Course:KIN366/ConceptLibrary/Reaching and Grasping

Movement Experiences for Children
KIN 366
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Instructor:	Dr. Shannon S.D. