An Experience-Sampling Study of Working Memory and Executive Control in Daily Life

An experience-sampling study of 124 undergraduates, pretested on complex memory-span tasks, examined the relation between working memory capacity (WMC) and the experience of mind wandering in daily life. Over 7 days, personal digital assistants signaled subjects eight times daily to report immediately whether their thoughts had wandered from their current activity, and to describe their psychological and physical context. WMC moderated the relation between mind wandering and activities’ cognitive demand. During challenging activities requiring concentration and effort, higher-WMC subjects maintained on-task thoughts better, and mind-wandered less, than did lower-WMC subjects. The results were therefore consistent with theories of WMC emphasizing the role of executive attention and control processes in determining individual differences and their cognitive consequences. People who differ in cognitive ability, as measured by conventional intelligence tests, have different life experiences. On average, those with higher general intelligence earn better school grades, attain more education, secure more prestigious occupations, are less often killed in automobile accidents, and assume lower incarceration risk than do those with lower intelligence (Gottfredson, 2002). But does cognitive ability predict people’s subjective experience of life events? Personality research suggests that people of higher intelligence are modestly more ‘‘open to experience’’ (aesthetically sensitive, novelty seeking, unconventional, curious) than are people of lower intelligence (Ackerman & Heggestad, 1997). Yet we know of no scientific studies concerning the in-the-moment, dynamic phenomenology of cognitive ability. This is unfortunate because cognitive-mechanistic theories of intelligence, whether emphasizing sensory discrimination, processing speed, or working memory, implicitly predict that variation in these mental systems’ effectiveness should have dramatic consequences for everyday information processing and mental life. Therefore, in the present study, we examined whether working memory capacity (WMC), an important individual differences variable measured in the laboratory, predicts people’s subjective experience of task-unrelated thought, or mind wandering, in daily life. WMC IN THE LABORATORY Researchers often assess WMC with complex span tasks, which present short lists of stimuli for subjects to remember in serial order. These tasks differ from simple span tasks (such as digit span tasks) in that memoranda are presented in alternation with a secondary task (Conway et al., 2005). For example, in a reading span (RSPAN) task, subjects might memorize short lists of letters, with each letter preceded by an unrelated sentence to judge for meaningfulness; in an operation span (OSPAN) task, each letter is preceded by an equation to verify. The insertion of secondary tasks between memory items means that subjects are required to recall information that is periodically unattended (Barrouillet, Bernadin, & Camos, 2004) and vulnerable to proactive interference (Lustig, May, & Hasher, 2001). WMC tasks are of increasing theoretical and practical interest because their scores reliably predict individual differences in many higher-order cognitive abilities, such as comprehension, learning, and fluid intelligence (Barrett, Tugade, & Engle, 2004; Kane, Hambrick, & Conway, 2005). WMC tasks thus measure Address correspondence to Michael J. Kane, Department of Psychology, P.O. Box 26170, University of North Carolina at Greensboro, Greensboro, NC 27402-6170, e-mail: [email protected]. PSYCHOLOGICAL SCIENCE 614 Volume 18—Number 7 Copyright r 2007 Association for Psychological Science something important and general. Engle and Kane (2004) proposed that WMC task performance is influenced by many psychological processes, but its broad prediction of ability derives from domain-general executive-control mechanisms. According to their executive-attention theory, these general control mechanisms principally maintain or recover access to information (stimulus representations or goals) outside of conscious focus, and they are most important in contexts providing concurrent distraction and interference from prior experience. Indeed, people with higher WMC outperform those with lower WMC on attention tasks requiring the active maintenance of novel goals in order to override habitual responding (Kane, Bleckley, Conway, & Engle, 2001). In Stroop tasks, for example, if few trials reinforce the goal to ignore the color words and name their hues (because most words and hues match), low-WMC subjects frequently respond according to habit by reading the words (Kane & Engle, 2003). We have argued that such goal neglect reflects an inability to keep goals consistently active and accessible enough, in the moment, to control thought and behavior according to novel demands. Low-WMC subjects seem to periodically lose focus on their goals, or ‘‘zone out’’ (Schooler, Reichle, & Halpern, 2004), when executive control is challenged.