Time-to-passage estimation on periphery : better for biological motion?

Abstract

In previous studies, complex motion stimuli were judged as passing sooner than rigid stimuli but reflected more uncertainty in the judgments as revealed by precision loss and longer reaction times. It is known that biological motion can be perceived in the periphery . In the everyday life people are required to interact with or to estimate motion variables of other agents located on the periphery , at different locations of the visual field. In this study , stimuli were presented in different peripheral location (16°, 32° and 48°). In a time-­to-­passage (TTP) task rigid (RM), biological (BM) and scrambled (SM) motion conditions were compared. Seven simulated velocities were combined with seven starting distances, resulting in 49 levels of TTP: 24 conditions that arrived before 1s and 24 that arriving after 1s. Subjects had to decide whether the point-‐‑light walker (PLW) passed the eye plane before or after a reference time (1s) signaled by a tone. Subjects could judge time to passage of PLW peripherally to an eccentricity of at least 48o. Judgments for complex motion patterns (BM and SM) showed an anticipation of the passage combined with a loss of precision when compared with RM, at eccentricity 16o. The effect of eccentricity on precision was revealed by the increase of SD along eccentricities for SM. The TTP judgment seemed to become less precise as the stimuli were displaced farther along the peripheral field. For BM, an improvement on precision was verified at eccentricity 32o, and a subsequent deterioration just at eccentricity 48o. The anticipation of the passage for BM was no longer found on periphery , while the differences on the precision between BM and RM vanished.