Influence of stimulus type on effects of flanker, flanker position, and trial sequence in a saccadic eye movement task

Abstract

Using the flanker paradigm in a task requiring eye movement responses, we examined how stimulus type (arrows vs. letters) modulated effects of flanker and flanker position. Further, we examined trial sequence effects and the impact of stimulus type on these effects. Participants responded to a central target with a left- or rightward saccade. We reasoned that arrows, being overlearned symbols of direction, are processed with less effort and are therefore linked more easily to a direction and a required response than are letters. The main findings demonstrate that (a) flanker effects were stronger for arrows than for letters, (b) flanker position more strongly modulated the flanker effect for letters than for arrows, and (c) trial sequence effects partly differed between the two stimulus types. We discuss these findings in the context of a more automatic and effortless processing of arrow relative to letter stimuli.

Keywords:

• Flanker interference
• Cognitive conflict
• Saccades
• Involuntary processing
• Attention

We would like to thank Anna Maria Benedykcinska for her support with data collection and Ion Victor Gosea for programming the experiment. Further we would like to thank Ines Jentzsch, James R. Schmidt, and an anonymous reviewer for their very constructive comments.

Notes

¹ We are providing the actual SRTs in ms for a better illustration of the results.

² Previous studies that also utilized arrow stimuli but in which manual responses had to be given (e.g., Mayr et al., 2003; Nieuwenhuis et al., 2006) reported, for instance, Gratton effects. Thus, also for arrow stimuli, information from one trial can in principle persist into the next one. Critically, this pattern of results may be affected by response mode.