Now you see it, now you don't: The context dependent nature of category-effects in visual object recognition

Abstract

In two experiments, we test predictions regarding processing advantages/disadvantages for natural objects and artefacts in visual object recognition. Varying three important parameters*degree of perceptual differentiation, stimulus format, and stimulus exposure duration*we show how different category-effects can be provoked in normal subjects on the same task. We interpret the results in light of the Pre-semantic Account of Category Effects (PACE; Gerlach, 2009), and conclude that category-effects do not reflect absolute processing differences between categories. Rather, category-effects are products of common operations which are differentially affected by the structural similarity among objects (with natural objects being more structurally similar than artefacts). The potentially most important aspect of the present study is the demonstration that category-effects are very context dependent; an aspect which has been neglected in earlier literature on category-specificity. PACE provides a useful framework in this respect, as it specifies how category-effects are influenced by changes in task and stimulus characteristics.

Delayed processing of global shape information in developmental prosopagnosia

“…We deemed such a relationship likely because recognition of silhouettes and fragmented forms is assumed to place particular demands on global shape processing [38,39]. This prediction was borne out as we find reliable relationships between scores on the GlobalLocal Precedence index and performance with silhouettes and fragmented forms.…”

“…These hypotheses are then used in a top-down manner to augment the buildup of a more detailed description of the stimulus (i.e. shape configuration), which again serves as input for a more specific match with VLTM representations [38,39,44]. The greater the demand placed on perceptual differentiation, the more loops comprising VLTM access !…”

Visual complexity exerts opposing effects on object categorization and identification

“…It has previously been demonstrated that this model can account for how another important object variable (structural similarity) can give rise to opposing effects at different levels of visual object processing (Gerlach, 2009, Gerlach & Toft, 2011. We seek to demonstrate here that the model can also be useful for explaining effects of visual complexity.…”

“…This first pass yields initial hypotheses concerning the likely identity of the stimulus. These hypotheses are then used in a top-down manner to augment the buildup of a more detailed description of the stimulus (i.e., shape configuration), which again serves as input for a more specific match with VLTM representations (Gerlach, 2009;Gerlach & Toft, 2011). The more specific the match criterion is, the more loops comprising shape configuration ↔ VLTM access must be performed in order to obtain sufficient evidence for making a correct classification.…”

“…Until now PACE has primarily been used to account for category effects in visual object recognition; i.e., why natural objects are recognized more efficiently than artefacts in some circumstances but less efficiently than artefacts in other circumstances (Gerlach, 2009;Gerlach & Toft, 2011). The general assumption has been that natural objects and artefacts differ in visual similarity-with natural objects being more visually similar than artefacts-and that visual similarity affects shape configuration and selection differently.…”