Academic journal article Cognitive, Affective and Behavioral Neuroscience

Electrodermal Responses to Sources of Dual-Task Interference

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Electrodermal Responses to Sources of Dual-Task Interference

Article excerpt

Abstract There is a response selection bottleneck that is responsible for dual-task interference. How the response selection bottleneck operates was addressed in three dual-task experiments. The overlap between two tasks (as indexed by the stimulus onset asynchrony [SOA]) was systematically manipulated, and both reaction time and electrodermal activity were measured. In addition, each experiment also manipulated some aspect of the difficulty of either task.Both increasing task overlap by reducing SOA and increasing the difficulty of either task lengthened reaction times. Electrodermal response was strongly affected by task difficulty but was only weakly affected by SOA, and in a different manner from reaction time. A fourth experiment found that the subjectively perceived difficulty of a dual-task trial was affected both by task difficulty and by SOA, but in different ways than electrodermal activity. Overall, the results were not consistent with a response selection bottleneck that involves processes of voluntary, executive attention. Instead, the results converge with findings from neural network modeling to suggest that the delay of one task while another is being processed reflects the operation of a routing mechanism that can process only one stream of information for action at a time and of a passive, structural store that temporarily holds information for the delayed task. The results suggest that conventional blocked or event-related neuroimaging designs may be inadequate to identify the mechanism of operation of the response selection bottleneck.

Keywords Electrodermal activity * Electrodermal response * Skin-conductance response * Dual-task interference * Psychological refractory period

Introduction

A widely held view is that humans are able to multitask effectively-that is, to successfully carry out two simultaneous tasks, such as conversing and driving an automobile. The empirical, scientific evidence clearly shows this to be false; performance on one or both tasks is degraded (in the instance of driving, see, e.g., Levy, Pashler, & Boer, 2006; Strayer & Drews, 2007). There are three principal questions to be asked about dual-task interference: What are the behavioral results of the interference? Where does the interference occur in the brain? How does the interference operate? The behavioral nature of the interference as seen in task reaction times (RTs) is well understood. Under most circumstances in which two tasks overlap, central processing (such as response selection) on one task must be halted until central processing on the other task is completed (see Pashler, 1994, 1998, for reviews). Concerning brain localization, studies using neuroimaging converge in implicating a neural substrate that is somehow involved with dual-task interference and that involves lateral and medial frontal mechanisms interacting with parietal mechanisms (for a review, see Marois & Ivanoff, 2005). Concerning how dual-task interference operates, we will first outline two competing explanations, and then we will use electrodermal activity (EDA) as the dependent measure to assess those explanations. Finally, we will consider the implications of the results for neuroanatomical models of dual-task processing.

The nature of dual-task interference: Behavioral studies

The experimental approach that gives the greatest analytical leverage in understanding dual-task interference is to present two distinct stimuli whose onsets are separated by a systematically manipulated stimulus onset asynchrony (SOA) and that require two distinct, speeded responses. A large number of behavioral experiments have shown that under a very wide range of circumstances as the overlap between the first and second tasks increases-that is, as the SOA shortens-the RT to complete the second of the two tasks systematically lengthens (for reviews, see Pashler, 1994, 1998). This task 2 RT lengthening with decreasing SOA is called the psychological refractory period (PRP) effect (Vince, 1948; Welford, 1952), by analogy with the refractory period when a neuron is unresponsive to stimulation after an immediately preceding action potential (Marey, 1876). …

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