Abstract
Most attentive motion tracking studies have been restricted to central vision. Peripheral vision can support global and biological motion perception, although speed thresholds and noise tolerance are poorer than in central vision. We investigated peripheral attentive motion tracking using a multiple object tracking (MOT) task (n=15, 27±3 years of age). The potentially confounding effect of crowding was assessed by 1) manipulating the spacing between MOT task elements, and 2) conducting a numerosity judgement control experiment. Speed thresholds for a multiple object tracking (MOT) task involving 4 circular targets (1° diameter) and 4 identical distractors were measured using a 2-up 1-down staircase. Thresholds (based on partial report) were measured across 4 eccentricities (0°, ±5°, ±10°, and ±15°) with minimum element spacing set to 0.15°, 0.6° and 1.5°. The numerosity judgement task involved presentation of static frames from the MOT task within a temporal 2-alternate forced choice paradigm. Participants (n=12) judged which frame contained the most elements. MOT speed thresholds fell with eccentricity for every stimulus spacing. There was an approximately 5-fold reduction in threshold from central vision to 15° of eccentricity. There were no hemifield effects. Analyses of the speed thresholds revealed an interaction (F = 12.25, p< 0.001) between eccentricity and element spacing whereby an advantage of larger stimulus spacing in central vision was absent in the periphery. The opposite effect (F = 49.05, p< 0.001) was observed for the numerosity control task, whereby an advantage of larger stimulus spacing was more pronounced in the periphery than in central vision. This suggests that the effect of eccentricity on MOT speed thresholds was not solely due to peripheral crowding. Our results indicate that although attentive motion tracking is possible in the periphery, speed thresholds are dramatically reduced. This may limit the use of peripheral vision for attentive tracking in real-world situations.
Meeting abstract presented at VSS 2017