Brant Clark

Egocentric localization of the visual horizontal in normal and labyrinthine-defective observers as a function of head and body tilt

Perception of the visual horizontal by observers in five different combinations of head and body position was studied to determine the effect of 20-degree body tilts. Both normal and labyrinthine-defective observers made five settings to the visual horizontal for each condition using, a goggle device which presented a collimated line of light to the right eye while the other eye was covered. The results showed no significant constant errors in the settings by either group, and it is suggested that the absence of the E-phenomenon was due primarily to adequate contact cues and kinesthetic cues. The data also make it clear that vestibular information is not required for veridical perception of the visual horizontal under these experimental conditions.

Effects of Angular Acceleration on Man: Choice Reaction Time Using Visual and Rotary Motion Information

This experiment was concerned with the effects of rotary acceleration on choice reaction time (RTc) to the motion of a luminous line on a cathode-ray tube. Specifically, it compared the RTc to rotary acceleration alone, visual acceleration alone, and simultaneous, double stimulation by both rotary and visual acceleration. 13 airline pilots were rotated about an earth-vertical axis in a precision rotation device while they observed a vertical line. The stimuli were 7 rotary and visual accelerations which were matched for rise time. The pilot responded as quickly as possible by displacing a vertical controller to the right or left. The results showed a decreasing RTc with increasing acceleration for all conditions, while the RTc to rotary motion alone was substantially longer than for all other conditions. The RTc to the double stimulation was significantly longer than that for visual acceleration alone.

The power law for the perception of rotation by airline pilots

The purpose of this study was to determine the power laws for the perception of rotation about the three major body axes. Eighteen airline pilots made magnitude estimates of 5-sec pulses of nine angular accelerations having a range of acceleration x time of 10–150 deg/sec. The results showed that (1) the power law with an exponent of 1.4 describes the subjective motion of these pilots for all three major body axes, (2) the power law also describes the perception of motion for individual pilots with a substantial range of exponents, (3) there were significant correlations among the exponents for the three body axes, and (4) the data suggest that the power law over the wide range used may be more complex than implied by a formula with a single exponent.

Visual Space Perception as Influenced by Unusual Vestibular Stimulation

During flight in aircraft and spacecraft, pilots are regularly subjected to unusual force environments. These forces not only influence a variety of pressure-sensitive mechanisms but, in particular, they stimulate the vestibular mechanism of the inner ear. The latter source of information regarding spatial orientation may be in accord with information from direct visual stimulation or it may be in conflict with it. In the first case, veridical space perception may be expected, while in the second the perception is frequently nonveridical. This results in constant errors in judgment with respect to motion of visual objects and in the pilots estimates of the objects position. These errors, referred to by pilots as “vertigo,” are believed to be of importance in piloting aircraft and spacecraft where the pilots task involves actions based on visual space perception.

REACTION TIME TO ACCELERATING LINES AND DOTS ON A CATHODE-RAY TUBE

Two experiments recorded the simple RT of 13 and 10 airline pilots, respectively, to accelerating lines and dots on a cathode-ray tube. In Exp. 1, dotted lines of six lengths moved in-line or frontally, and downward or to the right. Exp. 2 compared seven different in-line-moving solid lines with dot pairs of corresponding separations, and with single dots. RT increased with the length of in-line-moving solid lines but not when dotted lines were used. RT decreased with frontal movement of dotted lines. RT to dot pairs was shorter than to solid lines or single dots. Results indicate the importance of three factors: amount of movement information, visual angle, and inhibition of the retinal area stimulated.

SOME RECENT STUDIES ON THE PERCEPTION OF ROTATION

Human rotation perception, discussing man-carrying rotation device, angular acceleration threshold, etc