Reaching while walking: reaching distance costs more than walking distance.

Surprisingly little is known about how people plan and control everyday physical actions, such as walking along and picking up objects. In order to explore this topic, we conducted an experiment in which university students were asked to pick up a common object (a child's beach bucket) that stood on a table several meters from the participant's start position. The bucket stood either on the left side, in the middle, or on the right side of the table and, depending on instructions, was to be carried to a farther target whose horizontal position was also varied. The questions were which side of the table the participant would walk along when picking up the bucket and which hand the participant would use to pick up and carry the bucket. Participants, most of whom were right-handed, preferred to walk along the left side of the table and to pick up the bucket with the right hand, although they departed from that preference when the reaching distance across the table was uncomfortable or if the target was too far to the right. The data were well fit with a mathematical model that included a right-hand bias and an estimate of functional distance that expressed the cost of reaching over some distance as approximately twice the cost of walking over the same distance.