September 2019
Volume 19, Issue 10
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2019
Biases in the perception of the ambiguous motion quartet across spatial scale
Author Affiliations & Notes
  • Charlotte Boeykens
    Brain and Cognition, KU Leuven
  • Johan Wagemans
    Brain and Cognition, KU Leuven
  • Pieter Moors
    Brain and Cognition, KU Leuven
Journal of Vision September 2019, Vol.19, 152a. doi:
  • Views
  • Share
  • Tools
    • Alerts
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      Charlotte Boeykens, Johan Wagemans, Pieter Moors; Biases in the perception of the ambiguous motion quartet across spatial scale. Journal of Vision 2019;19(10):152a. doi:

      Download citation file:

      © ARVO (1962-2015); The Authors (2016-present)

  • Supplements

Perception of the ambiguous motion quartet is predominantly characterized by apparent motion in one of two directions. A vertical percept emerges when two dots presented in one frame are perceptually grouped over frames in a vertical direction (i.e. up-down) and vice versa for a horizontal percept (i.e. left-right). Previous studies have documented a vertical bias, indicating vertical apparent motion even when distances between dots across frames are equally large in both directions (Gengerelli, 1948). Wexler (2018) studied percepts of the motion quartet across different orientations and observed large inter-individual variability in biases varying within individuals over time. In this study, we asked whether vertical and horizontal percepts differed between and within individuals for presentations of stimuli across different spatial distances. More specifically, observers reported their percepts of motion quartets with an ISI of 320 ms displaying two dots with radii of 0.36 deg positioned in combinations of 25 horizontal and vertical distances ranging from 0.6 to 5.4 deg. A different group of observers did this task for combinations of 17 horizontal and vertical distances within the same range and repeated this task again after 30 minutes. In between, we measured individual points of subjective equality (PSE) in vertical distances for fixed horizontal distances (0.9, 1.5, 3.0 and 4.5 deg) by means of an adaptive procedure. Our results replicate the vertical bias in most observers, with considerable inter-individual variability where a minority showed veridical perception or even a horizontal bias. Biases did not vary substantially after 30 minutes. Interestingly, transitions between vertical and horizontal percepts seemed to scale with larger spatial distances, indicating that biases in perception are not invariant across spatial scale (i.e., the adaptive procedure showed that aspect ratios for PSEs became bigger and slopes of the psychometric functions became less steep for increasing spatial distances).


This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.