Abstract
Westheimer and McKee (1978, Journal of the Optical Society of America, 68(4), 450-455) reported that stereoacuity is unaffected by the speed of moving vertical line targets by up to 2 deg/s. Subsequent studies found that thresholds rise exponentially at higher velocities (Ramamurthy, Patel & Bedell, 2005, Vision Research, 45(6), 789-799). This decrease in sensitivity has been attributed to retinal motion smearing; however, these experiments have not taken into account the additional effects of display persistence. Here we reassess the effects of lateral velocity on stereoacuity in the absence of display persistence, using physically moving stimuli. Luminous vertical line targets were mounted on computer-controlled motion stages. This purpose-built system permitted precise control of target position and movement, in three dimensions. In a 1IFC paradigm with 120ms viewing duration, observers fixated a stationary point and discriminated the relative depth of the two moving lines. The velocity of the line pair ranged from 0 (stationary) to 16 deg/s; each speed was tested in a separate block of trials. Our results confirm the resilience of stereoacuity to lateral retinal motion at velocities less than 2 deg/s. At higher speeds, for all observers thresholds increased marginally with speed. The rate of increase was 0.6 arc seconds per deg/s which was approximately 10 times smaller than reported by Ramamurthy et al. (2005). It is clear that stereoacuity is more robust to lateral motion than previously believed; we argue that the threshold elevation reported previously is largely due to display persistence.
Meeting abstract presented at VSS 2015