What happens between an external stimulus and an overt response?

Peripheral components of feedthrough loops were psychophysiologically measured from the brain, both forelimbs, the tongue and the eyes during simple and choice reaction time tasks using linguistic and non-linguistic stimuli. Closing a microswitch with the little finger was the overt response. Covert electromyographic (EMG) responses were computer identified in the following average temporal order: generally, the earliest covert reactions were in the tongue, brain, eyes, and passive arm-hand region. Next were complex EMG events in the active limb. These covert reactions may function in feedthrough loops to generate and transmit codes during internal information processing. The passive armhand responses occurred significantly earlier than the onset of the covert EMG burst for closing the microswitch; perhaps there is an inhibitory response “commanding” the passive arm not to respond, before the other (active) limb can overtly respond. Mean response patterns to linguistic and non-linguistic stimuli were almost identical. Reaction time to the onset of the EMG burst for switch closing was from 40 to 95 milliseconds earlier than the usual overt reaction time measure (that to switch closing), suggesting that reaction time studies might be improved by using the onset of EMG increase as the more sensitive and precise measure.     

Conservation of temporal information by perceptual systems

Experiments in the auditory, visual, and vibratory modality employed two brief discriminably different stimuli, which were presented with temporal asynchronies unequivocally below the Hirsh-Sherrick threshold for performing temporal order judgments. A pair of such stimuli, experienced as a unitary perceptual event, is referred to as a “micropattern” composed of two “stimulus elements.” Ss could readily distinguish between two such micropatterns in which the temporal order of the stimulus elements was reversed. The discrimination was based on the perceptual dominance of the second stimulus element of each micropattern. This perceptual dominance was studied as a function of stimulus-element onset and offset asynchrony, the duration and intensity of the stimulus elements, and the difference (in frequency or wavelength) between the stimulus elements of a micropattern. The results suggest the existence of an operation of all perceptual systems in the time domain that acts to conserve information concerning the temporal order of the two stimulus elements at the expense of discriminatory acuity of the f’~rst element.     

Effect of stimulus duration on perceptual onset and offset latencies

The effects of stimulus duration on perceptual onset and offset latency were compared in vision and audition. It was found that perceptual onset latency was independent of stimulus duration but that the perceptual offset latency was longer for brief stimuli than for stimuli that exceeded a critical duration. For stimuli longer than the critical duration, the perceptual onset and offset latencies were equal: The same temporal relationships were found in both modalities. The results indicate that for any specific stimulus parameters, reduction of stimulus duration results, ultimately, in a perception of fixed duration.     

Relationships among vocational training,income, and job complexity of high school dropouts and high school graduates

High school dropouts (N = 100) and high school graduates (N = 100), of which half of each group had received vocational training and the other half had not, were compared on data taken from the inactive employment applications of the Fort Walton Beach, Florida State Employment Office. The sample (N = 200) consisted of an equal number of males and females while 30% were minority group members. A two-way analysis of variance showed that completing vocational training was positively correlated with higher income and job complexity level. The existence or absence of vocational training was a more potent influence on income level and job complexity than was completion of high school.     

Visual detectability gradients: effect of illiteracy.

When subjects are required to detect a target pattern presented simultaneously with a number of similar non-target patterns in a brief exposure, marked differences of target detectability are observed as a function of the spatial location of the target (Efron, Yund, & Nichols, 1987, 1990a, b, c; Yund, Efron & Nichols, 1990a, b, c). These differences in detectability as a function of retinal locus, referred to collectively as a "detectability gradient," have been attributed to a central serial processing mechanism, which scans the decaying neural representation of the image. There also is evidence suggesting that, at least in some circumstances, this gradient may be influenced by the direction in which subjects normally read (Heron, 1957; Mishkin & Forgays, 1952; Efron et al., 1987). The object of the present experiment was to determine whether the detectability gradient obtained with the non-linguistic stimuli used in our previous experiments would differ as a function of previous reading experience. The experiment was performed on a group of 60 illiterate subjects and on a socioeconomic-matched group of 60 literate subjects. While the overall accuracy of target detection was identical in the two groups, there were significant differences between the detectability gradients of the literate and illiterate subjects. The nature of these differences indicates that reading, or learning to read, causes the scanning mechanisms of literate subjects to adopt more consistent scan paths, from subject to subject, than they would have adopted without this reading experience.