Looking ahead: When do you find the next item in foraging visual search?

Abstract

Many real-world visual tasks involve searching for multiple instances of a target (e.g., picking ripe berries). What strategies do observers use when collecting items in this type of search? Do they wait to finish collecting the current item before starting to look for the next target, or do they search ahead for future targets? We utilized behavioral and eye-tracking measures to distinguish between these two possibilities in foraging search. Experiment 1 used a color wheel technique in which observers searched for T shapes among L shapes while all items independently cycled through a set of colors. Trials were abruptly terminated, and observers reported both the color and location of the next target that they intended to click. Using observers' color reports to infer target-finding times, we demonstrate that observers found the next item before the time of the click on the current target. We validated these results in Experiment 2 by recording fixation locations around the time of each click. Experiment 3 utilized a different procedure, in which all items were intermittently occluded during the trial. We then calculated a distribution of when targets were visible around the time of each click, allowing us to infer when they were most likely found. In a fourth and final experiment, observers indicated the locations of multiple future targets after the search was abruptly terminated. Together, our results provide converging evidence to demonstrate that observers can find the next target before collecting the current target and can typically forage one to two items ahead.

MILO Mobile: An iPad App to Measure Search Performance in Multi-Target Sequences

“…Consistent with the results of Experiment 1, this again verifies that the MILO Mobile app can be used to explore the temporal context of search. More generally, the Shuffle manipulation provides a simple, yet powerful way to modulate the prospective aspects of searching through a sequence by blocking the ability to plan responses in advance (see also Kosovicheva et al, 2020). Previously, we have shown that such planning can occur up to four items ahead in a sequence and takes place during both Vanish and Remain trials (Thornton & Horowitz, 2004).…”

Searching Through Alternating Sequences: Working Memory and Inhibitory Tagging Mechanisms Revealed Using the MILO Task

“…Having to repeatedly update the current search template(s) clearly has implications in terms of WM load, implications that we return to shortly. Our suggestion is that this saw-tooth function, with slow responses followed by fast responses, provides further evidence that participants plan ahead during multiple-item search (Horowitz & Thornton, 2008;Kosovicheva et al, 2020;Thornton & Horowitz, 2004. While searching for the first member of the pair, the location of the second item is either explicitly or implicitly coded, leading to more rapid second response.…”

Inhibitory control deficits in vascular cognitive impairment revealed using the MILO task

“…Such planning is most obvious at the start of the sequence, reflected in a highly elevated first response time compared to all other responses in the sequence (Thornton & Horowitz, 2004;2020a,b;Basoudan et al, 2019). However, using a "shuffle" manipulation, in which the identities --not the locations --of items ahead of the current target are switched in real-time, it has also been shown that such planning occurs up to four items ahead (Thornton & Horowitz, 2004, 2020a; see Kosovicheva et al, 2020 for related findings).…”