Academic journal article Attention, Perception and Psychophysics

Attentional Capture Is Contingent on the Interaction between Task Demand and Stimulus Salience

Academic journal article Attention, Perception and Psychophysics

Attentional Capture Is Contingent on the Interaction between Task Demand and Stimulus Salience

Article excerpt

The aim of this research was to investigate the potential impacts of task demand and stimulus salience on the stimulus-driven attentional capture effect. The participants performed an inefficient visual search task while an irrelevant luminance singleton was present. In Experiment 1, the task demand was manipulated while the stimulus salience of the irrelevant singleton was fixed. With the same salient singleton, the attentional capture effect was observed in the low-difficulty condition but disappeared in the high-difficulty condition. In Experiment 2, the stimulus salience was manipulated while the task demand was fixed. With the same task, the highly salient singleton captured attention, whereas the relatively lowly salient singleton could not. In Experiment 3, both task demand and stimulus salience were manipulated simultaneously. The stimulus-driven attentional capture effect by the irrelevant singleton increased not only as the task demand decreased but also as the stimulus salience increased. The present study might provide a way to reconcile conflicting findings in the attentional capture literature; the underlying neural mechanism is discussed.

It is well known that visual selective attention can be controlled in either a goal-directed or a stimulus-driven manner. When observers are able to orient their attention to objects and events according to their current behavioral goals and intentions, selection is said to be goal-directed, top-down, or endogenous. When attention is involuntarily attracted by specific objects and events irrelevant to the current goals and intentions of observers, selection is said to be stimulus-driven, bottom-up, or exogenous.

Although researchers have been investigating for decades what kind of stimuli have the ability to summon attention in a stimulus-driven fashion, this issue-referred to as attentional capture-is still quite hotly debated (for reviews, see Rauschenberger, 2003a; Simons, 2000). The literature contains three main influential theoretical accounts. First, some researchers have proposed that attention is always captured by the most salient element in the stimulus display, regardless of any top-down modulation (Theeuwes, 1991a, 1992, 1994). Second, some researchers have proposed that only stimuli matching the observer's attentional control setting are capable of capturing attention (Folk, Remington, & Johnston, 1992; Folk, Remington, & Wright, 1994). Third, other researchers have proposed that attentional capture is unique to specific stimulus properties such as abrupt onset (Jonides & Yantis, 1988; Yantis & Hillstrom, 1994; Yantis & Jonides, 1984). However, evidence for each approach is rather mixed. In Theeuwes's studies, the stimulus display usually contained two salient feature singletons, each unique in a different dimension. One singleton defined the target and the other served as the distractor. Theeuwes found that when the distractor was more salient than the target, reaction times (RTs) were elevated, relative to the distractor absence condition. By contrast, when the distractor was less salient, no interference effect was found, so Theeuwes concluded that when search was performed in parallel, attentional allocation depended on the relative bottom-up salience of the elements in the stimulus display, and that top-down selectivity based on target attributes was not possible. However, Bacon and Egeth (1994) claimed that when the target itself was a feature singleton, as in Theeuwes's experiments, the task might be performed using a singleton detection mode, in which the participants simply searched for a discontinuity. Thus, any additional irrelevant singleton could capture attention. When the target was instead specified by a particular value on a feature dimension, the task needed to be performed using a feature search mode, in which the participants searched for the relevant target feature. Thus, a salient distractor could no longer capture attention. …

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