Five experiments were conducted to examine the performance of young infants on above versus below categorization tasks. Experiments 1 and 2 showed that infants did not form abstract categorical representations for above and below when familiarized with different objects depicted in a constant spatial relation relative to a horizontal bar and tested on a novel object depicted in the familiar and novel spatial relation. Experiments 3 through 5 examined perceptual‐attentional distraction versus conceptually based generalization explanations for young infant performance in the object‐variation version of the above‐below categorization task. Experiments 3 and 4 demonstrated that infants still did not form abstract categorical representations for above and below when object variation was removed from the familiarization trials or when object novelty was reduced during the preference test trials. However, Experiment 5 showed that 3‐ and 4‐month‐olds succeeded on the above versus below categorization task when familiarized with object variation and preference tested with a familiar versus novel object‐bar relation. These results indicate that young infants can form categorical representations for above and below in the object‐variation version of the above‐below categorization task, but that such representations are specific to the particular objects presented. Young infant performance in the object‐variation version of the above‐below categorization task thus reflects a conceptually based generalization limit rather than a problem of perceptual‐attentional distraction.

Visual field extent along the four diagonal meridia was measured cross-sectionally in 180 normal children (infants and toddlers), and 22 adults. Infants were tested monocularly at 3.5, 7, or 9 months, and toddlers were tested binocularly at 11, 17, or 30 months. Adult control data were obtained under monocular viewing. Three testing methods were investigated: static and hybrid static-kinetic perimetry, using LED arrays under computer control, and kinetic perimetry, using white styrofoam spheres manipulated by hand. Data analysis included corrections for false positives in the method of constant stimuli and for errors of anticipation in the ascending method of limits. Across all data sets from children, kinetic perimetry yielded larger, more adult-like fields, which approached adult levels around 17 months, whereas static and hybrid static-kinetic perimetry yielded smaller visual fields, approaching adult levels only at 30 months.

Influences on the development of perceptual categorization were examined by comparing the performance of three groups of infants on spatial and object categorization tasks. The groups consisted of 1) fullterm infants tested at 3 to 4 months of age, 2) healthy preterm infants tested 3 to 4 months from birth (postnatals), and 3) healthy preterm infants tested 3 to 4 months from their due date (postterms). Four experiments showed that fullterms and postterms outperformed postnatals on a spatial categorization task (i.e., 'above' vs. 'below', and that fullterms outperformed both postnatals and postterms on object categorization tasks (i.e., dogs vs. cats, and cats vs. birds). These results suggest that maturation may be the predominant influence on the early development of the ability to form categorical representations of spatial information, while preterm birth may exert a limiting influence on the development of object categorization abilities.

The present study investigated whether children would exhibit the weapon focus effect that has been demonstrated with adult eyewitnesses. Participants (4-and 5-year-olds, 7-and 8-year-olds, and adults) watched a videotape in which a target individual portraying one of two schema roles and holding either a weapon or a neutral object steals some money. Witnesses of all ages described the target's physical appearance less accurately if the target held an object that was inconsistent rather than consistent with his schema role. Additionally, there were age effects for both accuracy and amount of information reported. The results indicate that the weapon focus effect generalizes to child witnesses and that it probably occurs because weapons are inconsistent with an activated schema.

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