Abstract:

Inhibition of return (IOR) refers to slower responses to targets presented at the previously attended location than to those at control locations. A recent theory suggests that aside from IOR, a mechanism called inhibitory tagging (IT), also works on previously attended locations to temporarily block the perceptual representations accessing its appropriate response. Due to its capability of explaining many complex interactions between IOR and other effects (e.g., the interaction between IOR and Stroop effect), the IT theory has received more and more attention in the recent literature. However, till now, no direct evidence of the dissociation between IOR and IT has been observed in healthy normal participants. In the present study, we tried to dissociate IT from IOR in healthy normal participants by using of a long-term training procedure. 21 healthy participants (2 male, 19 female, with mean age of 22±3.03) were required to finish a task combined the cue-target paradigm and Stroop task in 8 successive days. Specifically, in each training day, the participants were asked to react as fast and accurate as possible to the displayed color of Stroop stimuli (color words) presented at either the cued or uncued locations. Results showed that: 1) the IOR effect decreased significantly as the training days increased in both the traditional RTs difference index (RTcued – RTuncued, p = 0.01) or the RTs ration index (RTuncued /RTcued, p < 0.05). 2) In contrast to the IOR effect, the inhibitory tagging indexed by the interaction between IOR and Stroop effect didn’t show significant decrease with the increased training days. 3) Both the semantic and the response conflict effect expressed a significant decrease trend as the training days extended to 8-days. Taken together, those findings suggest that 1) IT could be dissociated from IOR, providing the first evidence for the dissociation between IT and IOR in heathy participants; 2) IOR could be affected reliably by 8-days training, supporting the “lack of enough training” explanation for the previous inconsistent results about the practice effect of IOR; and 3) at odds with previous studies regarding practice effect of conflict processing (e.g., Chen et al. 2010), the current results suggest that training, at least as long as 8-days training, could affect both the semantic and response conflict.

Key words: Inhibition of return, inhibitory tagging, long-term training