Attentional momentum does not underlie the inhibition of return effect

J. Pratt, T. M. Spalek, and F, Bradshaw (1999) recently proposed that atten tional momentum is the mechanism underlying the inhibition of return (IOR) effect. They suggested that momentum associated with an attentional movemen t away from a peripherally cued location and toward an uncued opposite loca tion is essential and fundamental to the finding of an IOR effect. Although it is clear from the present study and from a reanalysis of data from Prat t et al. that response time can be facilitated at an uncued opposite locati on, this putative effect of attentional momentum is neither robust nor reli able. First it occurs for only a minority of participants. Second, it occur s in only a subset of the cued display positions. And finally, it is uncorr elated with the occurrence of IOR. Together the data indicate that the atte ntional momentum hypothesis is an overgeneralization and that it does not u nderlie the robust and reliable IOR effect.