Daniel N. Robinson

Visual Disinhibition with Binocular and Interocular Presentations

Subjects were given combinations of two and three brief concentric flashes of equal luminance under backward masking conditions. Intervals between the first (TF) and second (CF) flashes were 10, 20, 50, 75, 100, and 200 msec. When third flashes (DF) were present, they were separated from CF by the same intervals. Two modes of presentation were employed: binocular presentations in which all flashes were presented to both eyes and interocular presentations in which TF and CF were presented to the left eye and DF to the right. With binocular view, the backward masking of CF by DF resulted in the disinhibition of TF, otherwise masked by CF under two-flash conditions. Disinhibition was not obtained under interocular presentations. A major conclusion is that recurrent influences within the human retina are not preserved more centrally (retrochiasmally) in the visual system.

Visual Discrimination of Temporal Order

Past research addressed to the minimum temporal separation necessary for the judgment of visual stimulus order has failed to control peripheral adaptation and masking effects. The present study employed pairs of brief stimuli with each member presented to a separate eye; that is, dichoptic presentations. Under these conditions, minimum separations for the correct discrimination of order were found to be far less than those obtained in experiments in which both stimuli were presented to the same eye or to both eyes.

EFFECTS OF SIGNAL-TO-NOISE RATIO AND TARGET ACCELERATION UPON THREE MEASURES OF RANGE TRACKING PERFORMANCE

Eight signal-to-noise ratios and four target accelerations were systematically varied in an attempt to determine functional relationships between these parameters and measures of time-on-target, frequency of target loss and the average duration of each loss on an A-scope compensatory tracking task. Nine Si were required to maintain a triangular pulse in the center of a stationary notch by manipulating a velocity controlled handwheel. The results indicated that visual noise had a pronounced effect upon time-on-target, but the effects of target acceleration were negligible. However, target acceleration had a pronounced effect upon frequency of losing target track and both parameters affected average duration of a loss. The results are discussed in terms of analyzing system performance.

Jefferson and Adams on the mind-body problem.

Amidst the voluminous correspondence between Thomas Jefferson and John Adams are several letters pertaining to the material basis of mental life. These reveal in a most suggestive way the substantial differences between them. Well informed on prevailing scientific and philosophical perspectives, Jefferson and Adams used the issue to express their positions on the nature and limits of knowledge, the relative authority of scientific methods and speculations, and the larger question of human perfectibility. At the same time, their exchanges illuminate the prevailing and divergent perspectives on human psychology adopted by major leaders of thought in the New World.

Prediction of Visual Tracking Proficiency on an A-Scope Presentation from the Measured Effects of Noise and Time

Visual noise and temporal requirements of a compensatory tracking task were varied in order to determine time-on-target proficiency. Nine Ss were each given 32 trials in counterbalanced order, with problems varying as to visual noise and target acceleration. The display consisted of an A-scope with Ss task being to maintain a triangular pulse in the center of a stationary notch by manipulating a velocity controlled handwheel. The results were plotted as a family of curves describing probable success as a function of visual noise and task time allowed. Probability of success became greater as the time requirements became less severe, and when time requirements became more severe, not only did probability of success diminish, but the differential effects of noise became more pronounced. The authors suggested this approach as a method of predicting subsequent tracking behavior.

STEREOSCOPIC FACILITATION OF SIGNAL DETECTION.

A small depth enhancement in tracking high acceleration targets (0.6 g) at a signal-to-noise ratio of 0.0 db was observed for increased intensity disparity between the eyes. Parametric study is needed.