Panoramic Uncertainty in Vertical Perception.

Janny C Stapel,W Pieter Medendorp

doi:10.3389/fnint.2021.738768

Janny C Stapel, W Pieter Medendorp

Open Access

https://doi.org/10.3389/fnint.2021.738768

Copy DOI

Abstract

Judgments of the orientation of a visual line with respect to earth vertical are affected by panoramic visual cues. This is illustrated by the rod-and-frame effect (RFE), the finding that the perceived orientation of a luminous rod is biased by the orientation of a surrounding squared frame. In this study, we tested how the uncertainty of frame orientation affects the RFE by asking upright or tilted participants to psychometrically judge the orientation of a briefly flashed rod contained within either a circular frame, a squared frame, or either of two intermediate frame forms, called squircles, presented in various orientations. Results showed a cyclical modulation of frame-induced bias across the range of the square and squircular frame orientations. The magnitude of this bias increased with increasing squaredness of the frame, as if the more unequivocal the orientation cues of the frame, the larger the reliance on them for rod orientation judgments. These findings are explained with a Bayesian optimal integration model in which participants flexibly weigh visual panoramic cues, depending on their orientation reliability, and non-visual cues in the perception of vertical.

Highlights

Many of our daily activities, such as walking, standing, or gaze control, rely on estimates of head and body orientation in space
The red curve is steeper than the blue and green curve, which indicates that the rod orientation estimate is more precise when the frame is upright rather than tilted
A third characteristic of the rod-and-frame effect (RFE) can be found when comparing the upper left and the upper right panel, namely, that the point-of-subjective equality (PSE) shifts with head tilt

Summary

INTRODUCTION

Many of our daily activities, such as walking, standing, or gaze control, rely on estimates of head and body orientation in space. The perceived orientation of an earth-vertical line is biased when surrounded by a tilted squared frame (Witkin and Asch, 1948; Alberts et al, 2016; Niehof et al, 2019), an effect known as the rod-and-frame effect (RFE; Witkin and Asch, 1948). Rules of Bayesian inference dictate that the most precise estimate (estimate with the lowest variance) of head orientation is achieved by integrating the sensory signals and prior expectations according to their reliability (Laurens and Droulez, 2007; MacNeilage et al, 2007; De Vrijer et al, 2008, 2009; Tarnutzer et al, 2009; Clemens et al, 2011; Alberts et al, 2016; Kheradmand and Winnick, 2017; De Winkel et al, 2018, 2021). The impact of frame orientation on the response variability was expected to be larger with increasing squaredness and more strongly so when the vestibular reliability was reduced

Participants

Experimental Setup

Experimental Procedure

RESULTS

DISCUSSION

ETHICS STATEMENT