Movement detection thresholds and stimulus duration

Movement detection thresholds were measured for varying exposures of a moving spot. A tradeoff was found in which an increase in duration (T) was offset by a decrease in the velocity required for detection (V). In the range of durations studied (about 50–700 msec), V × T was constant. The V × T constancy was interpreted in terms of the direct detection of movement as motion, and a comparison was made with Bloch’s law.     

Apparent size and duration of a movement after-effect

Four experiments were performed to study the relationship between Emmert's law and the duration of the movement after-effect (MAE). The duration of the MAE increased with increased distance of the test field; this result was shown to be produced by the correlative change in apparent size of the after image. The effect did not occur when cues for distance judgments were reduced. Reducing the duration of the MAE suppressed the variation in its duration at varying distances of the test field. Some implications for the mechanism of the MAE are discussed.     

Trait attributions and defense against insult from a dissimilar other

It was hypothesized that subjects would prefer to blame a character assault on negative ability characteristics of a dissimilar attacker as opposed to negative motivational characteristics in order to escape responsibility for the attack. It was reasoned that because we generally think of ourselves as having less potential influence over the abilities as opposed to the motivations of another person, it might be possible to diminish one's responsibility for another's behavior by attributing that behavior to that person's ability characteristics. Subjects in this experiment responded either to an insulting or noninsulting stimulus person who was either similar or dissimilar by selecting from a list of both motivational and ability bipolar trait dimensions, those dimensions they would most prefer to use in rating the stimulus person. As predicted, subjects responding to an insulting and dissimilar stimulus person showed a significantly greater preference for ability trait dimensions than subjects in the other conditions combined and also disliked the stimulus person more. The significance of these results for defensive attribution processes and phenomena such as racism and sexism are discussed.     

Phases in Movement After-Effects and their relationship to the kinetic figural effect

Summary A Movement After-Effect (MAE) observed on a structured test figure contains generally two successive phases. The initial one is non-contingent upon the test figure and is assumed to result from an adaptation process. The second phase is shown to be contingent upon the features of the test figure and their similarity with those of the generating figure. A conditioning process is assumed to share in its appearance. In Experiment I, it is shown that the areal spread of MAE which may appear in the contingent phase is likely to result from a generalization process in which part of the test figure corresponding to an unstimulated area becomes transiently effective in generating a MAE. In Experiment II distributed practice of the MAE is shown to lead to an increase in the duration of the effect when the generating and test figures are similar. This last result suggests that the true conditioning stimulus is the generating figure as such.     

A measurement technique for stability as applied in rifle shooting

A technique is described for the measurement, in the field, of stability and steadiness. Apparatus and method are provided along with suggested scoring procedures.     

Atypical Hemispheric Specialization in Intellectual Deficiency

In order to determine the relation between hemispheric specialization for language and intellectual deficiency, two groups of lower-IQ subjects were compared to normal-IQ controls on word-dichotic listening tasks. Two conditions in which stimuli differed by their level of phonological complexity were used. Normal controls showed the expected right-ear advantage in both conditions. Moreover, they showed a greater magnitude of ear difference on the condition requiring higher-order phonological processing. In the mentally deficient group, almost half the subjects exhibited a left-ear advantage and they showed no difference between the two conditions in terms of the magnitude of ear difference. These results point to the presence of atypical hemispheric specialization in mentally deficient subjects.     

Illusory form with inducers of opposite contrast polarity: Evidence for multistage integration

The perception of brightness differences in Ehrenstein figures and of illusory contours in phaseshifted line gratings was investigated as a function of the contrast polarity of the inducing elements. We presented either continuous lines or line-like arrangements composed of aligned dashes or dots whose spacing was varied. Ayes/no procedure was used in which naive observers had to decide whether or not they perceived a brightness difference in a given Ehrenstein figure or an illusory contour in a phase-shifted line grating. The results show that brightness differences are perceived to some extent in Ehrenstein figures with inducers of opposite polarity of contrast; however, the percentage ofyes responses was systematically lower and response times were longer than for figures with inducers of the same polarity. Phase-shifted line gratings with lines of opposite polarity of contrast yielded stronger illusory contours and shorter response times than those with lines of the same polarity. When the sign of contrast was not the same within a given line of induction, neither differences in brightness nor illusory contours were perceived. The results suggest that the mechanisms that lead to apparent differences in brightness are more sensitive to input of the same contrast polarity, the mechanisms generating illusory contours more sensitive to input of opposite polarity. The data are discussed in the light of a multistage approach to illusory form perception and some implications for cortical models of illusory contour integration are discussed.     

Signal clustering modulates auditory cortical activity in humans

Auditory streaming and its relevance to attentional processing was examined using event-related brain potentials (ERPs) in situations facilitating perception of one or two streams of sounds. Subjects listened to sequences of brief tones of three different frequencies presented in random order. In evenly spaced (ES) conditions, the three frequencies were equidistant on the musical scale. In clustered, easy (CE) conditions, the attended frequency was distinct, while the middle and extreme distractor tones were clustered together. In clustered, hard (CH) conditions, the attended frequency was clustered with one of the distractors. The subjects pressed a button in response to occasional target tones of longer duration at a prespecified frequency. The subjects were faster and more accurate in CE conditions than they were in ES conditions, and ERP attention effects were enhanced in amplitude in CE conditions. Conversely, the subjects were slower and less accurate in CH conditions and ERP attention effects were delayed in latency and decreased in amplitude. Clustering effects suggest that the processing of stimuli belonging to the attended stream was promoted and the processing of those falling outside the stream was inhibited. The timing and scalp distribution of clustering-related changes in ERPs suggest that clustering modulates early sensory processing in auditory cortex.