Abstract
Replacing the local dots of point-light walkers with complex images leads to significant detriments to performance in biological motion detection and discrimination tasks. This detriment has previously been shown to be larger when the local elements match the global shape in object category and facing direction. In contrast, studies using Navon stimuli have demonstrated that local interference on global processing primarily occurs when local elements are dissimilar to the global form. In 3 experiments, we investigated this contradiction by replacing the local dots of a point-light walker with human images or stick figures. Participants were significantly faster and more accurate at discriminating the facing and walking direction of a walker when the local images were facing in the same direction as the global walker than when they were facing in the opposite direction. These results provide support for the idea that organization of biological motion depends on allocation of limited processing resources to the global motion information when the local elements are complex. However, there is more disruption to global form processing when the local elements and global form conflict in task-related properties.
Highlights
Replacing the local dots of point-light walkers with complex images leads to significant detriments to performance in biological motion detection and discrimination tasks
The competing task of perceiving form information of the local figures can impair the integration of the individual elements into a coherent global form, especially when the local elements fall within a similar object category as the global shape
Accuracy Participants were significantly more accurate in identifying the walking direction of the global walker when the local images were facing in the same direction as the walker (M = 98.6 % ±0.66) than when they were facing in the opposite direction (M = 91.02 % ±3.68), t(32) = 5.0, p
Summary
Replacing the local dots of point-light walkers with complex images leads to significant detriments to performance in biological motion detection and discrimination tasks. They suggested that the discrimination of the facing direction of point-light walkers required only the first stage, whereas walking direction discrimination (forward/backward walking) required the sequential analysis performed in the second stage In support of this motion-from-form model, Wittinghofer, de Lussanet, and Lappe (2010) hypothesized that biological motion perception shares processing networks with other form-related tasks, such as object recognition. When the local human images were inverted, interference was reduced, providing further evidence that the local interference is due to form processing of body shape, as other visual features, as well as the motion of the images, are the same whether upright or inverted Extending their previous findings on object categories, Wittinghofer, de Lussanet, and Lappe (2012) proposed that the strength of interference depends on the similarity between the local objects and the global walker, and local figures facing in the same direction as the global walker should produce more interference than local figures facing in the opposite direction as the walker. As predicted, when local figures were facing in the same direction as the global walker, reaction times were slower than when the figures faced in the opposite direction; this effect was only true for facing-direction tasks. Wittinghofer et al (2012) concluded that these results support an orientation-specific interference effect, whereby objects that are most similar to the walker produce the largest impediment to performance due to shared processing mechanisms
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