Academic journal article Perception and Psychophysics

Task Coordination between and within Sensory Modalities: Effects on Distraction

Academic journal article Perception and Psychophysics

Task Coordination between and within Sensory Modalities: Effects on Distraction

Article excerpt

Load theory predictions for the effects of task coordination between and within sensory modalities (vision and hearing or vision only) on the level of distraction were tested. Response competition effects in a visual flanker task when it was coordinated with an auditory discrimination task (between-modality conditions) or a visual discrimination task (within-modality conditions) were compared with single-task conditions. In the between-modality conditions, response competition effects were greater in the two- (vs. single-) task conditions irrespective of the level of discrimination task difficulty. In the within-modality conditions, response competition effects were greater in the two-task (vs. single-task) conditions only when these involved a more difficult visual discrimination task. The results provided support for the load theory prediction that executive control load leads to greater distractor interference while highlighting the effects of task modality.

It has long been thought that executive control functions associated with the frontal lobe (such as working memory) play a role in goal-directed control of attention (Baddeley, 1996; Desimone & Duncan, 1995). However, behavioral experiments have often failed to show any specific effect of working memory load on performance in attention tasks (e.g., Logan, 1978; Woodman, Vogel, & Luck, 2001; but see Han & Kirn, 2004, and Woodman & Luck, 2004, for exceptions). By contrast with the previous failures, a recent series of studies examining the load theory of attention has provided direct evidence for a specific causal role of executive control in maintaining focused attention on task-relevant stimuli while preventing distraction by task-irrelevant stimuli (de Fockert, Rees, Frith, & Lavie, 2001; Lavie & de Fockert, 2005, 2006; Lavie, Hirst, de Fockert, & Viding, 2004).

Load theory proposes two means of control of selective attention that serve to prevent the processing of irrelevant and potentially distracting stimuli. The first is a fairly passive means of control, whereby task-irrelevant stimuli are simply not perceived when task-relevant processing involves a sufficiently high perceptual load that exhausts perceptual capacity with the perception of task-relevant stimuli. The second is an active means of executive control, whereby the active maintenance of stimulus-processing priorities minimizes distraction by low-priority task-irrelevant stimuli even when these have been perceived (in a situation of low perceptual load that leads to a spillover of capacity and, thus, results in distractor perception). This hypothesis leads to the prediction that when executive control is loaded (e.g., with the need to actively maintain stimuli in an added working memory task or with the need to coordinate swift shifting from one task to another), this should result in greater interference effects by task-irrelevant distractors.

Support for the perceptual mechanism of control hypothesized in load theory has been found in many studies showing elimination of distractor processing in tasks with a high perceptual load (e.g., Lavie, 1995; see Lavie, 2005, for a review). Support for the role of executive control in attention stipulated in load theory has also been found in recent experiments (Lavie, 2000; Lavie & de Fockert, 2005, 2006; Lavie et al., 2004) that have shown that distractor interference effects (measured with response competition effects produced by irrelevant distractors in the flanker task [Eriksen & Eriksen, 1974] or with the attentional capture effects produced by an irrelevant color singleton during a shape-based visual search task) and related visual cortex activity (see de Fockert et al., 2001) were increased when executive control was loaded with an additional working memory task (as compared with low working memory load conditions or with a single-task performance of the selective attention task).

All these experiments involved a working memory task and a selective attention task, and the material presented in both the selective attention and the working memory tasks was visual. …

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