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Jan Tünnermann, Anna Schubö; Visual Foraging with Dynamic Stimuli. Journal of Vision 2019;19(10):233c. doi: https://doi.org/10.1167/19.10.233c.
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Foraging is a key behavior in virtually all organisms. In many animals---and especially in primates---foraging is supported by active vision and selective attention. Therefore, computer-based virtual foraging tasks are valuable tools to assess attentional control. In foraging paradigms, participants “harvest” visual elements from limited patches (“berry picking”, cf. Wolfe, 2013) or select elements from multi-element displays containing different target types and distractor elements. When participants have to forage “cryptic” targets (defined by feature conjunctions), they minimize the amount of switching between different target types (Kristjánsson, Jóhannesson, & Thornton, 2014). We extended this visual foraging paradigm by adding dynamic stimuli, which randomly move across a tablet PC screen and have to be collected with a pen. In addition to comparing performance with static and moving displays, we manipulated the ratio of different target types, which becomes possible because of the motion in the display: The complex motion pattern allows to “refill” collected targets without the participants noticing the replacement. In this way, the ratio between two targets types which have to be collected can be held constant or manipulated to assess whether participants make use of different target frequencies. The results show that both static and moving targets defined via simple features led to frequent random switching between target types. Conjunction targets, static or moving, led to longer runs during which the same target type was selected, in agreement with earlier research. Moreover, participants tended to forage the more plentiful target type when target frequencies were manipulated. In sum, our results extend earlier findings of prolonged runs with conjunction targets known from static displays and show that target speed, spatial target distribution, and target ratios can alter attentional strategies as well.
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