Academic journal article Attention, Perception and Psychophysics

Temporal Buffering and Visual Capacity: The Time Course of Object Formation Underlies Capacity Limits in Visual Cognition

Academic journal article Attention, Perception and Psychophysics

Temporal Buffering and Visual Capacity: The Time Course of Object Formation Underlies Capacity Limits in Visual Cognition

Article excerpt

Published online: 9 April 2013

© The Author(s) 2013. This article is published with open access at Springerlink.com

Abstract Capacity limits are a hallmark of visual cognition. The upper boundary of our ability to individuate and remember objects is well known but-despite its central role in visual information processing-not well understood. Here, we investigated the role of temporal limits in the perceptual processes of forming "object files." Specifically we examined the two fundamental mechanisms of object file formation-individuation and identification-by selectively interfering with visual processing by using forward and backward masking with variable stimulus onset asynchronies. While target detection was almost unaffected by these two types of masking, they showed distinct effects on the two different stages of object formation. Forward "integration" masking selectively impaired object individuation, whereas backward "interruption" masking only affected identification and the consolidation of information into visual working memory. We therefore conclude that the inherent temporal dynamics of visual information processing are an essential component in creating the capacity limits in object individuation and visual working memory.

Keywords Object individuation · Object identification · Sensory memory · Visual working memory · Capacity · Visual masking

(ProQuest: ... denotes formulae omitted.)

One of the fundamental goals of perception is to enable us to interact with objects in the environment. According to Wundt, the interaction of an observer with the external environment (the "psychophysical process") can be subdivided into three temporally successive and distinct stages (Wundt, 1899, 1900). The first stage ("perception") describes the entrance of an object into the field of vision, allowing it to be detected. In a subsequent stage, termed "apperception," the perceived object occupies the focus of the observer's attention. Finally, the observer develops the volition to react to the object, either cognitively, by storing it into memory, or behaviorally, with a grasping or a saccadic eye movement.

Wundt's description emphasizes how object recognition involves a temporal succession of distinct processing stages - from an unlimited in capacity, but fragile, purely bottom-up and in parallel computed sensory representation (iconic memory: Neisser, 1967; Sperling, 1960, 1963) to a capacity limited, durable and cognitively structured visual store (visual short-term memory: Phillips & Baddeley, 1971; Sperling, 1960, 1963) leading to an action that results in an isomorphic one-to-one relation between observer and object.

As is shown in Fig. 1A, Wundt's stage of apperception can be further subdivided into two processing mechanisms: object individuation and object identification (Xu & Chun, 2009). Individuation involves selecting features from a crowded scene, binding them into a unitary representation, and individuating this spatiotemporal unit from other objects in the image (Kahneman, Treisman, & Gibbs, 1992; Pylyshyn, 1989; Treisman & Gelade, 1980; Xu & Chun, 2009). Object representations at this stage are suggested to be coarse and contain only minimal feature information (Xu & Chun, 2009). Some of these "object files" (Kahneman et al., 1992) are elaborated subsequently during object identification. It is at this stage that identity information becomes available to the observer, and the content of the object files can be consolidated into durable and reportable representations in visual working memory. The number of objects available at this stage is variable, depending on the object complexity, task demands, and representation resolution (Alvarez & Cavanagh, 2004; Xu & Chun, 2009). As individuation precedes identification, the capacity of the latter has its upper bound at the limit of the former (Dempere-Marco, Melcher, & Deco, 2012; Melcher & Piazza, 2011; Piazza, Fumarola, Chinello, & Melcher, 2011). …

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