Estimating heading during real and simulated eye movements

Abstract

The ability to judge heading during tracking eye movements has recently been examined by several investigators. To assess the use of retinal-image and extra-retinal information in this task, the previous work has compared heading judgments with executed as opposed to simulated eye movements. For eye movement velocities greater than 1 deg/sec, observers seem to require the eye-velocity information provided by extra-retinal signals that accompany tracking eye movements. When those signals are not provided, such as with simulated eye movements, observers perceive their self-motion as curvilinear translation rather than the linear translation plus eye rotation being presented. The interpretation of the previous results is complicated, however, by the fact that the simulated eye movement condition may have created a conflict between two possible estimates of the heading: one based on extra-retinal solutions and the other based on retina-image solutions. In four experiments, we minimized this potential conflict by having observers judge heading in the presence of rotations consisting of mixtures of executed and simulated eye movements. The results showed that the heading is estimated more accurately when rotational flow is created by executed eye movements alone. In addition, the magnitude of errors in heading estimates is essentially proportional to the amount of rotational flow created by a simulated eye rotation (independent of the total magnitude of the rotational flow). The fact that error magnitude is proportional to the amount of simulated rotation suggests that the visual system attributes rotational flow unaccompanied by an eye movement to a displacement of the direction of translation in the direction of the simulated eye rotation.

Controlling steering and judging heading: Retinal flow, visual direction, and extraretinal information.

“…The tasks used, however, required gaze sweep and fixation within a cloud, both of which provide more ambiguous flow fields than ground fixation. In addition, the display size used may have impeded accurate retinal analysis (Banks et al, 1996). Banks et al (1996) re-evaluated the two arguments.…”

“…In addition, the display size used may have impeded accurate retinal analysis (Banks et al, 1996). Banks et al (1996) re-evaluated the two arguments. Using the procedure of Warren and Hannon (1988), rotation was then added to the retinal image in one of two ways: either through real eye movements (RR) or by SR, and the proportion of each type of rotation was then varied.…”

“…2 Royden et al (1994) tested the role of this visual direction (VD) cue with 2 participants using a moveable clipping frame and found an advantage of VD for one participant (TRC) but not the other (MSB). This was present in Banks et al's (1996) Experiment 3but was removed in Experiment 4. Because the salience of the edge cue is increased when using a textured ground plane, we used a procedure that controlled for this VD cue.…”

“…A final issue with the experiments of Banks et al (1996) is that the results arose from testing three non-naïve participants (the experimenters) with a small range of headings (-4, 0, +4˚ ), and no statistical appraisal was made of the error pattern. We wished to reconfirm the role of ER signals with a larger group of naïve participants, with a wider range of headings, prior to translating the paradigm to a steering task.…”

“…For heading and steering tasks we used a different, but equivalent, method of reproducing the conditions of Banks et al (1996) using viewport motion (VPM) to manipulate the ER information. First, SR was added to the optic array using headings of up to ±12 o .…”