Individual Differences in Infant Visual Attention: Four-Month-Olds' Discrimination and Generalization of Global and Local Stimulus Properties

Cognitive performance and development is negatively correlated with fixation duration patterns during infancy, and evidence suggests that long-looking infants may process visual information more slowly than short-looking infants. 3 experiments described here tested the possibility that these differences may be due to differential sensitivity to global and local visual information. Infants were administered discrimination and generalization tasks involving global and local information at varying levels of familiarization time. Results indicated that 4-month-olds process visual information in a global-to-local sequence. Both long- and short-looking infants were sensitive to both types of information, although long lookers required additional familiarization time to match the performance of short lookers. Finally, apparent "generalization" of global information at brief familiarization levels was traced to insensitivity to local stimulus properties. The results do not support the hypothesis that long- and short-looking infants are differentially sensitive to global versus local visual information at 4 months of age.     

Developmental changes in endogenous control of attention: the role of target familiarity on infants' distraction latency

This study evaluated the interactive effects of endogenous and exogenous influences on infants' attention allocation by assessing the role of target familiarity on distraction latency during object exploration. In Experiment 1 (N = 54), infants' distraction latencies as they investigated both familiar toys (ones they previously had seen in a familiarization procedure) and novel toys (ones they had not seen in the familiarization procedure) were assessed longitudinally at 6.5 and 9 months of age. In Experiment 2 (N = 32), infants' distraction latencies were assessed at either 6.5 or 10 months as they investigated either familiar or novel targets. In both experiments, older infants, but not younger infants, exhibited longer latencies as they investigated novel toys as compared with their latencies as they investigated familiar toys. These results are discussed in terms of developmental changes in the interactive effects of endogenous and exogenous factors controlling attention allocation.     

Noncontingent stimulation, stimulus familiarization, and subsequent learning in young infants

2 experiments assessed the effects of prior noncontingent or familiarization experience on subsequent operant conditioning (kick-produced mobile movement) in young infants. In Experiment 1, infants received either long- or short-term noncontingent exposure to their own rotating mobile or simply viewed this mobile for several days while it remained motionless. In Experiment 2, long-term exposure was provided by the same novel mobile used for subsequent training. In both experiments, prior noncontingent experience did not interfere with subsequent conditioning. In Experiment 2, however, simple long-term familiarization with the training mobile precluded "evidence" of learning. The results indicated that infants develop expectancies regarding how stimuli occurring in particular contexts should behave based on their prior experiences with these stimuli.     

Development of knowledge of visual-tactual affordances of substance

Infants of 12 months were familiarized in the dark with an object of either a hard or an elastic (spongy) substance. Following 60 sec of manipulation, a visual preference test was given with simultaneous presentation of 2 films of identical objects, 1 moving in a pattern characteristic of a rigid object and 1 moving in a pattern characteristic of an elastic object. Infants handled the 2 substances differently in an appropriate manner and looked preferentially with more and longer first looks to the type of substance familiarized. A replication of this experiment with familiarization in the light yielded comparable results. A third experiment with 1-month-old infants allowed them to mouth objects of either a hard or a soft substance for haptic familiarization and then tested looking preferences with real objects moving rigidly or deforming. These infants looked longer at the object moving in a manner characteristic of the novel substance. The results, together, suggest that quite young infants detect intermodal invariants specifying some substances and perceive the affordance of the substance.     

Information processing in seven-month-old infants as a function of risk status

7-month-old full-terms and high-risk preterms (less than 1,500 grams at birth) were compared on problems of visual recognition memory and tactual-to-visual cross-modal transfer. On the visual problems, preterm infants showed significantly less differential attentiveness to novelty than full-terms. They also required longer exposure times during visual familiarization, primarily because of longer pauses between fixations. Preterms and full-terms exhibited different patterns of looking, as indicated by the duration of fixation and the frequency in shifts of gaze. On the cross-modal problems, preterms and full-terms both exhibited similar and significant preferences for familiar rather than novel stimuli, a direction of preference which suggests that these problems were relatively difficult for both groups. For the preterms, novelty and exposure-time scores were found to be related to several medical risk factors. Novelty preferences were compromised in preterms who had suffered RDS postnatally, particularly those who had required prolonged mechanical ventilation. In general, high-risk preterms exhibited deficits in visual recognition memory and in the ability to recruit, sustain, and shift attention.     

