The role of numbers on spatial attention, a target detection task

<div>In our previous study (the parity judgment task), we provided physiological evidence for the role of numbers in allocating spatial attention as described by the MNL. Here we evaluated whether numbers have an effect in spatial attention when they are not relevant for the task. Participants were requested to ignore the numbers presented on the screen. After the number disappear they should responde if the saw a black box, with the left hand if the box was in the left or the right hand if the box was on the left. </div><div>The SSVEP changes in amplitude described that when numbers are not relevant for the task, small numbers allocate spatial attention to the left but large numbers do not allocate spatial attention to the right as described by the SNARC effect and the MNL. However, when numbers are not part of the task, small numbers allocate attention to the right. </div><div>It seems that depending on the relevance for the task, our brain allocates numbers in a horizontal MNL (parity task) or in what seems to be a vertical MNL (target detection task).</div><div>30 subjects participated in the data collection. Data from four subjects were rejected due to poor behavioral performance. During EEG pre processing, the data from three subjects were rejected due to excessive eye-blink artifacts in more than 30% of the trials and excessive lateral eye movements (i.e., left-right) at the time of target presentation. Finally, during the SSVEP analysis, data from two subjects were rejected due to an absence of visible SSVEP response in the power spectral plots. Thus, data from 25 participants (11 males, mean age 25.04, one left-handed) were included in the final analysis. All subjects had normal or corrected-to-normal vision. The study was conducted in accordance with the Declaration of Helsinki,</div><div>relevant laws, and institutional guidelines, and was approved by the study was approved by the local ethics committee at the Psychology Department at the University of Amsterdam.</div><div>Participants signed an informed consent document prior to the beginning of the experiment and they were paid for their participation.</div>