Browsing by Author "Giesinger, Candice"

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    Can change detection succeed when change localization fails?
    (American Psychological Association, 2020-07-02) Oriet, Chris; Giesinger, Candice; Stewart, Kaiden M.
    Statistical summary representations (SSRs) are thought to be computed by the visual system to provide a rapid summary of the properties of sets of similar objects. Recently, it has been suggested that a change in the statistical properties of a set can be identified even when changes to the individual items comprising the set cannot. Haberman and Whitney (2011) showed that subjects were correctly able to report which of two consecutively presented sets of faces was, on average, happier, even when participants were unable to localize any of the items contributing to this change. In this paper, we revisit this conclusion, and suggest that the results supporting it may be an artifact of the paradigm used. In four experiments we find little evidence to suggest that subjects can reliably detect a change in the average size or emotion of an array of faces when they are unable to localize changes to individual items. The results are well accounted for by assuming that observers are selectively attending to individual items and then inferring the direction of the overall change based on the behaviour of the attended items. We suggest that this occurs because change localization requires focused attention to individual items, impeding calculation of SSRs which requires global attention to the entire set. We conclude that there is currently little evidence that SSRs can facilitate change detection when individual change localization fails.
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    Can perceptual averaging really occur in the absence of change localization?
    (Faculty of Arts, University of Regina, 2017-04-24) Giesinger, Candice
    Noticing the location of an object that causes a change to the mean of a set relies on the ability to determine the mean of the set, and detect that a change has occurred (Rensink, 2002). Previous research suggests that people are able to retain information about the mean emotion of a set of faces even when they are unsure which items changed between the two sets (Haberman & Whitney, 2011). Subjects in that study, however, could use a strategy of localizing the most emotionally extreme face in the set to reliably determine the correct response in the mean discrimination task. In the present study, the utility of this strategy was eliminated. Subjects completed 4 blocks of trials consisting of 48 trials per block. On each trial, subjects viewed two consecutive displays of faces contained within circles. Four items increased (or decreased) in size or emotional intensity. In Experiment 1, subjects first determined whether average size or emotion increased or decreased from the first display to the second, then localized one of the four changed items. In Experiment 2, the order of responding was reversed. The results suggest that when performing both a mean discrimination and localization task, subjects use their knowledge of which stimulus in the set changed to guide their response on the mean discrimination task. Focusing attention to a local region of a display prevents the global distribution of attention necessary for perceptual averaging (Chong & Treisman, 2003). Thus, averaging is not possible when change detection fails.