Abstract
Craighero et al (Neuroreport 8, 1996, 347–349) demonstrated that grasping can be primed by previously viewing a bar in the same orientation as the goal object. However, because participants could not see the object they were grasping, it is not clear that the effects on reaction time should be construed as evidence for visuomotor priming (as the authors contend), or are simply due to the priming of a memory-driven movement (i.e., grasping of an unseen target). Therefore, in Experiment 1, we directly compared priming of memory-guided and visually-guided grasping using a paradigm similar to Craighero et al. We found that only memory-guided grasping showed evidence of priming. In Experiment 2, we used a more conventional priming paradigm to compare the effects of priming on both grasping and naming of a novel probe object. Prime and probe objects varied in orientation (same/different) and/or shape (same/different). Participants were faster to name the probe when its shape was the same as the prime. We were confident, therefore, that our paradigm could reproduce standard repetition priming effects on naming. Nevertheless, reaction time for grasping was unaffected by the orientation or the shape of the prime. In Experiment 3, participants reached to grasp a probe object after first viewing or grasping a prime. Reaction time for grasping again remained unaffected in both tasks. Taken together, these results suggest that the initial programming of visually-guided grasping is determined more by what is on the retina than by what is in memory.