Cognitive Heuristics Can Be More Important Than Biomechanics In Human Action Planning: The Near Object Effect In Walking And Reaching

Open Access
Gong, Lanyun
Graduate Program:
Master of Science
Document Type:
Master Thesis
Date of Defense:
May 21, 2012
Committee Members:
  • David A. Rosenbaum, Thesis Advisor
  • cognitive heuristics
  • walking
  • reaching
  • movement selection
The coordination of walking and reaching has received remarkably little attention in the study of motor control. Among the few studies that have been done on this topic, very few have explored macroscopic decision-making about walking-and-reaching paths. To shed light on this topic, I asked participants to choose between picking up a bucket on the left and picking up a bucket on the right to carry the picked-up bucket to a left or right platform equally far (16 feet) from the participant’s starting position. The left and right buckets stood 2 feet, 4 feet, 6 feet, or 8 feet from the participant’s starting position and were tested in all possible combinations. In Experiment 1-3, I found that participants did something surprising: When the two buckets were different distances from the starting position, participants picked up the nearer bucket even though that meant they had to carry it farther. This result held up regardless of whether the bucket was light or heavy (even as heavy as 7 lbs). In Experiment 4, I reversed the bucket locations to the second half of the walking path, so the buckets stood 2 feet, 4 feet, 6 feet, or 8 feet away from the ending position, not the starting position. With this arrangement, I found that the number of participants who chose the near bucket did not exceed the number of participants who chose the far bucket, in contrast to what I found in Experiments 1, 2 and 3, where there was a strong near-bucket preference. In Experiment 5, I found that participants picked up the near bucket to minimize pre-lift distance rather than to maximize post-lift distance. Collectively, these results suggest that some cognitive factor was taken into account that offset the cost of carrying the bucket farther. More broadly, the results indicate that a simple view of biomechanical cost reduction for action selection is insufficient. Cognitive factors must also be taken into account.