Egocentric Direction and Position Perceptions are Dissociable Based on Only Static Lane Edge Information

The Role of Quiet Eye Timing and Location in the Basketball Three-Point Shot: A New Research Paradigm

We investigated three areas of uncertainty about the role of vision in basketball shooting, the timing of fixations (early, late), the location of fixations (hoop centre, non-centre) and the effect of the defender on performance. We also sought to overcome a limitation of past quiet eye studies that reported only one quiet eye (QE) period prior to a phase of the action. Elite basketball players received the pass and took three-point shots in undefended and defended conditions. Five sequential QE periods were analyzed that were initiated prior to each phase of the shooting action: QE catch, QE arm preparation, QE arm flexion, QE arm extension, and QE ball release. We used a novel design in which the number of hits and misses were held constant by condition, thus leaving the timing and location of QE fixations free to vary across the phases during an equal number of successful and unsuccessful trials. The number of QE fixations accounted for 87% of total fixations. The greatest percent occurred during QE catch (43.6%), followed by QE arm flexion (34.1%), QE arm extension (17.5%) and QE ball release (4.8%). No fixations were found prior to QE arm preparation, due to a saccade made immediately to the target after QE catch. Fixation frequency averaged 2.20 per trial, and 1.25 during the final shooting action, meaning that most participants had time for only one fixation as the shot was taken. Accuracy was enhanced when: (1) an early QE offset occurred prior to the catch, (2) an early saccade was made to the target, (3) a longer QE duration occurred during arm flexion, and (4) QE arm flexion was located on the centre of the hoop, rather than on non-centre locations. Overall, the results provide evidence that vision of the hoop was severely limited during the last phase of the shooting action (QE ball release). The significance of the results is explored in the discussion, along with a QE training program designed to improve three-point shooting. Overall, the results greatly expand the role of the QE in explaining optimal motor performance.

High-normal blood glucose levels may be associated with decreased spatial perception in young healthy adults

The negative effects of high normal glucose on cognitive function were previously reported in euglycemic individuals of middle age and the elderly population. This study aimed at examining the effect of baseline blood glucose levels on spatial ability, specifically verticality perception on the computerized rod and frame test (CRFT) in young healthy adults. 63 healthy male medical students (age range from 18-23 years), of whom 30 were non-fasting outside the month of Ramadan and 33 fasting during Ramadan of the year 2016, were recruited in order to create varying degrees of glycemia during which verticality perception was carried out. Baseline blood glucose reading was obtained prior to commencing the CRFT test. Blood glucose levels at the time of testing decreased as the duration between the last meal and testing increased. A blood glucose range of 62-117 mg/dl was achieved among participants for this study. Linear regression analysis showed that blood glucose level at testing correlated positively with all alignment spatial error parameters, indicating a probable reduction of spatial perception ability with higher blood glucose levels. These results are consistent with other cognitive studies in older healthy humans and emphasize the critical impact of early glucose dys-homeostasis on cognitive function. They also indicate that elevated blood glucose may affect cognitive functioning outside of the usual complications of diabetes.

Peripersonal versus extrapersonal visual scene information for egocentric direction and position perception

When perceiving the visual environment, people simultaneously perceive their own direction and position in the environment (i.e., egocentric spatial perception). This study investigated what visual information in a scene is necessary for egocentric spatial perceptions. In two perception tasks (the egocentric direction and position perception tasks), observers viewed two static road images presented sequentially. In Experiment 1, the critical manipulation involved an occluded region in the road image, an extrapersonal region (far-occlusion) and a peripersonal region (near-occlusion). Egocentric direction perception was worse in the far-occlusion condition than in the no-occlusion condition, and egocentric position perceptions were worse in the far- and near-occlusion conditions than in the no-occlusion condition. In Experiment 2, we conducted the same tasks manipulating the observers' gaze location in a scene-an extrapersonal region (far-gaze), a peripersonal region (near-gaze) and the intermediate region between the former two (middle-gaze). Egocentric direction perception performance was the best in the far-gaze condition, and egocentric position perception performances were not different among gaze location conditions. These results suggest that egocentric direction perception is based on fine visual information about the extrapersonal region in a road landscape, and egocentric position perception is based on information about the entire visual scene.