Academic journal article Psychonomic Bulletin & Review

Eye Movements Enhance Memory for Individuals Who Are Strongly Right-Handed and Harm It for Individuals Who Are Not

Academic journal article Psychonomic Bulletin & Review

Eye Movements Enhance Memory for Individuals Who Are Strongly Right-Handed and Harm It for Individuals Who Are Not

Article excerpt

Subjects who make repetitive saccadic eye movements before a memory test subsequently exhibit superior retrieval in comparison with subjects who do not move their eyes. It has been proposed that eye movements enhance retrieval by increasing interaction of the left and right cerebral hemispheres. To test this, we compared the effect of eye movements on subsequent recall (Experiment 1) and recognition (Experiment 2) in two groups thought to differ in baseline degree of hemispheric interaction-individuals who are strongly right-handed (SR) and individuals who are not (nSR). For SR subjects, who naturally may experience less hemispheric interaction than nSR subjects, eye movements enhanced retrieval. In contrast, depending on the measure, eye movements were either inconsequential or even detrimental for nSR subjects. These results partially support the hemispheric interaction account, but demand an amendment to explain the harmful effects of eye movements for nSR individuals.

Recent research suggests a surprising way to enhance retrieval on a memory test: repeatedly move one's eyes left and right before the test. In comparison with subjects who kept their eyes still for 30 sec immediately before test, subjects who made repetitive, horizontal saccadic eye movements for an equal duration exhibited more accurate recognition (Christman, Garvey, Propper, & Phaneuf, 2003, Experiment 1; Parker & Dagnall, 2007) and recall (Christman, Propper, & Dion, 2004, Experiment 2) of word lists (see also Christman et al., 2003, Experiment 2).

Why do horizontal saccades enhance retrieval? Citing evidence that lateral saccades produce sustained activation of the contralateral hemisphere (Bakan & Svorad, 1969), Christman et al. (2003) proposed that alternating left-right movements increase bihemispheric activation, which leads to greater or more efficient hemispheric interaction, which in turn benefits retrieval. At present, there is little direct evidence that bilateral saccades increase hemispheric interaction (but see Propper, Pierce, Bellorado, Geisler, & Christman, 2007), but, if they do, there is theoretical and empirical cause to believe it would enhance retrieval. Theoretically, complex retrieval tasks such as free recall and difficult recognition tests are thought to depend on hemispheric interaction (Johnson & Raye, 2000) because they simultaneously activate regions in both left and right prefrontal cortex (Nolde, Johnson, & Raye, 1998). Empirically, greater hemispheric interaction has been linked to superior retrieval in comparisons of groups that differ in such interaction. For example, individuals with intact hemispheric commissures show better retrieval than do split-brain patients (Phelps, Hirst, & Gazzaniga, 1991; Zaidel & Sperry, 1974). More germane to the present investigation, neuroanatomical findings suggest that individuals who are strongly right-handed (SR) may experience less hemispheric interaction than individuals who are not (nSR) because the major pathway for interaction-the corpus callosum-is smaller in the former than in the latter (Cowell, Kertesz, & Denenberg, 1993; Habib et al., 1991; Witelson, 1985; but for failures to find differences, see Jäncke & Steinmetz, 2003; Kertesz, Polk, Howell, & Black, 1987). Accordingly, recent studies have documented inferior explicit memory in SR versus nSR individuals (Christman, Propper, & Brown, 2006, Experiment 1; Christman et al., 2004, Experiment 1; Lyle, McCabe, & Roediger, in press; Propper, Christman, & Phaneuf, 2005).

If eye movements enhance retrieval by increasing hemispheric interaction (Christman et al., 2003), then the manipulation should differentially affect groups that differ in baseline interaction. A group with less interaction, like SR individuals, may benefit from eye movements more than a group with greater interaction, like nSR individuals, because members of the former group have a larger margin for increases in interaction. …

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