Academic journal article Perception and Psychophysics

Context Influences Holistic Processing of Nonface Objects in the Composite Task

Academic journal article Perception and Psychophysics

Context Influences Holistic Processing of Nonface Objects in the Composite Task

Article excerpt

We explored whether holistic-like effects can be observed for nonface objects in novices as a result of the task context. We measured contextually induced congruency effects for novel objects (Greebles) in a sequential matching selective attention task (composite task). When format at study was blocked, congruency effects were observed for study-misaligned, but not study-aligned, conditions (Experiment 1). However, congruency effects were observed in all conditions when study formats were randomized (Experiment 2), revealing that the presence of certain trial types (study-misaligned) in an experiment can induce congruency effects. In a dual task, a congruency effect for Greebles was induced in trials in which a face was first encoded, but only when it was aligned (Experiment 3). Thus, congruency effects can be induced by context that operates at the scale of the entire experiment or within a single trial. Implications for using the composite task to measure holistic processing are discussed.

It is generally accepted that faces are processed differently from other objects (Farah, Wilson, Drain, & Tanaka, 1998; Ge, Wang, McCleery, & Lee, 2006; Maurer, Le Grand, & Mondloch, 2002; Yin, 1969; but see Sekuler, Gaspar, Gold, &, Bennett, 2004; Wenger & Ingvalson, 2002). More specifically, face processing is believed to be holistic: Faces are processed as unified wholes rather than in terms of parts or features. A holistic processing strategy for faces is highly adaptive: Since all faces are made up of the same features in the same configuration, it is the subtle differences in the spatial relations between these features that are diagnostic of identity (Diamond & Carey, 1986; Leder & Bruce, 1998, 2000; Le Grand, Mondloch, Maurer, & Brent, 2004; Mondloch, Le Grand, & Maurer, 2002; Searcy & Bartlett, 1996). However, one negative consequence of this holistic processing strategy is that participants are unable to selectively attend to one part of a face, even when a failure to do so negatively impacts their performance in an experimental task (e.g., Farah et al., 1998; Richler, Tanaka, Brown, & Gauthier, 2008). Although evidence suggests that holistic processing of faces is relatively robust, here, we investigated the possibility that similar effects can also be found with nonface objects because of contextual influences. First, we describe the measure of holistic processing used in our studies, and then outline what motivated us in searching for contextually induced effects that would resemble hallmarks of holistic processing.

One paradigm that is used to assess failures of selective attention due to holistic processing is the composite task. In this task, participants are asked to match one half of a study face composite, made of the top of one face and the bottom of another, to the corresponding half of a subsequently presented test face composite. On congruent trials, both the relevant and irrelevant parts of the test face are the same as or different from the corresponding parts of the study face; on incongruent trials, one part is the same and the other part is different. Holistic processing is inferred from a congruency effect, in which performance is impaired on incongruent trials relative to congruent trials; the information in the irrelevant face half interferes with performance, despite instructions to selectively attend to the relevant half (Cheung, Richler, Palmeri, & Gauthier, 2008; Farah et al., 1998; Gauthier, Curran, Curby, & Collins, 2003; Richler, Gauthier, Wenger, & Palmeri, 2008; Richler, Tanaka, et al., 2008). Importantly, the congruency effect is larger for faces than for other objects (Farah et al., 1998) and increases with perceptual expertise (Gauthier & Tarr, 2002).

Often, studies using the composite task also use an alignment manipulation. The standard finding is that the congruency effect is reduced when the face halves are misaligned at test; when the face halves are no longer presented in the meaningful arrangement, holistic processing is attenuated (Cheung et al. …

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