Academic journal article Attention, Perception and Psychophysics

Task Dependent Modulation of Exogenous Attention: Effects of Target Duration and Intervening Events

Academic journal article Attention, Perception and Psychophysics

Task Dependent Modulation of Exogenous Attention: Effects of Target Duration and Intervening Events

Article excerpt

Abstract Inhibition of return (IOR) consists of slower reaction times in response to stimuli appearing at previously attended or inspected locations. The exact mechanisms underlying the effect have not yet been determined. In the present work, we manipulated two variables, target duration and intervening event (fixation cue between cue and target), through which we modulated the IOR effect as a function of task. When the target was presented until response, the presence of an intervening event made the cueing effect more negative in all tasks, although facilitation in the absence of an intervening event was only observed in discrimination and go-no-go tasks. When the target duration was 50 ms, the effect of the intervening event on cueing was also only observed for the discrimination and go-no-go tasks. Target duration had no effect at all in the discrimination task. Possible mechanisms for these modulations (detection cost and spatial selection benefit, both of which are based on cue-target integration processes) are discussed.

Keywords IOR · Target duration · Intervening event · Fixation cue Task set · Detection cost · Cue-target integration

Attentional orienting is described in the literature as being driven by two mechanisms: endogenous and exogenous orienting (Jonides, 1981). The cost-and-benefit paradigm has been widely used to study these two forms of spatial orienting (Posner, 1980). In this paradigm, a fixation point is presented at the center of a computer screen, with one box being positioned to the left and one to the right of the fixation point. To study endogenous orienting, a central symbolic, spatially informative cue (e.g., an arrow or number) is presented at fixation, predicting the most likely location of an upcoming target. Usually, reaction times (RTs) to targets appearing at the expected location are faster than those to targets presented at the unexpected location, even at long cue-target stimulus onset asynchronies (SOAs; Posner, 1980). This effect is known as facilitation. In contrast, for investigations of exogenous orienting, a spatially uninformative peripheral cue (e.g., a brief flash in one of the boxes) is normally used. This spatial cue does not provide reliable information about the target location (Posner & Cohen, 1984). At short SOAs, RTs are usually faster for targets appearing at the same location as the peripheral cue (i.e., the cued location) than for targets presented at the opposite location (i.e., the uncued location); that is, a facilitatory effect is observed. At longer SOAs, however, the opposite pattern of results emerges: RTs are faster for targets appearing at the uncued as compared to the cued location. This effect, first reported by Posner and Cohen, and named inhibition of return (IOR) by Posner, Rafal, Choate, and Vaughan (1985), was initially thought to reflect a bias against returning attention to previously explored locations (see Klein, 2000; Lupiáñez, Klein, & Bartolomeo, 2006, for reviews). However, although these effects of peripheral cueing were thought to be highly automatic, research has shown that they are modulated by different variables. In fact, the expected results-facilitatory effects at short SOAs (i.e., before attention is disengaged from the cued location) and IOR effects at long SOAs (i.e., after attention is disengaged from the cued location)-are not at all as usual as one might think, and have been shown to depend on many variables, some of which are reviewed below.

Modulation of peripheral cueing effects by task demands

Many studies have found that the magnitude and time course of cueing effects are sensitive to task factors. Lupiáñez and colleagues have consistently demonstrated that facilitation is larger in magnitude in discrimination than in detection tasks. Moreover, IOR emerges at longer cue-target intervals, and is smaller in size, in discrimination than in detection tasks (Lupiáñez, Milán, Tornay, Madrid, & Tudela, 1997; Lupiáñez & Milliken, 1999; Lupiáñez, Ruz, Fîmes, & Milliken, 2007). …

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