Carrying groceries: More items in early trips than in later trips or the reverse? Implications for pre-crastination.

Returning home from the grocery store with a car full of groceries requires decisions about how many bags to carry when. If the decisions exemplify procrastination, people should carry more bags per trip in late trips than in early trips (putting the hard work off until later), but if the decisions exemplify the recently discovered phenomenon of pre-crastination (Rosenbaum et al. in Psychol Sci 25: 1487-1496, 2014), people should carry more bags per trip in early trips than in late trips (doing the hard work early). To distinguish between these possibilities, we asked university students to carry 5 or 11 dodgeballs from one bin to another 4, 8, 12, or 16 feet away in as many trips as they wished. A random half of the subjects did the tasks with an additional requirement to memorize and then recall 7 digits after carrying all the balls from the home to the target bin. Consistent with pre-crastination, participants carried the most balls per trip in early trips, and consistent with the hypothesis that pre-crastination relates to memory load, the number of balls carried per trip was affected by the presence of a memory load. The results add to the growing evidence for the generality of pre-crastination.

Visuomotor priming of action preparation and motor programming is similar in visually guided and memory-guided actions.

The present study examined whether the planning and execution of a reach-to-grasp movement is susceptible to visuomotor priming, and whether the strength of the priming effect depends on the availability of visual feedback. Participants grasped a target object as quickly as possible with either a whole-hand grip or a precision grip upon hearing an auditory stimulus. Prior to the auditory cue, a prime stimulus was presented. The prime stimulus depicted an object that was either congruent, incongruent, or ambiguous with respect to the required grasp, or it showed no object at all. In addition, participants performed the grasping task in one of three vision conditions: participants' vision was either occluded during both the motor programming and online-control phase (no-vision), participants had vision only during the motor programming phase (partial-vision), or they had vision available throughout task performance (full-vision). Results revealed the presence of two discrete priming effects. First, we found a facilitative effect of congruent compared to incongruent prime-grip combinations that influenced reaction times and kinematic parameters. Second, we found that movements were initiated slower during the no prime compared to all other conditions. However, this effect did not affect movement kinematics. Importantly, the size of both effects was similar regardless of vision. Together, these results suggest that visuomotor priming effects exhibit a similar influence on memory-guided and visually guided actions, indicating the same underlying object representations for those actions, and thus further challenging the real-time view of motor programming. Furthermore, the two different priming effects suggest the presence of functionally distinct, yet related modules or processes related to action preparation and motor programming, and hint towards possible ventrodorsal interactions.