Haptic intramodal comparison of texture in human neonates

We investigated neonates' capacity to haptically compare objects varying in texture property. Right-hand manual activity, assessed by holding time and hand-pressure frequency, was recorded for objects in the presence (test period) or absence (pretest and post-test periods) of an object simultaneously held in the left hand. Thirty-two babies were assigned to four experimental conditions according to the texture density of the object held in each hand: Objects had either the same (matching conditions) or different (non-matching conditions) texture density. Although holding time decreased during test period in both conditions, hand-pressure frequency changed according to the matching and non-matching conditions. In the matching condition, hand-pressure frequency of the right hand did not differ from hand-pressure frequency of the left hand. In the non-matching condition, hand-pressure frequency recorded from the right hand was significantly higher than hand-pressure frequency recorded from the left hand. These results point to neonates' capacity to compare information between simultaneously held objects. These results are interpreted in relation to existing data on the early capacity for intermodal exploration of objects.