Deficits in visual recognition in low birth weight infant pigtailed monkeys (Macaca nemestrina)

15 low birth weight and 15 normal birth weight pigtailed monkey infants were administered an adaptation of a standardized test of visual recognition memory, originally developed for human infants. Animals were given a series of problems in which 2 identical black-and-white patterns were presented for a familiarization period. The previously exposed pattern was then paired with a novel one, and looking time to each pattern was recorded. The normal birth weight animals directed a significant amount of their visual attention to the novel stimuli, thus demonstrating recognition abilities. As a group, the performance of the low birth weight infants remained at chance. These findings have important implications for an animal model to examine factors contributing to poor cognitive outcome in low birth weight human infants.     

Recognition of Moving and Static Faces by Young Infants

This study compared 3- to 4-month-olds' recognition of previously unfamiliar faces learned in a moving or a static condition. Infants in the moving condition showed successful recognition with only 30 s familiarization, even when different images of a face were used in the familiarization and test phase (Experiment 1). In contrast, infants in the static condition showed successful recognition only when the familiarization duration was lengthened to 90 s and when the same image was used between the familiarization and test phase (Experiments 2 and 3). Furthermore, presentation of multiple static images of a face did not yield the same level of performance as the moving condition (Experiment 4). These results suggest that facial motion promotes young infants' recognition of unfamiliar faces.     

Individual Differences in Infant Visual Attention: Are Short Lookers Faster Processors or Feature Processors?

Individual differences in the duration of infants' visual fixations are reliable and stable and have been linked to differential cognitive performance; short-looking infants typically perform better than long-looking infants. 4 experiments tested the possibility of whether short lookers' superiority on perceptual-cognitive tasks is attributable to attention to the featural details of visual stimuli, or simply to differences in the speed or efficiency of visual processing. To do this, the performance of long- and short-looking 4-month-olds was examined on separate discrimination tasks that could be solved only by processing either featural or global information. The global task was easier than the featural task, but as the amount of time allotted for infants to solve either type of task was decreased, short lookers' performance was superior to that of long lookers. These results thus lend support to a speed or efficiency of stimulus processing interpretation of infant fixation duration.     

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.     

Differential rates of visual information processing in full-term and preterm infants

This study investigated the effect of increasing familiarization time on the visual recognition memory of 6- and 12-month-old full-term and preterm infants. Infants were given trials in which they viewed a shape for either 10-, 15-, 20-, or 30-sec familiarization and were then tested for visual recognition memory using the paired comparison technique. While the older infants showed evidence of recognition memory after less familiarization time than the younger ones, at both ages preterms required considerably longer familiarization than full-terms. The pattern of performance replicates our earlier finding of developmental lags in the visual information processing of 6-month-old preterms and extends these findings to 12-month-olds. These results suggest that there are persistent differences between preterm and full-term infants throughout at least the first year of life in this very fundamental aspect of cognition.     

Predicting the outcomes of physical events: two-year-olds fail to reveal knowledge of solidity and support

Two-year-olds' (N = 153) knowledge of solidity was tested in four search tasks adapted from infant looking-time experiments. In Experiment 1, 2-year-olds failed to search in the correct location for a falling ball after a hidden shelf that blocked its trajectory had been inserted in the apparatus. Experiment 2 extended this finding by showing that 2-year-olds failed to take into account the effects of either removing or inserting a shelf in their search for a toy dropped behind a screen. Experiment 3 examined sensitivity to the constraint provided by a solid barrier on horizontal motion. In all three experiments, 2-year-old children searched initially at the location where they saw the object during familiarization. Experiment 4, using multiple test trials but no familiarization to a pretest location, also showed that 2-year-olds failed to take the presence or absence of a barrier into account when planning where to search for a toy they had seen dropped behind a screen. In all of these studies, 2-year-olds showed no evidence of representing solidity and support constraints on the trajectories of falling objects. Experiments 1 and 3 also included 2 1/2-year-olds (N = 31), who succeeded on these search tasks. The implications of the poor performance of 2-year-olds, in the face of success by very young infants on looking-time measures of sensitivity to similar constraints on object motion, are discussed.     

