Question

By 8 to 9 months of age the infant grasps a larger object between the thumb and the radial fingers and readily varies the grasping pattern according to the shape of the object. However, intrinsic muscle control is not yet effective because the infant does not use grasp with ____ flexion and ___ extension.

Answer 1

Infants between 8 and 9 months old grasp objects between their thumb and radial fingers. They can vary their grasping pattern based on the object's shape. However, their intrinsic muscle control is not yet effective because they don't use grasp with MCP flexion and IP extension.

Answer 2

Infants at 8 to 9 months old can grasp larger objects with thumb and radial finger coordination but lack full intrinsic muscle control for opposed thumb flexion and finger extension, which are necessary for more precise dexterity.

Step-by-step explanation:

By 8 to 9 months of age, the infant grasps a larger object between the thumb and the radial fingers and readily varies the grasping pattern according to the shape of the object. However, intrinsic muscle control is not yet effective because the infant does not use grasp with opposed thumb flexion and finger extension.

The opposition movement of the thumb toward the fingers of the same hand is crucial for the ability to grasp and hold objects. At this age, infants are developing the coordination and fine motor control of their fingers and thumbs, but are not yet fully adept at using all the intrinsic muscles of the hand, which include actions such as flexing, extending, abducting, and adducting the more distal finger and thumb segments.

Motor development follows a sequence where infants progress from reflexive actions to more advanced motor skills like the pincer grasp - using the tips of the thumb and forefinger - which is usually acquired around ten months of age.