Glenn R. Hawkes

MASKING OF CUTANEOUS SENSATIONS IN MULTIPLE STIMULUS PRESENTATIONS.

Ten Ss made absolute judgments of electrocutaneous stimuli consisting of from one to three simultaneous stimulations of six loci. There were three loci in symmetrical positions on either side of Ss body—one on each shoulder blade, one on each arm between the elbow and the shoulder, and one on each side of the body just above the belt line. Each S responded with one of two response alphabets during 11 sessions of 41 trials each, over a period of three days. Differences between the two response alphabets were not significant, and neither were differences attributable to the interaction of the response alphabets with the number of loci stimulated. Increases in the percentages of erroneous responses with increases in the number of loci stimulated were both large and statistically significant; these increases were interpreted as evidence of a central mechanism of cutaneous masking.

Vigilance Effects for Duration Judgments with Two Levels of Task Demand

Vigilance effects were investigated with a duration judgment task, with or without a requirement also to perform mental arithmetic problems. Judged duration values were larger when only vigilance was performed; addition of the arithmetic task served to improve efficiency. Habituation processes thus are involved in a wide variety of behaviors.

Vigilance for Cutaneous and Auditory Stimuli as a Function of Intersignal Interval and Signal Strength

Abstract : Vigilance for infrequent auditory or electrical cutaneous stimuli at both weak and moderate intensities was investigated. Detection probability was very high for moderate intensity signals and weak auditory stimuli. Errors significantly increased with time on task for faint cutaneous signals. Increase of the intersignal interval significantly increased the number of errors. An explanation of the results is suggested in terms of greater habituation for weak or relatively infrequent signals.

Detection of Differences in Duration of Acoustic and Electrical Cutaneous Stimuli in a Vigilance Task

Abstract : The relative efficiency was determined of detection of changes in duration of moderately intense auditory, cutaneous, mixed auditory and cutaneous, and simultaneous auditory and cutaneous stimuli. Detection of differences in cutaneous stimuli were appreciably less efficient than detection of differences in auditory stimuli. Detection of simultaneous auditory-cutaneous signals was similar to that for auditory signals alone. Detection of auditory and cutaneous signals in the mixed conditions was similar to detection of such signals presented separately. There was some evidence for adaptation or habituation to cutaneous stimulation. When detection of differences in stimuli is employed as a basis for responding, the auditory modality should be employed rather than the cutaneous modality when possible. The generality of this finding should be explored by experiments involving other discriminations, different presentation rates of relevant and irrelevant signals, and different task durations.

Auditory Intensity Discrimination as a Function of Stimulus Presentation Method

Relative differential intensive limens were obtained at three frequencies and two intensities for three stimulus patterns involving fluctuation of a steady tone and three patterns involving separate stimuli. The same observers were utilized in all cases; in Experiment I, signals were presented through earphones. Somewhat lower thresholds were obtained for fluctuating intensity patterns than for separate stimuli patterns, thresholds tended to be lower at the higher intensity level, and thresholds were lower for patterns allowing greater opportunity for comparison within the patterns. When similar thresholds were obtained for patterns presented through speakers (Experiment II), thresholds were smaller, the influence of intensity was smaller, and the influence of (presentation) pattern type was less consistent. Significance of the findings is discussed.