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Simulating a route with your index finger: Effect of mental rehearsal on spatial memory

Paper_So Simulating a route with your index finger: Effect of mental rehearsal on spatial memory Wing Chee So (PSYSWC@Nus.Edu.Sg) Department of Psychology, 9 Arts Link National University of Singapore Abstract This paper examines which rehearsal method (physical practice vs. mental practice) can better strengthen spatial memory. Participants were asked to learn four routes that navigated from starting points to destinations in four different maps. Then they were asked to rehearse the routes by using one of the following methods: 1) mental practice by simulating the routes in their mind; 2) physical practice by drawing the routes on papers; 3) physical practice by having index fingers trace the routes in air with eyes closed; and 4) physically practice by having index fingers trace the routes in air with eyes open. Finally, they verbally recalled the routes. The findings showed that physical practice with index fingers tracing the routes in air while keeping the eyes closed outperformed other rehearsal methods. Thus, tracing directions in air without any visual inputs can help participants to retain the visuo-spatial memory. Keywords: Spatial memory; Rehearsal methods; Mental simulation; Navigation; Mental representation Introduction “After you turn left, you go straight and turn right”. When navigating from one place to another in a new environment, we have to find the route, learn the direction, and retain it in our visuo-spatial working memory (VSWM). VSWM is specialized for processing and retaining visual and spatial information (Baddeley & Logie, 1999; Logie, 1995). However, maintenance of visual and spatial information requires rehearsal process. The question of interest is what type of rehearsal method can better strengthen VSWM. One way to rehearse spatial and visual information is to simulate the route in our mental representation, i.e., mental practice. Mentally represented objects and actions share similarities with the actual ones (Kosslyn, Pick, Fariello, 1974; Decety, Jeannerod, & Prablanc, 1989). Previous findings reported that mental practice strengthens memory in learning sport-related activities like dart throwing (Mendoza & Wichman, 1978; Surburg, Sultive, & Porretta, 1995). Mental practice is also found to be effective in enhancing actual performance in athletics (Jones & Stuth, 1997). When learning directions of a route, mental simulation allows us to form a visual image of geometric properties of the layout of the route (e.g., Finke, 1989; Kosslyn, 1980, Shepard & Cooper, 1982). In addition, it activates motor imagery whereby we imagine ourselves tracing the sequence of the direction in our visual imagery (e.g., Barsalou, 1999; Jeannerod, 1995; Kosslyn, Ball, & Reiser, 1978; Parsons, 1987; Shepard & Metzler, 1971). Activation of visual and motor processing can maintain visual and spatial information in working memory. However, mental practice normally does not involve any overt body movements (Richardson, 1967). While we are simulating a route in our mind, we can draw the to-be- remembered route on a paper, i.e., physical practice. Physical practice is an external memory aid that refers to writing down the to-be-remembered information. Previous research found that participants who jogged notes recalled more information than those who did not (FrosterLee, et al., 2005). Yet there is no consensus of whether physical practice is more effective than mental practice. While Intons-Petersons and Fournier (1986) suggested that the use of physical practice resulted in higher recall of words than the use of mental practice, Dyer, Riley, and Yekovich (1979) reported the opposite pattern. Tigner (1999) argued that the combination of physical and mental practices is the best way of rehearsal. The first aim of the present study is to examine whether participants recall directions more accurately when they are performing mental practice, compared to those who are performing physical practice. Other than drawing to-be-remembered route on a paper, we can indeed draw it in air as an alternative form of physical practice. Specifically, we can use our index fingers to trace the route in abstract space. The way we move our hands should reflect the direction of the simulated route in our mental representation (e.g., Hinton & Parsons, 1988; Jeannerod, 1988; Parsons, 1994). To some extent, these hand movements resemble gestures (hand movements that are produced spontaneously when talking). There is abundant evidence showing that gestures reflect individuals’ thoughts and knowledge (Goldin-Meadow, 2003; McNeill, 1992), particularly spatial representation (Hostetter & Hopkins, 2002; Hostetter & Alibali, 2008; but see Wagner, Nusbaum, & Goldin-Meadow, 2004). Previous findings further showed that gestures not only reflect thinking but also bring out implicit knowledge from mental representation during the process of learning (Broaders, et al., 2007). According to this view, using index finger to trace in air makes mental simulation of a route explicit, thereby enhancing spatial memory. The second aim of the present study is to compare the number of directions correctly recalled when participants draw the route on a paper to that when they draw it in air. If tracing the route in air is an effective rehearsal method, then do participants have to track the route in eye gaze when they trace it in air? We do so when we draw the route on a paper in physical practice. One the one hand, visual inputs are important in spatial perception and learning during the