USE OF ROD AS INSTRUMENT IN 3 YEARS OLD CHILDREN: AFFORDANCES AND EFFECTIVITIES

Abstract

We can accomplish the same goal using different combinations of our body segments. This phenomenon is termed ‘motor equivalence’ (Lashley, 1930). A tool is an object detachable from the environment, that coupled to our body extents our capacity of exploring and changing the environment (Beck, 1980; cf. St Amant, & Horton, 2008). The process of the use of a tool has neurological implications, affording the incorporation of the tool physical properties in our neuromotor system (Maravita, & Iriki, 2004; Catela, 2007; Ferreira & Catela, 2012). Even with only one trial, reaching to a target with a light weight rod we do similar trajectories those formed without the rod (Lacquaniti, Socchting, & Terzuolo, 1982). With this paper, we intended to verify if kindergarten children would be able to perceive the affordance of rods with various lengths to reach and push a light ball into a target.

The sample was composed by 13 kindergarten children (6 girls), with 3 years old. Informed consent and assent was obtained. Their arm was measured (27,8±2,3cm). Seven light rods with length differences between them of 7,5cm, starting at 22,5cm, till 67,5cm, were used; and the length of the intermediate rod (45cm) was summed to the individual arm length of the child, which was used to place him/her in front of a table with a light ball near him/her. Behind the ball there was a vertical target. So, the ball was in the extrapersonal space, i.e., the space outside the hand-reaching distance (Berti & Frassinetti, 2000); becoming in the personal space if the rod was provided, from the intermediate one till the longer one.

Showing to the child one rod at a time (the child didn’t touch the rod, only saw it in the hand of the experimenter), in an increasing or in a decreasing order of lengths, whose sequences where alternated among children, it was asked to him/her, for each rod, if he/she could push the ball to the target with that rod. After this condition, and for the rods where the child said that he/she could do it, the child had the opportunity to try to do it, and his/her actions were qualitatively analyzed.

The Mann-Whitney test was used for intergroup comparisons and Cochran test (Q), followed by McNemar test (with Bonferroni correction), were used for intragroup comparisons, and, the Contingency coefficient was used for association between variables; for a level of significance of ,05; through the IBM-SPSS program, version 24. No significant differences were found between genders and rods’ order of presentation.

The results revealed that with the shortest rod (25,5cm) 46,15% of the children responded that they could, and with the following one (30cm), 53,85% also said it. For the rod with the length of 37,5cm, the affirmative answer rose to 76,92%; and for the intermediate rod stood at 69,23%. For the longer rods, values were 100% and 92,31%. Overall, there was a significant difference of positive answers between rods (Q (13,6) = 21,447, p˂,002); however, no significant differences were found when paired comparisons were made. Because only with the intermediate rod a child would reach the ball, needing to totally stretch the arm, it meant that in the case of the shorter rods only if the child applied additional motor solutions he/she would reach the ball with the rod. In fact, for the shortest rod 66,7% of them extended the arm and rotated their shoulders, and 33,7% extended the arm and tilted the trunk. Arm extension with trunk forward tilt was a frequent motor solution, applied in the next rods (30cm- 57,1%; 37,5cm and 45cm- 40%; 52,5cm- 61,5%), falling to 18,2% in the 60cm rod length, and 7,7% with the 67,5cm one. For the last two rods, the most frequent solution was elbow extension, with 72,7% of occurrences with the 60cm rod and 76,9% with the 67,5cm one.

This study confirms that even before acting with the tool, the child has the capability to detect it affordances (cf. Gibson, 1979/1986), in order to use it in synergy with his/her own body’ degrees of freedom (articulations of the elbow, of the trunk and of the hip). The children also revealed the capacity to incorporate the length of the rods in their actions (cf. Bongers, Michaels, & Smitsman, 2004; Bongers, Smitsman, & Michaels, 2004), exchanging from use of more degrees of freedom to less ones, as the rods became longer. As the rods became longer, the motor solutions have evolved always to the most economical solution, because extending the arm is less tiring than tilting the trunk; and, no child used only the movement of the trunk to reach the ball with the rod. So, children also detected the interplay of the affordance of the rod with their effectivities (cf. van Leeuwen, Smitsman, & van Leeuwen, 1994), because with some capacity of differentiation, they changed postural solutions according to rod length (cf. Bongers, 2001). Additionally, motor equivalence was also present, because different children have presented different solutions for the same rod length. If children with 3 years old do have the perceptual capacity to detect tool affordances and to adapt to changes in the environment, it is essential to promote perceptual-motor stimulation at the kindergarten, in order to ensure an enriched child development (cf. Smitsman, & Bongers, 2003).