Flexible Orientation Tuning of Visual Representations of Human Body Postures: Evidence From Long-Term Priming

Abstract

The proficiency of human observers to identify body postures is examined in three experiments. We use a posture decision task in which participants are primed with either anatomically possible or impossible postures (in the latter case the upper and lower body face in opposite directions). In a long-term priming paradigm (i.e., in an initial priming block of trials and a subsequent test phase several minutes later), we manipulate the relation between priming and test postures with respect to the identity of the person in the body postures (Experiment 1), the prototypicality of the depth orientations (Experiment 2), and the variability of the priming orientations (Experiment 3). Reaction time to the test postures is the main dependent variable. In Experiment 1 it is found that priming of postures does not depend on the exact visual appearance of the actor (either same priming and test female or male figure or different figures), supporting the hypothesis that posture priming primarily is determined by the spatial relations between the body parts and much less by characteristics of the person involved. Long-term priming in our paradigm apparently is based on the reactivation of high-level posture representations that make abstraction of the identity of the human figure. In Experiment 2 we observe that privileged or prototypical orientations (e.g., 3/4 views) do not affect long-term priming of body postures. In Experiment 3, we find that increasing or decreasing the variability between the priming and test figures influences reaction time performance. Collectively, these results provide a better understanding of the flexibility (e.g., invariant to identity) and limits (e.g., depending on depth orientation) of the processes supporting human posture recognition.

Representational momentum of biological motion in full-body, point-light and single-dot displays

“…Furthermore, recognition performances of briefly presented images of actions are higher when the images are in temporal continuity with previously presented priming movies of those actions 20 . This effect is robust to changes of the actor in the priming movies and the test images 21 and does not occur for biomechanically impossible movements 22 . Notably, RM has been also reported when human movements were presented by means of impoverished point-light stimuli (PLS), which are stimuli that consist of dots moving with the main joints of an actor performing different actions 23 .…”

Viewing angle matters in British Sign Language processing

“…Similarly, in a series of experiments using photographic stimuli, Daems and Verfaillie 37 found that seeing the same action or pose from a different viewing angle did not reliably facilitate later identification. Body posture representations appear to be angle-specific, such that priming effects dropped halfway when the angle difference between prime and target stimulus was 15°, and almost disappeared with a 30° rotation 37 , with the most finely tuned representations best supporting successful identification of similar postures from similar viewing angles 38 .…”