Separate timescales for spatial and anatomical information processing during action observation
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Introduction
Observing actions primes us to perform similar movements. Prior work indicates this effect is influenced by factors such as spatial congruence, perspective, and presenting biological/non-biological stimuli. We hypothesized that the influence of these factors would vary depending on the amount of time that participants had to process visual stimuli.
Method
Experiment 1 was a reaction time task (n=29) with stimuli varying in spatial congruence (congruent, incongruent, neutral), perspective (first- or third-person) and stimulus type (biological or non-biological). Experiment 2 (n=50) used the same stimuli in a “Forced Response” paradigm, which controlled the time participants had to prepare a response. This allowed us to assess responses as a function of preparation time.
Results
Experiment 1 showed effects of spatial congruence, with longer reaction times and more errors for spatially incongruent stimuli. This effect was greater for biological stimuli. Experiment 2 showed that spatial information was processed faster than anatomical information, inducing incorrect responses at short preparation times for spatially incongruent biological stimuli. There was little-to-no corresponding effect for non-biological stimuli. Both experiments also showed weak-to-no effects of perspective, which appear to have been driven by spatial congruence.
Discussion
Our results indicate that spatial information is processed faster than anatomical information during action observation. These data are consistent with the dual visual streams hypothesis, whereby spatial information would be processed rapidly via the dorsal stream, while anatomical processing would occur later via the ventral stream. These data also indicate differences in processing between biological and non-biological stimuli.
Public significance statements
This study provides novel insight into the time-course of information processing, showing that spatial information is processed faster than anatomical information during action observation. The results also challenge the established view that visual perspective is critical to action observation effects, demonstrating that this may instead result from lower-level effects of spatial congruence.
