دیدگاه های جدید در تئوری کنترل توجه

Abstract There have been several theoretical attempts to explain the effects of anxiety on cognitive performance. According to attentional control theory, anxiety impairs the efficiency of two executive functions (the inhibition and shifting functions). Another major theoretical assumption is that anxiety impairs performance effectiveness (the quality of performance) to a lesser extent than processing efficiency (the relationship between performance effectiveness and effort or use of processing resources). However, there may be conditions (e.g., prior presentation of threat-related stimuli) in which that assumption is not applicable. The extensive recent research (including several cognitive neuroscience studies) of direct relevance to the theory is discussed, and suggestions are made for maximizing the value of future cognitive neuroscience research. Finally, attentional control theory is developed to explicate the relationship between anxiety and motivation. Implications for theoretical predictions and alternative theoretical accounts are discussed.

1. Introduction This article is concerned with the effects of individual differences in anxiety on cognitive performance. The emphasis is mainly on anxiety as a personality dimension (i.e., trait anxiety or test anxiety), but the effects of transient anxiety (i.e., state anxiety) are also considered. There is plentiful evidence that anxiety (whether regarded as a personality dimension or as an emotional state) is associated with performance impairments on numerous tasks. A meta-analysis based on hundreds of studies revealed an overall correlation of −0.29 between test anxiety and academic aptitude or achievement (Hembree, 1988). There have been numerous attempts to provide a theoretical explanation for the adverse effects of anxiety on performance. However, we will focus on one particular theoretical approach that has evolved over time. The original statement of the theory was by Eysenck (1979). This was followed by processing efficiency theory (Eysenck & Calvo, 1992), and more recently by attentional control theory (Derakshan and Eysenck, 2009 and Eysenck et al., 2007). It would be superfluous to describe in detail the development of the theory. Instead, we will consider only the major theoretical hypotheses incorporated within processing efficiency theory and attentional control theory (the additional hypotheses associated with attentional control theory are discussed at length in Eysenck et al.). The first major hypothesis forms an important part of processing efficiency theory (Eysenck & Calvo, 1992): anxiety impairs the efficiency of the central executive, which is an attention-like, limited capacity component of the working memory model put forward by Baddeley (1986). In contrast, it was assumed that there are only modest effects of anxiety on the other two components of the original model: (1) the phonological loop (used to rehearse verbal material and to store it briefly) and (2) the visuo-spatial sketchpad (used to process and store transiently visual and spatial information). Much evidence provides support for the first hypothesis in terms of the effects of anxiety on the central executive (see Derakshan & Eysenck, 2009, for a review). However, there are very few studies in which the effects of anxiety on all three components of the working memory model have been compared directly in a single experiment. One such study was carried out by Eysenck, Payne, and Derakshan (2005). Individuals high and low in trait anxiety performed the Corsi Blocks Test concurrently with a secondary task involving the central executive, the phonological loop, or the visuo-spatial sketchpad. Performance on the Corsi Blocks Test was impaired by high trait anxiety when the secondary task involved use of the central executive but not when it involved use of the phonological loop or the visuo-spatial sketchpad. These findings suggested that high anxiety only impaired the functioning of the central executive. Christopher and MacDonald (2005) used a different approach to the same issue. Their participants performed a series of tasks designed to assess different components of the working memory system. The findings closely resembled those of Eysenck et al. (2005): high trait anxiety only impaired performance on those tasks involving the central executive. Walkenhorst and Crowe (2009) used the same general approach as Christopher and MacDonald. They also failed to find any significant effects of trait anxiety on tasks involving the phonological loop or the visuo-spatial sketchpad. However, in contrast to the findings of Christopher and MacDonald, they also reported non-significant effects of anxiety on tasks involving the central executive. The second and third major hypotheses are novel to attentional control theory but developed out of the assumption that anxiety impairs the functioning of the central executive. In short, there is accumulating evidence that various executive functions are associated with the central executive. For example, Miyake et al. (2000) asked their participants to perform numerous executive tasks, and then performed latent-variable analysis to identify the main underlying executive functions. They identified partially independent inhibition, shifting, and updating functions. The inhibition function (subsequently clarified by Friedman and Miyake (2004)) prevents task-irrelevant stimuli and responses from disrupting performance. The shifting function is used to allocate attention in a flexible and optimal way to the task stimulus or stimuli that are currently most relevant. The updating function is used to update and monitor the information currently within working memory. This function is important for various short-term memory tasks. The second hypothesis is that anxiety impairs the functioning of the inhibition function, and the third hypothesis is that anxiety impairs the functioning of the shifting function. The overarching assumption is that anxiety impairs attentional control whether that control is negative (inhibition function) or positive (shifting function). The fourth major hypothesis is based on the distinction between processing efficiency and performance effectiveness, and is incorporated in all versions of the theory from Eysenck (1979) onwards. Performance effectiveness can be defined as the quality of performance (e.g., the percentage of correct task responses). Processing efficiency is defined by the relationship between performance effectiveness and the use of resources or effort. More specifically, processing efficiency is high when performance effectiveness is high and use of resources is low and it is low when performance effectiveness is low but use of resources is high. The crucial hypothesis is that anxiety will typically impair processing efficiency to a greater extent than performance effectiveness. Bishop (2009) agreed with the assumption that anxiety is associated with a broad impairment of attentional control. However, she offered an alternative explanation of the underlying processes. According to her account, individuals high in trait anxiety often exhibit an impoverished recruitment of attentional control mechanisms centered on the dorsolateral prefrontal cortex. This differs from the prediction stemming from attentional control theory, namely, that high anxiety will often be associated with increased activation of brain areas (e.g., dorsolateral prefrontal cortex) associated with attentional control. We have already discussed Hypothesis 1. As a result, we will focus in what follows on the remaining hypotheses.