Coming to grips with weight perception: Effects of grasp configuration on perceived heaviness

We investigated how changes in grasp configuration affect perceived heavine ss in a weight discrimination task in which participants compared the weigh ts of a series of test objects with the weight of a reference object. In di fferent experiments, we varied the width of the grasp, the number of digits employed, the angle of the grasp surface, and the size of the contact area between the digits and the object. We show that objects are perceived to b e Lighter when lifting with (1) a wide grip in comparison with a narrow gri p, (2) five digits in comparison with two digits, and (3) a large contact a rea in comparison with a small contact area. However, the angle of the cont act surfaces did not influence perceived weight. We suggest that changes in central motor commands associated with grasp differences may influence per ceived weight, at least under some conditions.