Out of Mind, Out of Sight

Abstract

Mind wandering, in which cognitive processing of the external environment decreases in favor of internal processing (Small-wood & Schooler, 2006), has been consistently associated with errors on tasks requiring sustained attention and continu-ous stimulus monitoring (e.g., Cheyne, Carriere, & Smilek, 2006; Robertson, Manly, Andrade, Baddeley, & Yiend, 1997; Smallwood et al., 2004). Consistent with this finding, recent neuroimaging studies suggest that mind wandering engages the default neural network (Christoff, Gordon, Smallwood, Smith, & Schooler, 2009; Mason et al., 2007; Smallwood, Beach, Schooler, & Handy, 2008; Weissman, Roberts, Viss-cher, & Woldorff, 2006) and is associated with decreased neu-ral analysis of incoming information (Christoff et al., 2009; Smallwood, Beach, et al., 2008; Weissman et al., 2006). Here, we propose that mind wandering also involves overt embodied components whereby external input is blocked at the sensory endings. We demonstrate that during an extended period of reading, episodes of mind wandering, compared with on-task periods, contain more eye closures (blinks) and fewer fixa-tions on the text―even as subjects continue to scan the text.The present investigation is based on the idea that blink rate might serve to modulate trade-offs between attention to mind-wandering thoughts and to external task-related stimuli. Blinks reduce processing of external stimuli in two ways―by physi-cally closing the eyelid and by generating cortical suppression of visual processing both before and after the time of actual lid closure (Bristow, Frith, & Rees, 2005; Bristow, Haynes, Syl-vester, Frith, & Rees, 2005; Ridder & Tomlinson, 1997; Volk-mann, 1986). Increasing the rate of such visual interruptions may facilitate a shift in the balance of processing from exter-nal stimuli to internal thoughts. Consistent with these consid-erations, evidence suggests that an increase in eye blinks is associated with errors in vigilance to external stimuli (Papadelis et al., 2007; Poulton & Gregory, 1952; Van Orden, Jung, & Makeig, 2000) and with conflict between internal and external workload (Recarte, Perez, Conchillo, & Nunes, 2008).To assess the relation between eye blinks and mind wandering, we compared blink rates during probe-caught epi-sodes of mind wandering and on-task periods of reading. Mind-wandering episodes during reading are relatively fre-quent; everyone has experienced interfering thoughts that compromise reading (Reichle, Reineberg, & Schooler, in press; Schooler, Reichle, & Halpern, 2004; Smallwood, McSpadden, & Schooler, 2008), and it is possible to even find oneself at the end of a page with no recollection of having processed the material just “read.” Such