Abstract
In a dynamic and uncertain visual environment, the location with the highest task reward is not always the location with the highest information gain. In such situations, the visual system needs to trade off collecting reward against the risk of missing important events. Here we use a gaze-contingent paradigm in a visual detection task to investigate the learning and planning of temporal eye movement strategies by spatially separating the locations where the uncertainty of obtaining a task reward can be reduced and where the reward can be collected. In three different conditions within the experiment we vary the reward rate to measure subjects’ adaptive behavior in response to these altered task demands. In addition to changing locations using their gaze, subjects completed the same three task conditions by bringing the two separate locations into fixation through a button press instead of a gaze switch. This design allowed comparing the strategies in switching between task reward collection and uncertainty reduction either through gaze switches or through button presses. We find significant differences in switching behavior as function of the three reward rates but also for the two different switching conditions, indicating that humans can adapt their temporal strategies both in response to the obtainable reward rates as well as depending on the switching modality. In order to quantitatively understand the switching behavior, we develop a probabilistic planning model using Partially Observable Markov Decision Processes, which allows inferring participants’ individual behavioral switching costs and perceptual uncertainties. This model reveals that, contrary to a common belief, the subjective internal cost of a gaze switch is quite high, e.g. compared to a manual key press. Our model is able to predict key aspects of subjects’ behavioral data and we conclude that temporal eye movement strategies agree with probabilistic planning under uncertainty.