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Discrimination of visual stimuli representing prey versus non-prey by the praying mantis Sphodromantis lineola (Burr.).

Adult, female praying mantids, Sphodromantis lineola (Burr.), were presented with seventy, flat black rectangles which moved toward the mantids (in the horizontal plane) against a white background. The lengths of the lures' edges parallel to their direction of movement, 1(1), were 1.5, 3, 6, 12, 18, 24, 30, 54, 72, or 114 mm; the edge lengths perpendicular to movement direction, 1(2), were 1.5, 3, 6, 12, 18, 24, or 30 mm. Mantids emitted the most predatory behaviors to square lures (1[1] = 1[2]) for which 1(1, 2) = 3-12 mm, and to 'worm' lures (1[1] greater than 1[2]) for which 1(2) = 1.5-6 mm. 'Anti-worm' lures (1[1] less than 1[2]) were poor releasers of predatory behavior. These results reconcile seemingly discrepant findings between studies that have presented mantids with various types of oscillating, rotating and/or three-dimensional lures. Further, the results indicate that like other terrestrial predators, such as toads, prey recognition by S. lineola is approximate and based on the spatiotemporal relationships between the features of moving objects (i.e. worm versus anti-worm). These findings are congruent with data on mantid prey selection in the wild.

Animals↗

An electrophysiological study of the effects of orthographic neighborhood size on printed word perception.

In two experiments participants read words and pseudowords that belonged to either large or small lexical neighborhoods while event-related brain potentials (ERPs) were recorded from their scalps. In Experiment 1, participants made speeded lexical decisions to all items, while in Experiment 2 they engaged in a go/no-go semantic categorization task in which the critical items did not require an overt behavioral response. In both experiments, words and pseudowords produced a consistent pattern of ERP effects: items with many lexical neighbors (large neighborhoods) generated larger N400s than similar items with relatively fewer lexical neighbors (small neighborhoods). Reaction time (RT, Experiment 1), on the other hand, showed a different pattern consistent with previous behavioral studies. While words tended to produce a facilitation in RT for larger neighborhoods, pseudowords produced an inhibition effect. The findings are discussed in terms of recent theories of word recognition and the functional significance of the N400.

Adolescent↗

Perceptual deficit in schizophrenia: a defect in redundancy utilization, filtering or scanning?

The perception by schizophrenic patients of stimuli with more than one feature (dimension) was investigated using psychiatric and non-psychiatric control groups. Indices of the ability (a) to make use of redundant stimulus cues, (b) to 'screen out' or filter irrelevant stimulus features, and (c) to scan the perceptual field for relevant stimulus features, indicated that only filtering was consistently poor in schizophrenia. It has been suggested that the schizophrenic patient may tend to perceive his environment in an undifferentiated holistic manner rather than in an analytic manner and the implication for the theory of left hemisphere pathology in schizophrenia is discussed. However, the performance of the schizophrenic subjects did not differ significantly from that of the group of depressed patients, which suggests that the selective attention deficits previously observed in schizophrenia are not specific to the disorder.

Adult↗

Stimulus augmenting and field dependence in children of alcoholic fathers.

The relationship between paternal alcoholism and two perceptual characteristics, stimulus augmenting and field dependence, was tested in boys and girls aged 10-12. Thirty children of alcoholic fathers, presumed at high risk for the disease because of its familial-genetic component, were compared with 30 children of nonalcoholic parents. Stimulus augmenting was measured by the Kinesthetic Figural After-Effect (KFA) test and field dependence by the Embedded Figures Test (EFT). It was reasoned that the consistent findings of field dependence in alcoholics could be a manifestation of brain damage and the consequent cognitive deficits often found in alcoholics. Thus it was proposed that field dependence would not differentiate the children of alcoholic fathers from those of nonalcoholics. No difference in field dependence was found between the groups, which supports other evidence that alcoholism can lead to field dependence. Since KFA scores revealed a significantly higher incidence of stimulus augmenters in the children of alcoholic fathers, it is proposed that stimulus augmenting is premorbid to alcoholism. It remains unclear, however, whether this phenomenon is due to an environmental or genetic factor.

Alcoholism↗

Area of depictions versus insufficient transformations in volume judgments.

Two hypotheses about judgments of apparent volume of depicted objects were compared. One hypothesis was that the area of the depiction influences judgments. The alternative was that volume judgments are based on an incomplete transformation from the two-dimensional stimulus to the object "implied" by the drawing. 38 college undergraduates ranked 24 drawings of rectangular boxes according to apparent volume. Results strongly supported the incomplete transformation hypothesis.

Adult↗

Comparison is not just subtraction: effects of time- and space-order on subjective stimulus difference.

In five experiments, participants made comparative judgments of paired successive or simultaneous stimuli. Time- or space-order errors were obtained, which varied with the interstimulus interval (ISI) or stimulus duration, as well as with the stimulus level. The results, in terms of scaled subjective differences, are well described by Hellström's (1979) sensation-weighting model. With successive presentation, in comparisons of line length and tone loudness, the first stimulus had the greater weight in determining the subjective difference for short ISIs, the second for longer ISIs. In comparisons of duration (auditory and visual), the second stimulus had the greater weight. For simultaneously presented line lengths, the left stimulus had the greater weight.

Adult↗