Infant visual attention in the paired-comparison paradigm: test-retest and attention-performance relations

The visual behavior of infants in the paired-comparison paradigm was assessed with multiple discrimination tasks week-to-week at 4 and 7 months and longitudinally from 4 to 7 months. Results indicated that although task-to-task reliability was extremely variable and typically low, most measures of infants' attention averaged across multiple tasks were reliable from 1 week to the next as well as relatively stable over the longer longitudinal period. Across all groups, infants who had shorter fixations (i.e., more fixations per fixed-exposure period) during the familiarization phase showed higher novelty preferences. While infants' shift rate during test phases was a reliable individual characteristic at 7 months, it was not at 4 months; rather, data suggested that the difficulty of the stimulus discrimination may be related to young infants' shift rate.     

Parsing Items into Separate Categories: Developmental Change in Infant Categorization

Three experiments report developmental change in infants' tendency to parse exemplars into separate categories. In Experiment 1, a familiarization-novelty preference procedure was used. Fifty-four 4-, 7-, and 10-month-old infants were familiarized with members of two basic-level animal categories (cats and horses) and tested with novel members of the familiarized categories and with members of a third category (dogs). In Experiment 2, a habituation-dishabituation procedure was used. Forty-eight 7- and 10-month-old infants were habituated to examples of both male and female faces and tested with novel gender-typical and gender-ambiguous faces. In both experiments, 10-month-old infants appeared to form differentiated categories, whereas younger infants formed a single category to include the range of items presented during familiarization. Experiment 3 ruled out a priori stimulus preferences as an explanation for the 10-month findings in Experiment 2.     

Infant Attention and Early Childhood Executive Function

Individual differences in infant attention are theorized to reflect the speed of information processing and are related to later cognitive abilities (i.e., memory, language, and intelligence). This study provides the first systematic longitudinal analysis of infant attention and early childhood executive function (EF; e.g., working memory, inhibitory control, cognitive flexibility). A group of 5‐month‐olds (n = 201) were classified as short or long lookers. At 24, 36, and 48 months of age, children completed age‐appropriate EF tasks. Infant short lookers (i.e., more efficient information processors) exhibited higher EF throughout early childhood as compared to infant long lookers, even after controlling for verbal ability (a potential indicator of intelligence). These findings are discussed in relation to the emergence of executive attention.     

Recall of three-item sequences by pigeons

Pigeons were trained to recall an arbitrary sequence on a delayed matching-to-successive-samples (DMTSS) task. Sample items were presented successively and then displayed simultaneously. Subjects were required to respond to them in the order in which they appeared. In Experiment 1, pigeons responded correctly on 75% of the trials on a two-item DMTSS task but at a chance level of accuracy on a three-item task. In Experiment 2, pigeons who learned to produce a three-item sequence prior to DMTSS training mastered a three-item DMTSS task at a 75% level of accuracy. Control groups, trained initially with the same items on nonserial tasks, performed as poorly on a three-item DMTSS task as the naive subjects of Experiment 1. It was hypothesized that pigeons that first learned to produce a three-item list were able to recall three-item samples in DMTSS because they had learned to represent three-item sequences.     

Same-different comparison of duration

Pigeons were trained on a task in which a red light of durationt ₁ was followed by a green light of durationt ₂ and then responses to different keys were reinforced according to whether the durations of the stimuli were the same or different. For Experiment 1, duration pairs consisted of all combinations of 1, 2, 4, and 8 sec. In Experiment 2,different-duration pairs included only combinations witht ₁ >t ₂ and, in addition, 2 subjects with extended training involving lesser-greater duration comparisons were transferred to the same-different task. Two of 3 subjects learned the task in Experiment 1 and analyses suggested that choices were based on specific instances, not on a temporal same-different rule. All 5 birds acquired the discrimination in Experiment 2, where it appeared that choices were controlled by a combination of relative and absolute rules. Accuracy decreased following transfer from a lesser-greater to a same-different discrimination, but performance was above chance on the first transfer session. In both experiments, however, accuracy was below that found in earlier work with lesser-greater comparisons of duration. These findings are discussed in relation to prior research with lesser-greater comparisons of duration and same-different tasks involving nontemporal stimuli.     

