Reaction time and visual brightness: within-subject correlations.

An experiment was conducted to compare visual reaction time and visual brightness within the same subjects. Simple reaction times and magnitude estimates of brightness were obtained in response to 1000-msec. flashes of 60.7, 67.5, 76.4, 85.1, and 93.4 dB re 10(-10)L white light. The relationship between reaction time and stimulus intensity was best described by a negative logarithmic function, while the relationship between magnitude estimates of brightness and stimulus intensity was best described by a power function. Linear correlations between reaction times and magnitude estimates indicated that visual reaction time and brightness are not proportional within all subjects. Previous reports of proportionality between these two measures were discussed as possibly being the result of inappropriate cross-experiment comparisons.     

Relations among comfort of fabrics, ratings of comfort, and visual vigilance

Little is known about the relationship between perceptions of comfort and cognitive performance. In the present study, 40 subjects (20 men and 20 women) participated in a computerized cognitive task of visual vigilance. The computer task was completed under three conditions of clothing and tactile comfort: one condition was that of extreme discomfort, effected by the wearing of wool clothing material on the arms and neck in addition to each subject's normal clothing, including a short sleeve shirt; a second condition was that of minimal discomfort, effected by the wearing of cotton clothing material on the arms and neck, in addition to each subject's normal clothing, including a short sleeve shirt; and a third condition was a control, wherein no experimental material was added to each subject's normal clothing, including a short sleeve shirt. Comfort was assessed prior to, during, and after testing. Reaction time and accuracy of 400 trials of a visual vigilance task were assessed under each of these three conditions. Analysis indicated a significant difference in perceived comfort between the wool and each of the other conditions. In addition, both reaction time and accuracy declined in the wool condition. This study is among the first to identify a direct significant relationship between perceptions of clothing comfort and cognitive performance.     

Comparison of taste qualities elicited by tactile,electrical, and chemical stimulation of single human taste papillae

Taste quality responses elicited by chemical, electrical, and tactile stimulation of 40 single fungiform papillae in four subjects were examined. A comparison of responses revealed differences in taste quality mediation for the three different classes of stimuli. Chemical stimulation elicited multiple taste qualities from a greater proportion of papillae than did either electrical or tactile stimulation. In addition, the chemical data revealed the presence of consistent bitter-sour and sour-salty confusions. Both tactile and electrical stimulation elicited relatively few bitter and sweet responses, as compared with either sour or salty responses. However, correct quality identification in these papillae for bitter and sweet compounds was no different from that for sour or salty compounds. In addition, electrical stimulation elicited a greater proportion of salty responses than did tactile stimulation. Comparison of the taste quality elicited by either tactile or electrical stimulation of a papilla with the taste quality exhibiting the greatest relative chemical sensitivity in the papilla also revealed independence of responding, and it was observed that both electrical and tactile stimulation elicited consistent taste quality responses from papillae in which these taste qualities could not be elicited by any concentration of any chemical test compound. The observed differences in quality judgments are discussed as possibly being the result of cross-modal gustatory associations resulting from nongustatory components of inadequate stimulation.     

Psychophysical exponents for single papillae: A comparison with whole-mouth exponents

Taste intensity judgments in response to chemical stimulation of single human fungiform papillae were obtained by the method of magnitude estimation. Intensity scales constructed from these data were compared to those obtained from the same subjects in response to stimulation of the whole mouth. Single papilla functions conformed well to the power law governing the growth of sensation magnitude, although a minority of single papilla functions exhibited peaking of response magnitude at intermediate concentrations, followed by a decline in response magnitude at higher concentrations. Single papilla exponents were found to be lower than whole mouth exponents and were positively correlated with detection and/or recognition thresholds of the papillae for most compounds. Exponents of summated single papilla functions were greater than median single papilla exponents, but their relative magnitude vs. whole mouth exponents varied by test compound. The data were discussed in relationship to previous findings concerning flow rate effects, threshold-exponent relationships across the tongue surface, and level-dependent spatial summation.