Abstract
We live in a cluttered, dynamic visual environment that poses a challenge for the visual system: for objects, including those that move about, to be perceived, information specifying those objects must be integrated over space and over time. Does a single, omnibus mechanism perform this grouping operation, or does grouping depend on separate processes specialized for different feature aspects of the object? To address this question, we tested a large group of healthy young adults on their abilities to perceive static fragmented figures embedded in noise and to perceive dynamic point-light biological motion figures embedded in dynamic noise. There were indeed substantial individual differences in performance on both tasks, but none of the statistical tests we applied to this data set uncovered a significant correlation between those performance measures. These results suggest that the two tasks, despite their superficial similarity, require different segmentation and grouping processes that are largely unrelated to one another. Whether those processes are embodied in distinct neural mechanisms remains an open question.
Highlights
In our everyday lives, objects of interest to us are sometimes not so easy to see because of the cluttered visual context in which they appear
Because the reliability of a measure constrains the magnitude of the correlation that it can have with another measure (Nunnally and Bernstein, 1991), we addressed whether the nonsignificant correlations that we observed between biological motion discrimination (BM) and fragmented figures (FFs) were due to measurement error
Our focus was on the potential correlation in performance between BM and FF, with the gabor patch detection (GD) task included to evaluate a possible contribution from non-sensory factors that could have produced a significant correlation between the two tasks of interest
Summary
Objects of interest to us are sometimes not so easy to see because of the cluttered visual context in which they appear. Our understanding of perceptual organization has benefitted greatly from the development of psychophysical strategies for isolating the contributions of specific operations putatively involved in object perception One such strategy is exemplified by the fragmented figures technique popularized by Snodgrass et al (1987). Fragmented figures allow one to assess quantitatively the effect of figure degradation on picture identification and to exploit figure degradation to study processes such as perceptual learning (Doniger et al, 2001a), visual priming (Snodgrass and Feenan, 1990), and implicit and explicit memory (Russo et al, 1995) Another popular stimulus strategy for studying perceptual organization involves the use of point-light (PL) animations to portray biological motion. Biological motion portrayed by PL animation has been widely used in recent years to study dynamic perceptual organization in children (Pavlova et al, 2001; Friere et al, 2006), young adults (Hiris, 2007) and the elderly (Norman et al, 2004; Billino et al, 2008; Pilz et al, 2010), as well as in clinical populations including people with autism (Moore et al, 1997; Blake et al, 2003; Kaiser and Shiffrar, 2009; McKay et al, 2012; Nackaerts et al, 2012), prosopagnosia (Lange et al, 2009), schizophrenia (Kim et al, 2005, 2011; Spencer et al, 2013), and brain damage (Cowey and Vaina, 2000; Pavlova et al, 2003)
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