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Frame-by-Frame Video Analysis of Idiosyncratic Reach-to-Grasp Movements in Humans
Published on: January 15, 2018
Can size and rigidity of objects influence infant's proximal and distal adjustments of reaching?
Fernanda P S Silva1, Nelci A C F Rocha, Eloísa Tudella
1Departamento de Fisioterapia, Universidade Federal de São Carlos, São Carlos, SP, Brasil. silva.fernandapereira@gmail.com
Insights
Infant reaching skills refine significantly from 6 to 36 months. Infants adjust hand movements and grasping based on object size and malleability, demonstrating developing motor control.
Area of Science:
- Developmental psychology
- Motor control
- Infant reaching behavior
Background:
- Object properties influence reaching in young infants.
- Limited research exists on how these adjustments change in older infants.
Purpose of the Study:
- To investigate the influence of object size and rigidity on reaching adjustments in infants aged 6, 7, 8, and 36 months.
- To analyze both proximal and distal reaching adjustments.
Main Methods:
- Nine healthy infants participated.
- Infants interacted with objects varying in size (large/small) and rigidity (rigid/malleable).
- Reaching movements were videotaped and analyzed for proximal (unimanual/bimanual) and distal (hand orientation, hand shape) adjustments, and grasping success.
Main Results:
- 36-month-olds used more unimanual reaching, especially for small objects.
- Hand orientation evolved from oblique/vertical (6-7 months) to horizontal (36 months) for touching and grasping.
- Hands opened more over time, particularly for large rigid objects, and grasping success increased for malleable/small objects.
Conclusions:
- Reaching becomes more refined between 6 and 36 months.
- Infants demonstrate adaptive adjustments to object properties (size, rigidity) in their reaching and grasping.
- Changes in proximal and distal adjustments reflect developmental refinement of motor skills.
Background:
It has been found that objects influence the adjustments to reaching of breastfeeding infants, however, it has not been investigated whether these adjustments change in older infants.
Objectives:
The aim of this study was to determine whether the size and rigidity of objects influence the proximal and distal adjustments to reaching of infants of 6, 7, 8 and 36 months of age.
Methods:
Nine healthy infants were presented with: one large rigid, one small rigid, one large malleable and one small malleable object. The movements were videotaped and later analyzed qualitatively with regard to proximal (unimanual and bimanual reaching) and distal adjustments (horizontal, vertical and oblique hand orientation, opened, half-open and closed hand) and with regard to grasping of these objects (with and without). Friedman test and Dunn multiple comparisons were applied and 0.05 was considered as a significant difference.
Results:
Infants of 36 months of age performed more unimanual reaching than younger infants. Additionally, at all ages, unimanual reaching was particularly performed for small objects. At 36 months of age infants guided the hand horizontally to touch and grasp the objects, while at 6 and 7 months the hand orientation was oblique to touch and vertical to grasp the objects, regardless of the object's properties. Over the months, both at the beginning and at the end of reaching, the hands became more open, especially to touch the large rigid object, and infants increasingly performed reaching with successful grasping, especially for malleable or small objects.
Conclusions:
From 6 to 36 months of age, the reaching became more refined and the infants adjusted to the different properties of the objects which were observed through changes in the proximal and distal adjustments.
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