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Xiaoli Zhang, Julie Golomb; Localizing visual targets across saccades: Do nontarget landmarks really help?. Journal of Vision 2018;18(10):1287. doi: 10.1167/18.10.1287.
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The image on our retina changes every time we make an eye movement; therefore, it is important to understand how we maintain visual stability across saccades. Specifically, to locate visual targets, we may use nontarget objects as "landmarks". In the current study, we compared how the presence of nontargets (NTs) affects target localization across saccades and during sustained fixation. Participants fixated at a target object, which either maintained its location on the screen (sustained-fixation trials), or displaced to trigger a saccade (saccade trials). After the target disappeared, participants reported the most recent target location with a mouse click. We varied the reference frame in which NTs appeared across saccades: the same locations relative to the target ("Relative"), the same locations relative to the display screen ("Absolute"), or not until the saccade target was presented ("Baseline"). First, we found that the presence of NTs decreased both response error and variability. Interestingly, this NT facilitation effect was the same magnitude for saccade trials and sustained-fixation trials, indicating that NT facilitation might be a general effect on target localization, not specific to saccadic stability. Second, participants' responses were biased towards the NT locations, i.e., the location of spatial references. Both the NT facilitation and NT bias effects were weaker in the Absolute condition compared to the other two conditions, suggesting that the relative spatial relationship between the target and NTs is particularly influential for target localization. Additionally, the initial fixation location and actual saccade landing position also biased target location reports, suggesting that eye movement paths may also be stored as spatial references, and may interact with NTs to influence spatial localization. In summary, the presence of NTs facilitates target localization instead of saccadic stability per se, but it also biases responses, showing that although there is facilitation, it may not be optimal.
Meeting abstract presented at VSS 2018
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