Hypothetical neural codes underlying the sensation of tactile roughness were investigated in a combined psychophysical and neurophysiological study. The stimulus set consisted of plastic surfaces embossed with dot arrays of varying dot diameter and center-to-center spacing. Human subjects explored each surface with the pad of the index finger and reported their subjective sense of roughness mag...

The purpose of the present study was to measure contrast sensitivity to equiluminant gratings using steady-state visual evoked cortical potential (ssVECP) and psychophysics. Six healthy volunteers were evaluated with ssVECPs and psychophysics. The visual stimuli were red-green or blue-yellow horizontal sinusoidal gratings, 5° × 5°, 34.3 cd/m2 mean luminance, presented at 6 Hz. Eight spatial fre...

Vision measurement is the basis for the study and standardization of visual sciences. Measurement of visual acuity has great value for research and for clinical practice. This paper (1) reviews the fundamental concepts to understand visual sense and the measuring units; (2) presents the fundamental limits to visual performance and the principles of aberration measurement of the eye; and (3) dis...

Attention is the mechanism that allows us to selectively process the vast amount of information that we receive and to guide our behaviour. Visual spatial attention can be deployed overtly, accompanied by eye movements to the relevant location, or covertly, without eye movements (Helmholtz 1910/1925, Posner 1980). There are two types of covert attention: sustained attention refers to the volunt...

The experimental evidence regarding Gibson's psychophysical hypothesis is examined. The presentation is divided into 2 sections dealing with static and transforming stimulation, respectively. Under the former heading the stimulation for surface, slant, and depth is considered. Under the latter heading the investigations of motion perspective, continuous perspective transformations, and size-tra...

A central theoretical assumption in classical psychophysics is that people judge the intensities of stimulus elements; for example, observers directly report the loudness of a tone or the intensity of a shock. A methodological assumption in classical psychophysics is that averaged data demonstrate this theoretical view. It is shown in this article that both assumptions are wrong and that the ps...