Previous studies in the wolf spider Lycosa tarantula (Linnaeus 1758) have shown that homing is carried out by path integration and that, in the absence of information relative to the sun's position or any pattern of polarized light, L. tarantula obtains information as to the angle it must turn to home through the anterior lateral eyes (ALEs). In the present study, spiders were trained to walk o...

Contrast thresholds for stereoscopic depth identification (crossed or uncrossed) were measured as a function of disparity using isoluminant (red-green) and isochromatic (yellow-black) 0.5 c/deg Gabor patches. For the purposes of comparison stimulus contrasts were scaled by their respective detection thresholds. The detection thresholds employed were computed from the monocular detection thresho...

We examined conditions under which two quite different types of random-dot cinematograms were perceptually matched. In one stimulus type, directions of motion were defined by a uniform distribution; in the other, directions were drawn from a discrete set of just a few, widely separated directions. Cinematograms whose range of uniformly distributed directions lay between 180 and 270 deg could be...

Primary barrier determinations for the shielding of medical radiation therapy facilities are generally made assuming normal beam incidence on the barrier, since this is geometrically the most unfavorable condition for that shielding barrier whenever the occupation line is allowed to run along the barrier. However, when the occupation line (for example, the wall of an adjacent building) runs per...

This study deals with the influence landmark information has on the foraging behaviour of the desert ant, Cataglyphis fortis, especially with the interaction of such landmark information with the ants' path integration system. We show in the first experiment that desert ants that are captured immediately after leaving their nest and then transferred to a remote test area search for the nest rat...

Disparity-evoked vergence is studied in stereograms showing one or two depth planes which are defined by isolated dots of varying density and contrast. Vergence position immediately after stimulus presentation was measured using dichoptic nonius lines. Since the stimulus was not visible after the onset of the vergence movement, the experiment accesses the initiation of vergence rather than its ...

We measured directional sensitivity to a foreground pattern while an orthogonally directed background pattern was present under transparent motion conditions. For both foreground and background pattern, the speed was varied between 0.5 and 28 deg sec-1. A multi-step paradigm was employed which results in a better estimation of the suppressive or facilitatory effects than previously applied sing...

Three experiments were conducted to investigate the effects of feature similarity and discrimination category in a flanker task. Gabor patches were used as target and distractor stimuli for each experiment. In the first experiment, the target turned to minus or plus 45 deg from the vertical, whereas the orientation of the distractors changed between minus and plus 45 deg by 15 deg. For the seco...

A curvilinear pattern among a series of visual items (e.g., dots) can be regarded as a kind of probabilistic inference, in which each consecutive angle, regarded independently, is more nearly collinear than would be expected by chance alone. This paper investigates judgments of curvilinearity as a function of the joint distribution of successive inter-dot angles. Subjects were asked to classify...

Several workers have concluded that Gabor alignment tasks are performed by using central tendencies of the micropatterns as a cue. One reason for this conclusion was that the 3-Gabor alignment task is performed equally well whether the orientations of the patches are collinear or orthogonal to the group orientation. We wished to find out if the orientation of the micropatterns has any effect on...