Search strategies improve with practice, but not with time pressure or financial incentives.

Abstract

When searching for an object, do we minimize the number of eye movements we need to make? Under most circumstances, the cost of saccadic parsimony likely outweighs the benefit, given the cost is extensive computation and the benefit is a few hundred milliseconds of time saved. Previous research has measured the proportion of eye movements directed to locations where the target would have been visible in the periphery, as a way of quantifying the proportion of superfluous fixations. A surprisingly large range of individual differences has emerged from these studies, suggesting some people are highly efficient and others much less so. Our question in the current study is whether these individual differences can be explained by differences in motivation. In two experiments, we demonstrate that neither time pressure, nor financial incentive, led to improvements of visual search strategies; the majority of participants continued to make many superfluous fixations in both experiments. The wide range of individual differences in efficiency observed previously was replicated here. We observed small but consistent improvements in strategy over the course of the experiment (regardless of reward or time pressure) suggesting practice, not motivation, makes participants more efficient.

Visual search habits and the spatial structure of scenes

“…The average behaviour of participants searching for the target when the screen is divided in half (whether horizontally or vertically) would suggest no clear preference for the heterogeneous or homogeneous side, but these averages hide clear preferences for one or the other among some individual participants. We have shown previously that these differences are reliable over time (Nowakowska, Clarke, Sahraie, & Hunt, 2019;Nowakowska et al, 2021), making them a useful starting point for investigation using a correlational approach. On the other hand, the behaviour of participants in the jumbled task is more convergent, making the average efficiency score for this specific condition a reasonable representation of the group's behaviour.…”

“…Previous experiments showing a wide range of mostly poor search strategies (Nowakowska et al 2017(Nowakowska et al , 2021 used a display in which the screen was split vertically into left and right halves. This configuration bears little resemblance to how information is distributed in most natural scenes.…”

“…This improvement stands in stark contrast to other manipulations to this task that have not led to improved efficiency. Specifically, Nowakowska et al (2021) varied both the time constraints (untimed versus a 2 s deadline), and reward (a financial incentive to improve reaction time in a second block of trials) and found that neither manipulation improved efficiency. A key difference between that study and this one is that here we have increased efficiency by manipulating the context to better suit the natural search behaviour of the participants.…”

“…We use the data only from target absent trials in calculating this proportion to ensure all fixations are associated with searching for the target (rather than finding or identifying it). We have shown previously that the proportion of heterogeneous-side fixations during the early part of target absent trials is correlated strongly with how quickly targets are found when they are present (Nowakowska et al, 2017;Nowakowska, Clarke, von Seth, & Hunt, 2021).…”

“…Here we divide the search array into upper and lower fields (as opposed to the left/right division used in our previous experiments such as Nowakowska et al (2017Nowakowska et al ( , 2021. If the spatial structure of the visual scene facilitates efficient search, we should see better performance, particularly when the hard (heterogeneous) search is in lower visual field.…”