Contextual Constraints on Memory Retrieval at Six Months

In 3 experiments, 6-month-old infants learned to move a mobile by kicking and were tested 1 to 21 days later for retention of the newly acquired memory as a function of the training and testing contexts. In Experiment 1, decreasing the relative distinctiveness of the training and testing context did not impair retrieval of the newly acquired memory. In Experiment 2, however, testing in a different context completely eliminated retention after delays of 1 and 3 days, when retention was otherwise perfect; after progressively longer delays, retention improved paradoxically. The familiarity or novelty of the test context was not a factor in the failure of infants to recognize the mobile in the altered context after 1 day. In Experiment 3, the effect of an altered context was assessed in a reactivation paradigm. After the training memory was forgotten, infants were presented with the original mobile as a reminder and were tested for retention of the training memory 1 day later. When either the reminding context or the testing context was different, they exhibited no retention. These findings reveal that memory retrieval at 6 months is highly specific to the setting in which the memory is acquired. We propose that infants learn what specific events are associated with what specific places prior to the age when they can locomote independently and acquire a spatiotemporal map of the relations between those places.     

Perception of kinetic illusory contours by two-month-old infants

Perception of kinetic illusory contours by 2-month-old infants was explored with sparse random-dot displays depicting an illusory shape against a background. In Experiment 1, 24 infants were habituated to a shape specified by accretion and deletion of background texture and relative motion, and exhibited a novelty preference when presented with luminance-defined familiar and novel shapes. Subsequent experiments explored kinetic cues in isolation. In Experiment 2 (n = 24), relative motion information was removed, leaving accretion and deletion of texture and luminance cues, and in Experiment 3 (n = 24), only relative motion information was available. In both these experiments the novelty preference obtained in Experiment 1 was replicated. Results from a control condition (n = 12) mitigated against the likelihood of an inherent preference for either of the test shapes. These findings reveal an early capacity to perceive shape solely from kinetic information, and suggest a mechanism geared toward spatiotemporal boundary formation that is functional shortly after birth. Theories of development of edge and motion discrimination are discussed.     

Differential effects of omitting comparison stimuli on symbolic and identity matching to sample: Evidence for altered instructional processes in pigeon short-term memory

Two experiments were performed to determine the effects of omitting the comparison stimuli in a matching-to-sample task. In Experiment 1, birds were trained initially on both symbolic and identity matching to sample. Comparison stimuli were then omitted following the presentation of a particular sample stimulus, and this decreased the number of sample (observing) responses. The reintroduction of the comparison stimuli on subsequent probe trials revealed that the accuracy of symbolic matching was reduced to chance levels, while identity matching accuracy was significantly below chance. In Experiment 2, a similar procedure was employed; however, observing responses to the comparison-omitted samples were maintained by direct reinforcement (fixed ratio 20). Matching accuracy during probe trials was again at chance levels for symbolic matching but, contrary to Experiment 1, was significantly above chance for identity matching. The differential effects of omitting comparison stimuli on symbolic and identity matching trials in these two experiments were interpreted within a framework which assumes that instructional processes are altered by comparison-omission procedures.     

Visual and olfactory oddity learning in rats: What evidence is necessary to show conceptual behavior?

Experiment 1 involved the use of plastic and wooden objects and trial-unique problems. The rats performed successfully on nonconceptual oddity problems given before and after conceptual training, showing that the testing conditions were suitable, but they showed chance performances on the trial-unique problems. Experiment 2 involved the use of olfactory discriminanda. Five pretraining problems and 300 unique five-trial problems were presented. Two of 3 rats performed better than chance on Trial 2 and on Trials 3–5, but all performed at chance levels on Trial 1 throughout. The data suggest that the rats responded to specific odors on Trials 2–5 following the Trial 1 experience, as opposed to respondingconceptually to the “odd” odor. Had they responded conceptually to odd odors, they should have performed better than chance on Trial 1. These findings and the general logical argument that they support are considered in the context of the numerous inconclusive reports of the use of the oddity concept by nonprimate animals.