Eliminating Individual Differences in Distractibility With Load

Perceptual load has been found to be a powerful determinant of distractibility in laboratory tasks. The present study assessed how the effects of perceptual load on distractibility in the laboratory relate to individual differences in the likelihood of distractibility in daily life. Sixty-one subjects performed a response-competition task in which perceptual load was varied. As expected, individuals reporting high levels of distractibility (on the Cognitive Failures Questionnaire, an established measure of distractibility in daily life) experienced greater distractor interference than did individuals reporting low levels. The critical finding, however, was that this relationship was confined to task conditions of low perceptual load: High perceptual load reduced distractor interference for all subjects, eliminating any individual differences. These findings suggest that the level of perceptual load in a task can predict whether individual differences in distractibility will be found and that high-load modifications of daily tasks may prove useful in preventing unwanted consequences of high distractibility. The ability to ignore irrelevant distracting stimuli is of great relevance for everyday life, as the effects of distraction on behavior can have a range of consequences, some that are detrimental (e.g., during driving) and some that simply detract from the quality of life (e.g., during reading). It is therefore important to examine how attention theories that prescribe determinants of focused attention (and, conversely, distractibility) relate to people’s ability to ignore irrelevant distractors when focusing attention on relevant information in daily life. The load theory of attention suggests that a major determinant of focused attention and the ability to ignore irrelevant distractors is the level of perceptual load in the current task (e.g., Lavie, 1995; Lavie, Hirst, De Fockert, & Viding, 2004). Although irrelevant distractors interfere with performance on tasks of low perceptual load (e.g., involving just one relevant stimulus), such distractor interference is eliminated on tasks of higher perceptual load (e.g., involving six or more stimuli; see Lavie, 2005, for a review). To examine how this theory relates to distractibility in everyday life, we assessed how the effects of perceptual load on an individual’s magnitude of distraction in the laboratory relate to the extent to which the individual is likely to be distracted in daily life. The latter was measured with the Cognitive Failures Questionnaire (CFQ; Broadbent, Cooper, FitzGerald, & Parkes, 1982), the most established measure for individual differences in distractibility in everyday life. Subjects performed a typical perceptual-load-plus-distractor task (e.g., Lavie, 1995; Lavie & Cox, 1997; Lavie & Fox, 2000) that required them to search for one of two target letters in displays of either low perceptual load (an angular target letter among five Os) or high perceptual load (an angular target letter among five angular nontarget letters). An irrelevant peripheral distractor letter was also present in each display, and subjects tried their best to ignore it. The irrelevant distractor was either the same as the search target in the display (compatible conditions) or the same as the other search target (incompatible conditions). Distractor-compatibility effects on reaction times (RTs) were our measure of the extent to which people were distracted. Subjects’ magnitude of distraction under conditions of low and high perceptual load was related to their CFQ scores. The CFQ Address correspondence to Nilli Lavie, Department of Psychology, University College London, Gower St., London WC1E 6BT, United Kingdom, e-mail: [email protected]. PSYCHOLOGICAL SCIENCE Volume 18—Number 5 377 Copyright r 2007 Association for Psychological Science requires respondents to rate the frequency with which they experience 25 common types of cognitive failures. For example, the questionnaire asks, ‘‘How often do you start doing one thing at home and get distracted into doing something else (unintentionally)?’’ and ‘‘How often do you find you accidentally throw away the thing you want and keep what you meant to throw away—as in the example of throwing away the matchbox and putting the used match in your pocket?’’ CFQ scores correlate significantly with ratings of respondents by their spouses (Broadbent et al., 1982). Moreover, CFQ scores remain stable over time (Broadbent et al., 1982) and may even reflect a genetic predisposition, as the correlation of CFQ scores is around .5 between monozygotic twin pairs but drops to around .25 for dizygotic twin pairs and .2 for parent-offspring pairs (Boomsma, 1998). High CFQ scores have been associated with increased frequency of car accidents (Larson & Merritt, 1991), injuries from falling (Larson, Alderton, Neideffer, & Underhill, 1997), and accidents at work among electrical workers (Wallace & Vodanovich, 2003), as well as with a clearly less detrimental failure but nonetheless one that detracts from quality of life: losing work through failure to regularly save files when using a computer (Jones & Martin, 2003). These consequences of high distractibility suggest that it is highly important to ask whether high perceptual load can prevent distraction for all people, even those who are highly distractible and are particularly likely to be involved in various accidents. To address this question, it was first important to establish that individual differences in the likelihood of daily-life distractibility relate to the magnitude of distraction in our laboratory task. Specifically, we expected that people with high scores on the CFQ measure of daily-life distractibility would exhibit greater distractor effects in our task than would people with low CFQ scores. Our key prediction, however, concerned the effect of perceptual load on these individual differences. If high perceptual load can eliminate distraction for all people, then individuals with high CFQ scores, compared with those with low CFQ scores, would be expected to show greater interference from the irrelevant distractor in conditions of low perceptual load but not in conditions of high perceptual load.