Supporting the attentional momentum view of IOR: is attention biased to go right?

Inhibition of return (IOR) refers to the finding that individuals are slower to respond to a target presented at a previously attended location than they are to respond to a target presented at a novel location (Posner & Cohen, 1984). The attentional momentum theory is a recent view of how attention moves around the environment, and it provides an account for the IOR effect that does not rely on an inhibitory mechanism (Pratt, Spalek, & Bradshaw, 1999). The present paper supports the attentional momentum viewpoint in two ways: first, by replicating the finding that reaction times to targets at the uncued locations are not all the same (Pratt et al., 1999) and second, by showing that responses made to all locations on the cued side of fixation, and not just to the locations that attention had previously traversed, are slower than are responses made to locations on the opposite side of fixation. We also demonstrate that there is a directional bias to the IOR effect that results in the effect's being larger when attention moves in a left-to-right manner.