Reduced misinformation effects following saccadic bilateral eye movements Andrew Parker * , Sharon Buckley, Neil Dagnall Manchester Metropolitan University, School of Psychology & Social Change, Hathersage Road, Manchester M13 OJA, United Kingdom article info Article history: Accepted 27 May 2008 Available online 16 July 2008 Keywords: Bilateral eye movements Misinformation effects False memory Hemispheric interaction Source memory abstract The effects of saccadic bilateral (horizontal) eye movements on memory for a visual event narrative were investigated. In the study phase, participants were exposed to a set of pictures accompanied by a verbal commentary describing the events depicted in the pictures. Next, the participants were asked either mis- leading or control questions about the depicted event and were then asked to engage in 30 s of bilateral vs. vertical vs. no eye movements. Finally, recognition memory was tested using the remember–know procedure. It was found that bilateral eye movements increased true memory for the event, increased recollection, and decreased the magnitude of the misinformation effect. The findings are discussed in terms of source monitoring, dual-process theories of memory and the potential neural foundations of such effects. Ó 2008 Elsevier Inc. All rights reserved. 1. Introduction Several independent lines of research have suggested that inter- hemispheric interactions provide an important basis for accurate episodic memory. For example, one line of investigation has made use of individuals for whom interhemispheric processing has been curtailed by the bisection of the corpus callosum. It has been found that performance on tests of episodic memory are typically re- duced compared to tests of semantic or implicit memory (e.g., Cro- nin-Golomb, Gabrieli, & Keane, 1996; Zaidel, 1995). In another set of studies, Propper, Christman, and Phaneuf (2005), argued that mixed (vs. right) handedness is associated with increased hemi- spheric interaction. As a consequence, mixed handed individuals were predicted to show superior performance on episodic tasks. Across two experiments it was found that mixed handed individu- als outperformed right handed individuals both on laboratory based episodic tests and memory for real-world events. Another line of investigation has found that experimental manipulations, which are thought to increase interhemispheric processing, have also enhanced episodic memory. For example, Christman and Propper (2001) presented participants with words to either the right or left hemisphere. Later, memory for these words was tested in either the same (vs. opposite) hemisphere. They found that episodic memory was improved when encoding and retrieval took place in opposite hemispheres. A rather novel and interesting technique, claimed to induce interhemispheric interaction, is saccadic bilateral eye movements (Christman, Gar- vey, Propper, & Phaneuf, 2003). Using this technique, Christman et al. (2003), experiment 1, found recognition memory for words to be improved in terms of an increase in the hit rate and a de- crease in the false alarm rate. Bilateral eye movements have also been shown to reduce the false alarm rate in experimental para- digms that are designed to elicit particularly high rates of false memories. For example, following the study of related words such as thread, pin, eye, sew and sharp, subjects falsely recall and recog- nise associated but non-presented words such as needle (e.g., Roediger & McDermott, 1995). Following thirty seconds of bilateral eye movement, Christman, Propper, and Dion (2004) and Parker and Dagnall (2007), found significant reductions in the false recall and recognition of the non-presented associates. In addition, sacc- adic bilateral eye movements have been found to be related to en- hanced access to earlier childhood memories (Christman, Propper, & Brown, 2006) and the retrieval of associative and contextual information (Parker, Relph, & Dagnall, 2008). Although the precise neural reasons for these results remain to be explored, Christman et al.(2003, 2004) argue that the effects are likely due to increased interhemispheric communication. Their arguments run as follows; Firstly, lateral eye movements lead to increased activation of the contralateral hemisphere (Baken & Svorad, 1969). This appears to be particularly true for, saccadic eye movements which generate more frontal cortical activity compared to smooth pursuit eye movements (O’Driscoll et al., 1998). Secondly, it is presumed that one possible consequence of sequences of right–left eye move- ments is the simultaneous activation of both hemispheres. When equalised activation levels of both hemispheres occur, it is as- sumed that this facilitates hemispheric interaction (see Christman et al., 2003 for discussion of the research relating to this point). Fi- nally, neuroimaging research indicates that episodic memory tends to be associated with bihemispheric activity (e.g., Habib, Nyberg, & Tulving, 2003). Therefore, engaging in saccadic bilateral eye move- ments increases interhemispheric activity and provides a basis for facilitating episodic memory. 0278-2626/$ - see front matter Ó 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.bandc.2008.05.009 * Corresponding author. Fax: +44 01612476842. E-mail address: a.parker@mmu.ac.uk (A. Parker). Brain and Cognition 69 (2009) 89–97 Contents lists available at ScienceDirect Brain and Cognition journal homepage: www.elsevier.com/locate/b&c