely affect external validity.     

Perpetrators and context of child sexual abuse in Kenya

Child sexual abuse (CSA) interventions draw from a better understanding of the context of CSA. A survey on violence before age 18 was conducted among respondents aged 13–17 and 18–24 years. Among females (13–17), the key perpetrators of unwanted sexual touching (UST) were friends/classmates (27.0%) and among males, intimate partners (IP) (35.9%). The first incident of UST among females occurred while traveling on foot (33.0%) and among males, in the respondent's home (29.1%). Among females (13–17), the key perpetrators of unwanted attempted sex (UAS) were relatives (28.9%) and among males, friends/classmates (31.0%). Among females, UAS occurred mainly while traveling on foot (42.2%) and among males, in school (40.8%). Among females and males (18–24 years), the main perpetrators of UST were IP (32.1% and 43.9%) and the first incident occurred mainly in school (24.9% and 26.0%), respectively. The main perpetrators of UAS among females and males (18–24 years) were IP (33.3% and 40.6%, respectively). Among females, UAS occurred while traveling on foot (32.7%), and among males, in the respondent's home (38.8%); UAS occurred mostly in the evening (females 60.7%; males 41.4%) or afternoon (females 27.8%; males 37.9%). Among females (18–24 years), the main perpetrators of pressured/forced sex were IP and the first incidents occurred in the perpetrator's home. Prevention interventions need to consider perpetrators and context of CSA to increase their effectiveness. In Kenya, effective CSA prevention interventions that target intimate relationships among young people, the home and school settings are needed.     

Visual discrimination learning in the fire-bellied toad Bombina orientalis

This study explored the visual discrimination learning ability of fire-bellied toads (Bombina orientalis). Two groups of toads were trained in a simultaneous visual discrimination task involving video footage of either black crickets on a white background (black-cricket toads) or white crickets on a black background (white-cricket toads). Fifteen widely spaced acquisition trials were followed by 12 reversal trials. Successful learning was observed by decreased incorrect snapping and reduced latency to snap at the correct stimulus (S+) during acquisition; however, white-cricket toads executed significantly more incorrect snaps than did black-cricket toads. Both groups of toads could master the reversal task as measured by latency to snap at S+, but not as measured by the proportion of incorrect snaps. Despite the stronger potency of the black-cricket stimulus, the results showed that toads can learn a simultaneous discrimination task and a reversal of its contingency. This elaborate form of learning appears to be conserved among vertebrates.