Saccade trajectory deviations and inhibition-of-return: Measuring the amount of attentional processing

This study used a classic exogenous cueing task in which an abrupt onset cue indicated the target location at chance level. When there was a delay between the cue and the target, observers responded slower and less accurate to the target presented at cued than at uncued locations, signifying the occurrence of inhibition-of-return (IOR). On some trials, instead of a manual response, participants had to move their eyes to a location in space. Our findings show no saccade deviation away from the location that was inhibited due to IOR unless participants had to process the target letter presented at the inhibited location. Our findings are consistent with the notion that inhibition resulting in IOR does not occur at the saccade map level but IOR seems to reduce the input of signals going into the saccade map. We show that the strength of saccade deviation is an important measure which can reveal the amount of attentional processing taking place at any particular location in time.