Date Published: July 10, 2017
Publisher: Public Library of Science
Author(s): Magdalena Ewa Król, Michał Król, Andreas B Eder.
Predictions optimize processing by reducing attentional resources allocation to expected or predictable sensory data. Our study demonstrates that these saved processing resources can be then used on concurrent stimuli, and in consequence improve their processing and encoding. We illustrate this “trickle-down” effect with a dual task, where the primary task varied in terms of predictability. The primary task involved detection of a pre-specified symbol that appeared at some point of a short video of a dot moving along a random, semi-predictable or predictable trajectory. The concurrent secondary task involved memorization of photographs representing either emotionally neutral or non-neutral (social or threatening) content. Performance in the secondary task was measured by a memory test. We found that participants allocated more attention to unpredictable (random and semi-predictable) stimuli than to predictable stimuli. Additionally, when the stimuli in the primary task were more predictable, participants performed better in the secondary task, as evidenced by higher sensitivity in the memory test. Finally, social or threatening stimuli were allocated more “looking time” and a larger number of saccades than neutral stimuli. This effect was stronger for the threatening stimuli than social stimuli. Thus, predictability of environmental input is used in optimizing the allocation of attentional resources, which trickles-down and benefits the processing of concurrent stimuli.
The purpose of attention is to select information from the environmental input for further processing, based on the trade–off between maximization of information utility and minimization of costs related to information processing. This process of information selection is subject to a significant “budget constraint”, as the brain’s processing capacity is limited [1,2] and the metabolic cost of cortical computations is high . Therefore, it would not be optimal to spend our limited processing capacity on information with low utility.
The main goal of the study was to investigate whether predictability of the primary stimulus leads to a reduction in attentional resources allocation to that stimulus and, as a consequence, frees the resources for the processing of concurrent stimuli. This in turn should lead to more in-depth processing of the secondary stimulus, reflected in more robust encoding and better future recollection of that stimulus. This hypothesis was operationalized using a dual-task and testing the influence of stimulus predictability in the primary task on the attention allocation and performance in both tasks. Additionally, we wanted to test whether stimuli particularly important from evolutionary point of view, will be capable of distorting the allocation of attention driven by stimulus predictability. We used eye-movement patterns as the measure of visual attention allocation. We also performed signal detection analysis (where possible) and analysed the accuracy of responses in both primary and secondary tasks.