The effect of an induced physiological stress response on reading: an eye-tracking study

The perceptual span (PS) is a term used to describe the total visual area from which a person acquires useful information while reading. This area includes the foveal but also part of the parafoveal region. While the foveal input is of high acuity and serves to identify details of the fixated words, the parafoveal one has primarily a preprocessing function. The PS has been shown to be flexible and its size to depend both on the stimulus characteristics (such as text and task properties) and on individual differences. One of the factors that is thought to influence these changes is the systematic shift of attention towards the location of stimuli to be processed before the actual eye movement happens. Attention narrowing is a widely studied phenomenon that shows how stressful events can exert a centralizing effect on attentional resources. Specifically, attention is shifted towards a set of main, central aspects to the task while more peripheral aspects are neglected. Based on this assumption, we conducted a study aiming to investigate whether this effect would also emerge in the case of the PS. Specifically, our hypothesis was that after a stress induction, participants’ attention would be shifted towards the foveal region and that less resources would be available for the parafoveal processing, resulting thus in a smaller PS. We obtained an estimate of the PS’s changes through the contingent-gaze moving window paradigm, using a small- and a big-window conditions. The stress induction was performed by using a hyperventilation technique. We expected to find an interaction between the arousal state (stress induction vs control) and the window size (4 vs 14 rightwards characters). We did not obtain the predicted results as from the analysis of the data did not emerge an interaction between arousal level and window condition. However, we found a main effect of the arousal in two of the measures used as dependent variables. After the stress induction indeed, participants showed a lower average fixation duration and a higher number count of fixation with respect to the control condition. Interestingly, the two effects interpreted together neither reflected an improvement nor a worsening in reading performance in terms of reading speed. A plausible interpretation of these results is provided in the discussion.