Object familiarity affects finger shaping during grasping of fruit stalks

In experiment 1 participants reached and grasped equal green stalks of a green apple and a red strawberry. Stability of the two fruits was equalised by fixing the fruits on the table plane where they were reached for and grasped. The results confirmed that finger shaping was influenced by the size of the fruit body (Gentilucci 2002). Finger shaping was larger when grasping the apple stalk than the strawberry stalk. In addition, deceleration phase lengthened when reaching to grasp the strawberry stalk. In experiment 2 participants reached for and grasped equal wooden matches substituting the stalks of the same apple and strawberry presented in experiment 1. No effect of the fruit body was observed on grasping and reaching the matches. This result excluded that the closeness of the stalk to the fruit body was responsible for the interference effect observed in experiment 1. In experiment 3 participants reached for and grasped equal green stalks of an apple and a strawberry of the same red colour. The same results as in experiment 1 were found. They excluded that a grouping effect due to the same green colour of the stalk and the apple body was responsible for the interference effect observed in experiment 1. Results are discussed as further support of the hypothesis that an object is globally analysed when interacting with it, and familiarity, i.e. the way by which a familiar object is commonly grasped, strongly influences all the other possible interactions with it.