Abstract
Several steering models in the visual science literature attempt to capture the visual strategies in curve driving. Some of them are based on steering points on the future path (FP), others on tangent points (TP). It is, however, challenging to differentiate between the models’ predictions in real–world contexts. Analysis of optokinetic nystagmus (OKN) parameters is one useful measure, as the different strategies predict measurably different OKN patterns. Here, we directly test this prediction by asking drivers to either a) “drive as they normally would” or b) to “look at the TP”. The design of the experiment is similar to a previous study by Kandil et al., but uses more sophisticated methods of eye–movement analysis. We find that the eye-movement patterns in the “normal” condition are indeed markedly different from the “tp” condition, and consistent with drivers looking at waypoints on the future path. This is the case for both overall fixation distribution, as well as the more informative fixation–by–fixation analysis of OKN. We find that the horizontal gaze speed during OKN corresponds well to the quantitative prediction of the future path models. The results also definitively rule out the alternative explanation that the OKN is produced by an involuntary reflex even while the driver is “trying” to look at the TP. The results are discussed in terms of the sequential organization of curve driving.
Highlights
It was shown in [15] and [16] that the horizontal movement of the eye during the optokinetic nystagmus eye–movements (OKN) SP is in agreement with what one would predict if the driver is tracking waypoints on their future path (OKN slow phase horizontal angular velocity approximately 1⁄2 vehicle yaw rate)
By asking the drivers to keep their eyes on the TP the OKN pattern generated to “normal” driving, we were able to show that the robust OKN in the normal condition is not produced by an involuntary optokinetic reflex while “trying” to keep the gaze locked to the tangent point
We find the horizontal gaze speed during OKN SP quite nicely corresponds to this prediction
Summary
It was shown in [15] and [16] that the horizontal movement of the eye during the OKN SP is in agreement with what one would predict if the driver is tracking waypoints on their future path (OKN slow phase horizontal angular velocity approximately 1⁄2 vehicle yaw rate). Auxiliary assumptions about eye–movement reflexively following local optic flow at or around the tangent point (TP fixation + “noise” from unsuppressed OKR) could accommodate different eye-movement patterns into a tangent point model. This alternative explanation–while admittedly somewhat post–hoc–could not be ruled out in [16]. The main aim of the present study is to check the validity of the assumption that looking at the TP does lead to a measurably different gaze pattern from the OKN observed in natural driving. –by using the data from that experiment as a control group–we will be able show empirically that the gaze behavior observed in the “normal” condition (driving as normal) in the new experiment itself corresponds to natural driving (i.e. interleaving “normal” driving with “tp”–instruction to keep looking at the TP–does not in itself affect the “normal” pattern)
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