Abstract
Purpose: Previous research by Guenther & Brown (VSS 2007) manipulated the relative balance of P and M activity finding relatively greater P activity to be associated with increased IOR and relatively greater M activity to be associated with decreased IOR. To further examine the roles of the P and M pathways in location-based IOR, the present research employed abrupt versus ramped stimulus presentations to manipulate the relative balance of P and M activity. It was predicted that since ramped stimuli would be processed less efficiently by the M system, ramped and abrupt stimuli would represent conditions of relatively less M (i.e., greater P) and relatively greater M activity respectively. Method: Cue and target onsets and offsets were either abrupt or ramped. They were presented either alone, in 2-D, or in 3-D objects, using timing parameters known to produce location-based IOR. Simple RT to target onset was measured. Results: Ramping had the expected sensory effects of reducing the M response as indicated by the increased RTs to ramped compared to abrupt targets. Direct RT comparisons of abrupt and ramped conditions were validated through a control experiment. Without objects, ramped and abrupt conditions produced similar IOR. With both 2-D and 3-D objects, IOR differences emerged with greater IOR to the relatively more P based, ramped condition and less IOR to the relatively more M based, abrupt condition. Conclusions: While SF appears to be a better way to produce P and M based differences in IOR (Guenther & Brown, VSS 2007), the interaction of abrupt vs. ramped presentation conditions with 2-D and 3-D objects supports the association of relatively greater P/ventral activity with increased IOR.