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

Karl Verfaillie,Anja Daems

doi:10.3389/fpsyg.2020.00393

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.

Highlights

Human observers exhibit an impressive level of proficiency in identifying the body postures of conspecifics
The remaining reaction time (RT) were entered in a subject repeated-measures analysis of variance (ANOVA) with priming condition as a within-subject variable and participant group as a between-subjects variable, and in a stimulus ANOVA with priming condition as within-stimulus variable and stimulus group as between-stimuli variable. (Especially in psycholinguistic research, and in perception research, it is informative to perform both subject and stimulus analyses and present them together, Kirk, 1968; Pittenger, 2003, as we did in previous analyses of experiments with the same paradigm; Daems and Verfaillie, 1999; Verfaillie and Daems, 2002)
This priming effect was not significantly larger when the human model in the priming posture was identical to the model in the test phase than when priming and test postures were personated by distinctly different human models

Summary

Introduction

Human observers exhibit an impressive level of proficiency in identifying the body postures of conspecifics (e.g., Daems and Verfaillie, 1999; Rumiati, 2000; Willems et al, 2014 (much like the recognition of faces; e.g., Galton, 1883; Maurer et al, 2002; Van Belle et al, 2010a,b; Verfaillie et al, 2014; Vrancken et al, 2019, the issue whether face and body recognition are “special” is under debate, e.g., Gauthier et al, 1999; Tai et al, 2004; Reed et al, 2012). In order to investigate the nature of the representations underlying visual perception of human body postures, Daems and Verfaillie (1999), Experiments 3 and 4) developed a posture decision task in combination with a long-term priming procedure. In an initial priming block, a static picture of a particular human body posture was shown. Daems and Verfaillie (1999) observed a long-term priming effect: In the testing phase, participants were on average about 35 ms faster to decide that a posture was anatomically possible when they had seen the posture before in the priming block than when they encountered the posture for the first time in the testing block Some of the test postures were already presented in the priming block, whereas other postures were new. Daems and Verfaillie (1999) observed a long-term priming effect: In the testing phase, participants were on average about 35 ms faster to decide that a posture was anatomically possible when they had seen the posture before in the priming block than when they encountered the posture for the first time in the testing block

Methods

Results

Conclusion