Partial Representations of Scenes in Change Blindness: In the Eyes and in the Hands

Partial Representations of Scenes in Change Blindness: In the Eyes and in the Hands Nick Benesh (nbenesh@memphis.edu) Brent Fonville (jbfnvlle@memphis.edu) Rick Dale (radale@memphis.edu) Department of Psychology / Institute for Intelligent Systems University of Memphis Memphis, TN 38152 USA Abstract Change blindness is a person‟s inability to notice changes in a visual scene that seem obvious when pointed out. Recent experiments using eye tracking techniques have suggested that even though participants do not detect a change they fixate on the changing area more. Two studies test whether this finding is present across different change blindness paradigms and whether it is detectable after fixation. In the first study we compare behavior in flicker and gradual change paradigms. Results reveal that across paradigms participants do spend more time on the changing area yet do not detect the change. In the second study we test whether we can capture the traces of change blindness in mouse movement. Findings indicate that accuracy has more of an impact on mouse movement than presence of change. Keywords: change blindness, mouse movement, eye tracking, decision making. Introduction Change blindness occurs when a seemingly obvious occurrence within one's range of vision escapes attention. Many studies have investigated the notion of change blindness. These studies have shown that people fail to see changes in videos, photographs, and even in real life situations about 50% of the time, although these changes are obvious after they have been pointed out (Hollingworth, 2003; Levin, Simons, Angelone, & Chabris, 2002; Rensink, O'Regan, & Clark, 1997; Simons & Chabris, 1999; Simons & Levin, 1997). Evidence for change blindness has been found in both lab and in real life settings and can be induced in various ways (see Rensink, 2002 for an overview). Two of the more common ways to induce change blindness are flicker and gradual changes (Rensink et al., 1997; Simons, Franconeri, & Reimer, 2000). The flicker technique induces change blindness by rapidly presenting two images of the same scene each followed by a blank slide to act as a disruptor (Rensink et al., 1997). The gradual change technique induces change blindness by changing part of the visual scene gradually over a ~12 second viewing time (Simons et al., 2000). David, Laloyaux, Devue, and Cleeremans (2006) compared flicker and gradual change techniques and found that participants were better able to detect changes in flicker videos than in gradual videos, suggesting these two techniques are different and might tap into different perceptual and cognitive processes. Hollingworth, Williams, and Henderson (2001) suggested that change attracts attention. Using a flicker paradigm they found that participants fixated for longer duration on the changing aspect of a scene when they detected the change. More interestingly, they also found participants fixated more on the changing scene even when they did not detect the change. Hollingworth et al. (2001) reported an important finding, because they suggest that change blindness might say more about cognitive processes than visual perceptual processes. Thus far, Hollingworth et al.‟s finding is limited to flicker techniques and might therefore be an artifact of the technique rather than a conclusion for change blindness in general. However, Hollingworth et al.‟s finding has not been investigated for the possibility that cognitive processes might explain the change blindness effect. In this paper, we showcase two studies intending to test whether partial detection of changes may take place even when detection may not occur. The first experiment shows that two commonly used change blindness techniques have similar effects, suggesting that it is not low-level perceptual features that are driving this sub-threshold processing. The second experiment tests whether this processing makes its way to post-viewing decisions, which would shed further light on how detailed these representations are. We first begin with a background summary of action dynamics measures to justify its use in this design. Action Dynamics and Cognition Cognition is not a rigid set of processes, but can be thought of as a continuous, dynamic system that is ever changing from moment to moment. Research in the area of action dynamics has shown that cognitive processes can be tracked at a continuous rate by looking at continuous motor actions such as arm movements (Dale, Roche, Snyder, & McCall, 2008). Rather than using static response measures, the action dynamics approach taps into the evolution of a cognitive process, as it approaches one or another option present in a task environment. Dale, Kehoe, and Spivey (2007) found that arm trajectories differ when competing categories are presented with images of animals. Asking participants to choose the correct category for whale when