The effects of random linear target direction in a computerized Dynamic Visual Acuity task

Abstract

Research on Dynamic Visual Acuity (DVA) to date has conventionally used visual targets originating from a single fixation point and moving in a single, predictable linear direction. These procedures (presumably dictated by apparatus constraints) ensured the observer knew when and from where the target would appear. A computerized test for DVA was developed and used to test DVA under viewing conditions not testable with conventional apparatuses. Two target direction conditions were compared over 3 durations (170, 370, 570 ms) and 5 velocities (0, 22, 45, 70, and 100 deg/s): fixed target direction (target originated from single fixation point, and moved horizontally from the observer’s left to the observer’s right, as has been the convention in DVA research over the past 57 years ) and random target direction (the target emanated randomly from one of six screen locations and move linearly across the screen to a point 180 deg opposite its origin). As hypothesized, the random direction condition, which may more closely represent DVA as applied in the real world, proved to be significantly more difficult relative to the fixed direction condition. Contrary to expectations of the current research as well as the general consensus in the DVA literature, data were also presented indicating that the generally accepted relationship between increased target velocity and increased DVA thresholds, may be in part the consequence of conventional apparatuses and procedures. The effect training was also investigated on under both fixed and random target direction conditions. No significant effect of training was demonstrated over four sessions, which may be a result inadequate sensitivity of the test. Strengths and weaknesses of a computer testing platform to test DVA are discussed.