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. 2013 Jun 26;4(5):333-46.
doi: 10.1068/i0590. eCollection 2013.

Displaying optic flow to simulate locomotion: Comparing heading and steering

Georgios K Kountouriotis  1 , Richard M Wilkie  2
Affiliations

Displaying optic flow to simulate locomotion: Comparing heading and steering

Georgios K Kountouriotis et al. Iperception. .

Abstract

Optic flow can be used by humans to determine their direction of heading as well as controlling steering. Dot-flow displays have been widely used to investigate these abilities but it is unclear whether photorealistic textures would provide better information for controlling high-speed steering. Here, we examine the accuracy of heading judgements from dot-flow displays of different densities and luminance and then compare to a scene containing a textured ground. We then examine steering behaviour using these same displays to determine whether accurate heading conditions necessarily equate to successful steering. Our findings suggest that the bright dense dot-flow displays led to equivalent performance as the ground texture when judging heading, and this was also true when steering. The intermediate dot-flow conditions (with fewer and faded dots) revealed that some conditions that led to accurate heading judgements were insufficient for accurate steering. It seems, therefore, that heading perception should not be considered synonymous with successful steering control, and displays that support one ability will not necessarily support the other.

Keywords: dot flow; heading; locomotion; optic flow; steering; texture.

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Figures

Figure 1.
Figure 1.
Example display for the denser dot-flow condition (33.75 dots/m2) in the upper panel and the photorealistic “texture” condition in the lower panel. The scene was clipped at 50 m in both experiments. Participants viewed the scene binocularly without any head-movement restrictions.
Figure 2.
Figure 2.
Top-down view of steering trajectories of all conditions for one participant (solid black lines). These trajectories were extrapolated (grey lines) using curve-fitting algorithms on the last 0.66 s of each trial in order to calculate steering error relative to the steering target (black circle).
Figure 3.
Figure 3.
Comparing RMS errors in the Heading (a–c) and Steering (d–f) experiments. (a) Heading errors for the different levels of flow visibility (open symbols = “faded”; filled symbols = “visible”) and different numbers of dots on the ground. For a comparison, the error for the textured ground condition is shown by the dotted line ± standard error of the mean (SEM) (grey rectangle); (b) heading errors for the different heading angles (triangles = 18°, squares = 14°, and diamond = 10°) and different numbers of dots on the ground; (c) heading errors for the different levels of flow visibility (open symbols = “faded”; filled symbols = “visible”) across different heading angles. Panels (d–f) match (a–c) but depict steering error. The only difference in conditions to note is that in (e) the initial heading angle of 10° was replaced by an angle of 22° (filled circles) and the vertical scale has been increased to 10°. In all cases, bars represent the SEM.
Figure 4.
Figure 4.
(a) The interaction between number of dots and dot visibility for signed heading error. (b) The interaction between number of dots and heading angle for signed heading error.
Figure 5.
Figure 5.
(a) The interaction between number of dots and visibility condition and (b) the interaction between initial heading angle and visibility condition for signed steering error.
Figure 6.
Figure 6.
The main effect of the flow condition for the Steering and Heading experiments using only the two common angle conditions between the two experiments.
See this image and copyright information in PMC

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