Movement strategies in a haptic search task

Movement strategies were investigated in a haptic search task where participants indicated whether a target was present among a varying number of items. Hand movements were classified according to two criteria into three movement types. Results indicated that an easy search was performed with a parallel strategy, while in a more difficult search a serial movement strategy is used. Short, fluent movements were made in the easy search, whereas the difficult search showed more detailed movements and this amount increased when more items were to be searched. These differences between the search tasks remained when corrected for travelled distance, while path length could partly explain dissimilarities between trials with a target present and absent. Overall, these results indicate that movement strategies are adjusted primarily to the search condition and the salience of the target, and less to the presence of a target and set size.