Sequential effects modulate spatial biases.

Healthy individuals usually display a bias toward the left side of space. This effect can be measured in a line bisection task or, alternatively, in a landmark task where prebisected lines are presented to participants. Several factors have been shown to influence pseudoneglect, that is, to vary the magnitude of the left side bias. We performed 2 landmark experiments: 1 online (n = 801) and a 2nd in the laboratory (n = 20). Our results demonstrate that pseudoneglect is strongly modulated by the sequence of trials in a landmark task. Of particular relevance is the fact that, for some histories of responses, pseudoneglect is inverted such that apparently there is a preference for the right side. In addition, we show that the way in which the point of subjective equality depends on the previous sequence of trials is well approximated by an exponential filter, well known from the literature of sequential effects to be related to motor control. In other words, the type of sequential effects we encountered in the landmark task is consistent with a purely motor contribution, further deepening our understanding of the way motor control influences pseudoneglect. (PsycINFO Database Record (c) 2017 APA, all rights reserved).