Estimation of interhemispheric dynamics from simple unimanual reaction time to extrafoveal stimuli

This essay reviews research on interhemispheric transfer time derived from simple unimanual reaction time to hemitachistoscopically presented visual stimuli. Part 1 reviews major theoretical themes including (a) the significance of the eccentricity effect on interhemispheric transfer time in the context of proposed underlying neurohistological constraints; (b) the significance of gender differences in interhemispheric transfer time and findings in dyslexics and left-handers in the context of a fetal brain testosterone model; and (c) the significance of complexity effects on interhemispheric transfer time in a context of dynamic vs. hard-wired concepts of the underlying interhemispheric communication systems. Part 2 consists of a meta-analysis of 49 published behavioral experiments, in view of drawing a portrait of the best set of experimental conditions apt to produce salient, reliable, and statistically significant measures of interhemispheric transfer time, namely (a) index rather than thumb response, (b) low rather than high target luminance, (c) short rather than prolonged target display, and (d) very eccentric rather than near-foveal stimulus location. Part 3 proposes a theoretical model of interhemispheric transfer time, postulating the measurable existence of fast and slow interhemispheric channels. The proposed mechanism's evolutionary adaptive value, the neurophysiological evidence in its support, and favorable functional evidence from studies of callosotomized patients are then presented followed by proposals for critical experimental tests of the model.     

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.     

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.     

PREDICTION OF THE FUTURE POSITION OF A MOVING OBJECT

B onnet , C. & K olehmainen , K. Prediction of the future position of a moving object. Scand. J. Psychol ., 1969, 10 , 6570.—Hypothesis: prediction of the reappearence of a moving object involves some kind of estimation of space, velocity, and time. Results: the performance depends on the relative ease of utilisation of those cues when all are available in the situation. Conclusion: no general rule can be applied to all situations, because different strategies are used in different situations. The parameter which carries most weight in any given situation is determined by the ease with which the relevant information can be extracted from that parameter, relative to the other two.     

A generalization of the principle of causality,which makes it applicable to evolutionary systems

The principle of causality has traditionally been formulated in terms of the dynamic equations of classical physics. It has been believed that only stable (conservative) systems can be meaningfully studied in this way. The evolutionary systems studied by social scientists and biologists are non-conservative, and so are excluded from the traditional formulation of causality. The author argues that causal laws for non-conservative systems can be meaningfully formulated. An example based on Malthus' population theory is given.     

A Follow-Up Study of Spring, 1966, High School Graduates in the State of Utah

This study presents some of the results of a study of youth potential and youth opportunity in the State of Utah. The findings suggest that the immediate post high school plans of high school seniors, when stated during the spring prior to graduation, are relatively accurate indicators of actual post high school activities, but plans stated during the preceding fall are relatively unrealistic; also unrealistic are estimates of years of college attendance by first-quarter freshmen. The findings also reveal that while practical considerations weigh most heavily in the choice of a college, colleges in Utah have images which likely influence prospective students' choices.