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Comparative aerial and underwater visual acuity of the mink, Mustela vison schreber, as a function of discrimination distance and stimulus luminance.

The aerial threshold visual angle of mink rose from 15.4 min at 10 cm stimulus distance to 19.1 min at 90 cm and the underwater angle varied from 32.7 min at 10 cm to 46.6 min at 90 cm, all at 34 mL luminance. At constant 30 cm stimulus distance, the aerial angle rose from 15 min at 34 mL to 51.7 min at 0.012 mL, the underwater angle from 31.4 min at 34 mL to 95 min at 0.012 mL, the aerial and underwater data forming similar curves. If mink hunt in water at somewhat higher light levels than in air they can obtain equal acuities in the two media.

Adaptation, Ocular↗

Orienting behaviour during aerial and underwater visual discrimination by the mink (Mustela vison schreber).

Orienting responses by mink during aerial and underwater visual discrimination tests were most frequent when the grating lines subtended angles at the eye near the visual threshold angle. Factorial analysis showed that in air and in water at ranges from 10 to 90 cm most responses occurred at 30 cm discrimination distance and more occurred to marginally supra-threshold than to marginally sub-threshold stimuli. Between media, more responses occurred in air than in water. At longer ranges the mink oriented less readily than at 30 cm but if orienting occurred better discrimination followed than if the mink did not orient.

Animals↗

The effects of viewing distance on fear of snakes.

Phobic subjects made magnitude estimations of the intensity of fear felt when viewing a snake at distances from 2.5 to 15.0 ft. Heart rate, skin conductance, and respiration were also measured throughout each 20 sec viewing period. A control group of nonphobic subjects made magnitude estimates of perceived nearness for the empty Plexiglas snake box at the same test distances. Judged fear was inversely proportional to distance. Thus, the fear-distance relation obeys Stevens' psychophysical power law with an exponent of -1.0. Examination of previous studies reporting such a finding revealed systematic departures from a power relation similar in form to the results of the perceived nearness control group, and to the expected outcome when category judgements of fear are made instead of magnitude estimates. The physiological measures varied in outcome. Measures of respiration showed no reliable effects. But heart rate and skin conductance decreased significantly for phobics as viewing distance increased.

Adolescent↗

Use of psychophysical scaling procedures in the assessment of phobias: a case example.

This paper reports on the utility of a psychophysical scaling procedure (magnitude estimation) for the measurement of treatment effectiveness among phobics. Pre- and post-treatment heart rate and magnitude estimates of fear in a snake phobic subject were examined. Magnitude estimates and heart rate both revealed treatment effects. The results suggest that magnitude estimates may be a more sensitive measure of fear. The usefulness of magnitude estimates as an assessment strategy is discussed.

Adolescent↗

Proximal spacing to facial affect expressions in schizophrenia.

Schizophrenics (N = 40), depressives (N = 36), anxiety neurotics (N = 35), and nonpatient controls (N = 60) were asked to walk forward from a distance of 10 feet to a distance comfortable for possible interaction with facial expressions of six affects and a neutral state, depicted in life-sized images. Schizophrenics demanded significantly greater proximal space than other groups to interact with facial affect expressions, especially the nonaroused ones (happy, sad, neutral state). Multiple discriminant analysis of the "comfortable interaction distance" data revealed that schizophrenic persons may be discriminated with moderate accuracy (52.5%) from other groups.

Adult↗

Children and adults' distance estimations in a large-scale environment: effects of time and clutter.

In two experiments adults (mean age = 19-5), sixth graders (mean age = 11-8), fourth graders (mean age = 9-8), and second graders (mean age = 7-8) walked a straight line distance through a large-scale environment. Subjects were then asked to estimate the time taken to traverse each half of the walk and to estimate the distance between objects seen along the walk. In Experiment 1 each half of the walk was traversed in the same amount of time but contained a different number of objects (clutter). Time and distance estimates were related, but were not affected by the number of intervening objects encountered between locations. In Experiment 2 subjects again encountered a different number of objects along each half of the walk but each half was traversed in varying amounts of time. Again, time and distance estimates were related, and there was no clutter effect. There were no consistent developmental differences across the two experiments. It was concluded that (1) Thorndyke's clutter effect does not occur across all types of spatial cognition tasks, and (2) children and adults tend to relate time and distance across a variety of distance estimation tasks.

Adolescent↗

Spatial cognition: gathering strategies used by preschool children.

How preschool children retrieve hidden objects was examined in two cross-sectional studies. The first was a simple task in which 1- and 3-year-olds saw two treats hidden in their living room. The newly walking infants generally sought the closer treat first, providing evidence for a least-distance spatial strategy. However, this strategy was affected by a tendency to approach the hiding place most recently baited. Three-year-old children used a least-distance strategy regardless of the order of hidings. In Experiment 2, 3- and 5-year-olds saw 12 puzzle pieces hidden in various containers equally spaced within a naturally furnished children's laboratory. Factors in addition to age were the distinctiveness of the containers and a requirement to return to the center of the array after each retrieval. Overall, children of both age groups were quite successful at this task, retrieving 11 of the pieces. However, 3-year-olds were less efficient, retrieving fewer pieces and requiring more searches. Detailed analyses of errors and patterns of choices indicated differential processes in achieving their performance. Three-year-old children showed the use of memories for events, discrimination of classes of hiding places, and efficient spatial biases. Five-year-old children were more likely to exhibit these processes concurrently.

Child Behavior↗