Abstract
Our visual system rapidly extracts ensembles to help us understand our environment (Haberman & Whitney, 2012). However, it is not yet understood how multiple ensemble dimensions are used, or how attention can select one ensemble over another. As a first step, we investigated feature selection in attention for multi-dimensional ensembles. Specifically, we examined whether increasing featural differences, which aids perceptual grouping (Moore & Egeth, 1997), would boost selectivity for one ensemble over another. The perception of correlation in scatterplots appears to be an ensemble process (Rensink, 2017), and adding an irrelevant set of data points causes interference (Elliott & Rensink, VSS 2016; 2017). To investigate this more thoroughly, observers performed a correlation discrimination task for scatterplots containing both a "target" ensemble and an irrelevant "distractor" ensemble (Elliott & Rensink, VSS 2017) where target ensembles were distinguished by the color, shape, or color and shape combinations of their elements. Both tasks used ΔE from Szafir (2017) to create a precise experimental color space that takes into account stimulus area and mark type. Distractor colors varied in equal perceptual steps along three axes: luminance, chroma, and hue, which allowed us to investigate whether individual color dimensions influenced selection. Surprisingly, performance was equally good for targets defined by differences in single features and differences in two features. These results indicate that increasing feature differences between the two ensembles does not boost discrimination performance. Moreover, contrary to work by Nagy & Sanchez (1990) on hue differences in visual search, ensemble selection was equally effective along all three color dimensions in the task. And even very small differences along any color dimension were sufficient to facilitate ensemble selection.
Meeting abstract presented at VSS 2018