Of a perceptual group or “blob” regardless of ISI. In a secondĮxperiment, it was found that figurai nonidentity between elements of successive frames always resulted in apparent movement The entire groups of letters and thereby ignored figurai relationships in their percepts of apparent movement. However, when the frames were alternated with an 80-msec ISI, observers reported apparent movement of frames were alternated with a 20-msec ISI, observers maintained local figurai identity in their percepts In such a way that the letters I, T, and E appeared in corresponding locations while the M was in disparate locations betweenįrames. Stimulus frames containing the words MITE and ITEM were constructed Of motion perceived in bistable apparentovement displays. Two experiments investigated the importance of figurai relationships among stimulus elements in the determination of the kind When local first-order motion signals are weakened by appropriate temporal and spatial conditions or by incoherent motion directions, higher-order SM dominates and it captures the motion of dots. The results show that, when the distance of dot jump is large or when the directions of dots' motion are incoherent, higher-order SM arises more frequently. Experiment 2 tested which factor caused the domination of higher-order SM under uncorrelated conditions in Experiment 1, the larger distance of dot jump or the varied directions of the dots' motion. Subjects reported that, when higher-order SM was seen, dots were attached to the surfaces of the moving cyclopean figure (motion capture). When they were uncorrelated, higher-order SM dominated even under zero ISI conditions. ![]() The results show that, when the spatial arrangements of two-frame random dots were correlated, higher-order SM dominated for long ISI conditions (ISI > 73 msec). Experiment 1 explored the conditions under which higher-order SM frequently arose, as opposed to local luminance-based in-depth motion (first-order SM). or lateral motion of gratings (higher-order stereoscopic motion, higher-order SM). Alternation of two-frame stereograms whose phases differed by 90 deg caused two kinds of percepts, planes' motion in depth (first-order stereoscopic motion, first-order SM). Vertical stripes of cyclopean square gratings were simulated by random-dot stereograms. ![]() In addition to fundamental findings, these results may have conservation value and assist in improving translocation strategies for endangered tortoise populations.Īn interaction in apparent motion between perceived three-dimensional forms defined by stereopsis and local luminous elements is reported. These results suggest that challenging habitats increase boldness. Immature tortoises were less willing to jump compared to larger and more experienced adults. Individuals from the flat habitat were reluctant to jump, whereas most tortoises from the rugged habitat jumped. We compared the behaviour of the tortoises (taking a risk to ‘jump’ or waiting) from two populations living in contrasted habitats: flat versus rugged (crisscrossed by cliffs and rocky steps). In their natural habitat, individuals were positioned in a challenging situation: they were placed on a bench approximately 50 cm high, and were observed over a 10-min period. In this context, we examined an important behavioural trait: how tortoises (Testudo hermanni) deal with step-like obstacles. Although crucial, studies exploring how tortoises move in complex and irregular environments are scarce. The first two hypotheses were confirmed and qualitative data were obtained supporting the third.ĭespite exhibiting low velocity and limited agility, many tortoises undertake large scale movements and must overcome various obstacles, notably in populations living in hilly or rocky habitats. (3) When moving out of synchrony with a given plane, a stimulus object will be seen as moving laterally (as well as shifting in depth) until it achieves synchrony with the other plane, at which time it will be perceived as static. ![]() (2) Viewed by a moving subject, a middle-ground object that is being shifted from synchrony with one plane to synchrony with the other plane will be judged as moving away from the original plane toward the other plane. Three hypotheses were advanced: (1) Viewed by a moving subject, a middle-ground object moving in synchrony with static objects in either a foreground or background plane will be judged as static and at the depth of the synchronous plane. Employing a model visual field with splotched backdrop, two planes of static gray balls and an intermediate moving red stimulus ball were presented while subjects were also under various conditions of lateral movement. ![]() This experiment was designed to study the influence of motion parallax on depth and movement perception.
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