Mothers Exaggerate Their Finger Movements While Demonstrating Object Manipulation to Their Infants

Kaori Nagata,Goh Matsuda,Eriko Yamamoto,Kazuo Hiraki

doi:10.4236/psych.2018.912149

Abstract

We investigated whether mothers exaggerate the fine movements of their fingers when interacting with their infants, and whether infant-directed action is influenced by mothers’ beliefs about a demonstration-observer’s knowledge. Fifteen mothers demonstrated how to use a novel toy to their infant (Infant condition), an adult family member (Uninformed Adult condition), and an adult female who already knew how to use the toy (Informed Adult condition). An optical motion capture system was used to examine the mother’s wrist and finger movements, and her gaze was video recorded. Compared with the Uninformed Adult condition, in the Infant condition, mothers exaggerated their wrist movements when holding the toy in the same way as in previous studies, opened their fingers wider when reaching for the toy, and looked at the observer more often. There was no significant difference in hand movements between the Informed Adult and Uninformed Adult conditions: that is, the observer’s level of prior knowledge did not affect the mothers’ motions. This suggests that mothers may exaggerate their finger movements in order to attract their infants’ attention, not only while holding the object but even while initially reaching for it, while also monitoring the infant.

Highlights

IntroductionInfant-directed action began to be investigated by examining the kinematics of relatively large joints, such as their wrists and elbows using a three-dimensional (3D) motion tracking system (e.g., Fukuyama et al, 2015; Nagai, Nakatani, & Asada, 2010, Rohlfing et al, 2006)
When interacting with infants, mothers’ actions become exaggerated, slow, and more repetitive
In the reach-to-grasp phase, peak grip aperture was significantly larger in the Infant condition than in the Uninformed Adult condition (p < 0.05)

Summary

Introduction

Infant-directed action began to be investigated by examining the kinematics of relatively large joints, such as their wrists and elbows using a three-dimensional (3D) motion tracking system (e.g., Fukuyama et al, 2015; Nagai, Nakatani, & Asada, 2010, Rohlfing et al, 2006). This technique is insufficient to characterize infant-directed action fully, because most object manipulation in everyday life is carried out using movement of the fingers. It is necessary to examine the precise movements of the fingers during demonstrations of object manipulation

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Discussion

Conclusion