Abstract
Attention improves processing of targets and can be engaged with or without the intention to attend to a specific stimulus. Recent work has shown that predictive central arrow cues, that have frequently been used to estimate effects of volitional orienting, trigger an interaction of reflexive and volitional orienting. The obtained effects are larger than the sum of reflexive and volitional orienting. Based on these findings an interaction principle has been postulated, stating that when cues that elicit reliable reflexive orienting are made spatially predictive, the resulting attention effects will be greater than the sum of the effects produced by reflexive and volitional orienting. Two experiments were designed to further test this principle. Experiment 1 assessed how reliable central arrow cues have to be in order to produce the interaction. The degree of predictability was varied systematically and the effects of central arrow cues (volitional and reflexive orienting) were compared to the effects of central number cues (volitional orienting). The results showed that central numbers had to be highly predictive for cueing effects to occur, confirming that orienting to these cues was volitional in nature. For central arrows cueing effects emerged at all predictability levels, increased gradually with increasing predictability, and importantly, exceeded those of central numbers, also when corrected for their reflexive component. Experiment 2 tested whether enhanced attention effects of central arrow cues are also evident in comparison to yet another central cue that measures volitional orienting: colour. The results showed that cueing effects triggered by predictive arrows, also when corrected for their reflexive component, exceeded those of predictive colour cues. In summary, both experiments verified the enhanced attention effects predicted by the interaction principle.