Abstract
Through ensemble encoding, the visual system compresses redundant statistical properties from multiple items into a single summary metric (e.g., average size). Numerous studies have shown that global summary information is extracted quickly, does not require access to single-item representations, and often interferes with reports of single items from the set. Yet a thorough understanding of ensemble processing would benefit from a more extensive investigation at the local level. Thus, the purpose of this study was to provide a more critical inspection of global-local processing in ensemble perception. Taking inspiration from Navon (Cognitive Psychology, 9(3), 353-383, 1977), we employed a novel paradigm that independently manipulates the degree of interference at the global (mean) or local (single item) level of the ensemble. Initial results were consistent with reciprocal interference between global and local ensemble processing. However, further testing revealed that local interference effects were better explained by interference from another summary statistic, the range of the set. Furthermore, participants were unable to disambiguate single items from the ensemble display from other items that were within the ensemble range but, critically, were not actually present in the ensemble. Thus, it appears that local item values are likely inferred based on their relationship to higher-order summary statistics such as the range and the mean. These results conflict with claims that local information is captured alongside global information in summary representations. In such studies, successful identification of set members was not compared with misidentification of items within the range, but which were nevertheless not presented within the set.
Highlights
Ensemble encoding is a well-established phenomenon where the visual system compresses redundant statistical properties from a given set of stimuli into a summary metric at the expense of detailed representations of single items. Ariely’s (2001) classic study demonstrated this, revealing that participants could accurately report the mean size of a set of circles, but were poor at identifying the size of any one individual circle from the set.Adrian Nestor and Jonathan S
Post hoc pairwise testing revealed accuracy was lower under high interference compared with low interference during reports of both average orientation and single orientation
A novel result of Experiment 1 is the existence of an implicit local interference effect when extracting a global summary statistic from an ensemble, evident by reduced accuracy when reporting average orientation under high interference where the distractor was a single item from the set, compared with low interference where the distractor value was outside the set
Summary
Ensemble encoding is a well-established phenomenon where the visual system compresses redundant statistical properties from a given set of stimuli into a summary metric at the expense of detailed representations of single items. Ariely’s (2001) classic study demonstrated this, revealing that participants could accurately report the mean size of a set of circles, but were poor at identifying the size of any one individual circle from the set.Adrian Nestor and Jonathan S. Marco Sama and Dilakshan Srikanthan are co first authors. Despite these findings, people typically have a subjective impression of seeing the entire stimulus set in good detail (Cohen, Dennett, & Kanwisher, 2016; Yamanashi Leib, Kosovicheva, & Whitney, 2016). The limited capacity of our visual working memory (VWM) places restrictions on the level of detail that we can extract from individual items within an ensemble. This disconnect between our subjective impression and veridical perceptual processing has been an enduring interest of cognitive scientists for decades
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