Building Bayesian Cognitive Models of Visual Foraging

Foraging entails finding multiple targets sequentially. In humans and other animals, a key observation has been a tendency to forage in `runs' of the same target type. This tendency is context-sensitive, and in humans, it is strongest when the targets are difficult to distinguish from the distractors. Many important questions have yet to be addressed about this and other tendencies in human foraging, and a key limitation is a lack of precise measures of foraging behaviour. The standard measures tend to be run statistics, such as the maximum run length and the number of runs. But these measures are not only interdependent, they are also constrained by the number and distribution of targets, confounding any inferences about the effects of these aspects of the environment on foraging. Moreover, run statistics are underspecified about the underlying cognitive processes determining foraging behaviour. We present an alternative approach: modelling foraging as a procedure of generative sampling without replacement, implemented in a Bayesian multilevel model. This allows us to break behaviour down into a number of biases that influence target selection, such as the proximity of targets and a bias for selecting targets in runs, in a way that is not dependent on the number of targets present. Our method thereby facilitates direct comparison of specific foraging tendencies between search environments that differ in theoretically important dimensions. We demonstrate the use of our model with simulation examples and re-analysis of existing data. We believe our model will provide deeper insights into visual foraging and provide a foundation for further modelling work in this area.

Visual foraging and executive functions: A developmental perspective

In the past few years, interest in visual foraging, where participants search for multiple targets at a time, has increased, as such tasks may provide a richer picture of visual attention than traditional single-target visual search tasks. Little is known about visual foraging in childhood, so we tested 67 6th grade Icelandic children (mean age = 11.80 years, SD = 0.30 years; 36 girls) on a foraging task involving multiple targets of different types, also measuring three subdomains of executive functioning: inhibition, attentional flexibility, and working memory. The foraging results were then compared to findings from a previous study on younger children (66 children aged 4-7 years). The results show that foraging ability improves dramatically between the preschool and middle school years, and that this improvement reflects greater ease with switching between target types. The older children showed foraging patterns previously seen for adults: randomly switching between target templates during feature foraging, but exhaustively foraging for a single target type before switching during conjunction foraging. Younger children, conversely, tended to stick with the same target type for long runs during feature foraging. Switch costs were also much lower for the older children, resulting in faster and more efficient foraging. Lastly, a connection was established between foraging ability and both working memory and attentional flexibility, but not inhibition. Our study shows that foraging is a promising field of study to further our knowledge of visual attention, how it changes throughout the lifespan, and how it is connected to other cognitive functions.

Indirect versus Direct Effects of Freshwater Browning on Larval Fish Foraging

Fish foraging and energy flow between trophic levels are predicted to decline with freshwater browning due to decreased light availability. Studies investigating these predictions have focused on juvenile and adult fishes; however, the larval stage represents a ‘critical period’ in development. We investigated the indirect (i.e., prey availability) versus direct (i.e., visual foraging) effects of browning on zooplankton-larval fish interactions by altering water color with SuperHume (absorbance at 440 nm = 1.6 – 10.8 m-1). Phytoplankton and zooplankton densities were monitored across treatments for one month to simulate the time leading up to fish spawning in the spring. Larval largemouth bass were then introduced to assess indirect effects on fish feeding, growth, and survival. Direct effects on largemouth bass and bluegill foraging on zooplankton were determined with separate short-term experiments. Browning did not directly alter the ability of larvae to capture prey. However, indirect effects on larval fish foraging, growth, and survival were observed as phytoplankton and zooplankton abundance decreased with increased browning. Our data suggest browning may reduce energy transfer to larval fish due to a reduction in prey but not visual foraging.

Do input modalities matter? Speed and reliability of touch inputs and mouse inputs in visual foraging

Visual attention is usually investigated in a variant of the visual search paradigm with a single search target to find in the scene. However, interactions with the natural environment often revolve around more than searching the environment and then executing a single decision. To alleviate these concerns, visual attention researches have recently started exploring the possibility of using touch-screen based foraging tasks. In these tasks, multiple targets have to be cancelled by tapping them. But the adoption remains poor, possibly because of the non-availability of large touch-screen devices in most research institutions. A viable substitute for cancelling targets in such search affordances could be the computer mouse. In the present study, we aimed at investigating how search performance differs in a visual foraging task depending on the input device (touch versus mouse). We presented a visual foraging task for a known target that had to be found multiple times per search display in several search conditions. We found that responses given via mouse are slightly slower in general, but the variances in responses are comparable in all measurements. We did not find disadvantages in using computer mouse in comparison to using a touch screen. We conclude that the computer mouse is an adequate alternative to touch devices and argue that using the computer mouse in visual attention studies should become better adopted.

Dynamics of attentional and oculomotor orienting in visual foraging tasks

A vast amount of research has been carried out to understand how humans visually search for targets in their environment. However, this research has typically involved search for one unique target among several distractors. Although this line of research has yielded important insights into the basic characteristics of how humans explore their visual environment, this may not be a very realistic model for everyday visual orientation. Recently, researchers have used multi-target displays to assess orienting in the visual field. Eye movements in such tasks are, however, less well understood. Here, we investigated oculomotor dynamics during four visual foraging tasks differing in target crypticity (feature-based foraging vs. conjunction-based foraging) and the effector type being used for target selection (mouse foraging vs. gaze foraging). Our results show that both target crypticity and effector type affect foraging strategies. These changes are reflected in oculomotor dynamics, feature foraging being associated with focal exploration (long fixations and short-amplitude saccades), and conjunction foraging with ambient exploration (short fixations and high-amplitude saccades). These results provide important new information for existing accounts of visual attention and oculomotor control and emphasise the usefulness of foraging tasks for a better understanding of how humans orient in the visual environment.