Academic journal article Perception and Psychophysics

Reorienting Attention and Inhibition of Return

Academic journal article Perception and Psychophysics

Reorienting Attention and Inhibition of Return

Article excerpt

In experiments examining inhibition of return (IOR), it is common practice to present a second cue at fixation during the cue-target interval. The purpose of this fixation cue is to reorient attention away from the cued location to ensure that the facilitative effects of spatial attention do not obscure IOR. However, despite their frequent use, relatively little is known about the relationship between fixation cues and IOR. In the present experiments, we examined the role of fixation cues by manipulating their presence in tasks that either did or did not require target identification. When the participants were required to either detect (Experiment 1A) or localize (Experiment 2A) a target, the magnitude of IOR was unaffected by the presence of a fixation cue. In contrast, when the participants were required to identify a target (Experiments 1B, 2B, and 3), IOR was observed only when a fixation cue was presented. This result was obtained regardless of the type of response that was required (two-alternative forced choice or go/no go). The effectiveness of the fixation cue in revealing IOR in these tasks is consistent with its putative role in reorienting attention away from the cued location.

Covert orienting of attention is often studied within the context of the cue-target paradigm. In this paradigm, the presentation of a spatially uninformative stimulus cue at the location of an upcoming visual target reduces target detection and discrimination reaction time (RT) when the cue-target stimulus onset asynchrony (SOA) is brief (see Wright & Ward, 1998, for a review). This short-lived improvement in performance is believed to result from a reflexive shift of attention to the cued location. At longer SOAs, however, responses to targets at cued locations actually become slower than responses to targets at uncued locations (Posner & Cohen, 1984). Posner, Rafal, Choate, and Vaughan (1985) labeled this later inhibitory effect "inhibition of return" (IOR). Since its discovery, IOR has been observed in a wide variety of experimental situations within the visual, auditory, and tactile modalities, as well as between modalities. IOR has also been observed across a variety of tasks, including detection, localization, and discrimination (see Klein, 2000, for a review). This ubiquity suggests that the mechanisms underlying IOR are important and general processes involved in the spatial selection of information.

Despite extensive research, the exact mechanisms underlying IOR have not yet been determined. When they coined the term "inhibition of return," Posner et al. (1985) proposed that attention is reflexively oriented to the cued location and that, after reorienting to fixation, it is inhibited from returning to a previously attended location. They also suggested that this inhibition of attentional reorienting serves to bias the visual system to acquire novel information at new spatial locations. Although this account of IOR remains popular, competing accounts have also been proposed (for reviews, see Klein, 2000; Taylor & Klein, 1998b, 2000). At present, no consensus has been reached regarding either the mechanisms of IOR or their functional significance. In fact, no consensus has yet been reached regarding which inhibitory cue effects should be classified as IOR. In particular, several authors have proposed that spatial and nonspatial inhibitory effects arise from different mechanisms (Fox & de Fockert, 2001; Prime & Ward, 2002; Taylor & Klein, 1998a). Current evidence indicates that IOR may arise from a combination of inhibited perceptual processing (Handy, Jha, & Mangun, 1999; McDonald, Ward, & Kiehl, 1999; Prime & Ward, 2004, 2006), a more conservative response criterion on valid trials relative to invalid trials (Ivanoff & Klein, 2001), and inhibition of oculomotor programming (Ro, Pratt, & Rafal, 2000). Given the evidence supporting both perceptual and response-related mechanisms, it has been proposed that IOR may arise from multiple mechanisms (Kingstone & Pratt, 1999; Taylor & Klein, 2000). …

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