Test target

Abstract: In visual search tasks, targets are detected more rapidly when they appear in locations that commonly contain a target than when they appear in locations that rarely contain a target. Five experiments were conducted to investigate two specific properties of this location probability effect: its dependence on spatial location versus relative position and its dependence on or independence of target identity. In Experiment 1 spatial location of a stimulus row was varied to determine whether high location probability facilitates target detection in a particular location in visual space or a particular relative position within the row. Both were facilitated to approximately the same extent. In Experiment 2 an inducing target occurred with high probability in one of four display locations, and a test target occurred with equal probability in all four locations. Both targets were found more quickly in the high-probability location than in the other locations, but the advantage associated with targets in the high-probability location was larger for the inducing target than for the test target. In Experiments 3-5 the correspondence between the components observed in Experiments 1 and 2 was examined. The overall pattern of results was compatible with a model in which the location probability effect is produced partly by an attentional spotlight, which facilitates processing of any stimulus appearing in a particular location in visual space, and partly by a network of position-specific letter detectors, which facilitates detection of a particular letter in a particular relative position within a display. Models with flexible scanning strategies were also considered.

Abstract: An attention performance test uses a visual display, a test subject input device, a memory and a programmed processor coupled to each of the above to administer a test to a test subject A test target, which for example can be a word colored in a first color but meaning another color, is attempted to be matched by the test subject to one of a series of sequentially presented visual response targets In one embodiment, a nonvisual test stimulus is also provided to the test subject, the test subject having previously been instructed to respond to the nonvisual test stimulus (such as a beep) in a particular way The test also measures the response latency of the test subject, ie, whether the test subject has assumed a correct position for entering a response The responses from the test subject are recorded and may be compared with data derived from a test subject database in assessing whether an attention deficit disorder exists

Abstract: The perceived velocity of visually tracked moving objects may depend on interactions between reflexive and voluntary oculomotor mechanisms. To investigate this hypothesis, subjects were required to compare sequentially the velocity of a standard target with that of a test target moving at one of five velocities. The standard target was viewed against a plain field (no optokinetic stimulation), and the test target was viewed against (1) a plain field, (2) a stationary grating, (3) a grating drifting in the direction of target motion, or (4) a grating drifting against target motion. In one condition, subjects tracked the target; in the other, a stationary point was fixated. The tracking group overestimated velocity when backgrounds drifted against target motion, but underestimated velocity when gratings drifted with target motion. Subjects not required to track experienced no such misestimations. The results are discussed in relation to the interactive mechanisms of the two eye-movement systems.

Abstract: Visual excitability changes were obtained from two trained observers by measuring threshold with a brief test flash of light at varying temporal intervals from the onset of a longer, supraliminal conditioning flash. The test target was either a 1°209 or a 5°209 solid disc, and was exposed to the right eye at 6°409 along the horizontal meridian in the temporal half field. The conditioning target was a 6°409 disc containing central masks of various angular subtenses, and was so placed in the left eye that the resulting annuli surrounded the test target in the binocularly fused field of view. For all conditions, threshold rose when test preceded conditioning flash in time, reaching a maximum at about o-msec interval between onsets. As the test flash was progressively delayed in time, thresholds fell to an asymptote, returning to resting level after termination of the conditioning flash. The smaller the mask diameter in the center of the conditioning target, i.e., the tighter the fit around the binocularly fused test target, the greater the maximum rise in threshold in the other eye. With small test targets, greater threshold changes were produced by conditioning targets with small masks than by those without a mask (solid targets). Observations on a third observer indicate that similar findings obtain when conditioning stimuli are equated for total luminous flux. These data indicate that retrochiasmal interaction is greater at target borders, and are compatible with recent unit studies on the cortical receptor field.