The role of numbers in allocating spatial attention, a parity classification task

It has been proposed that numbers have an effect in allocating spatial attention. In this study I wanted to evaluate the SNARC effect and the proposal that our brain represents numbers in a horizontal mental number line (MNL). In the parity task numbers are relevant for the task but not their magnitude. Participants were requested to classify numbers presented on the screen as even with the right hand and odd with the left hand.

The SSVEP changes in amplitude described that when numbers are relevant for the task, small numbers allocate spatial attention to the left and large numbers allocate spatial attention to the right as described by the SNARC effect and the MNL.

30 subjects participated in the data collection. Data from one subject was 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. Thus, data from 29 participants (12 males, mean age 25.38, two 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, 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.

Participants signed an informed consent document prior to the beginning of the experiment and they were paid for their participation.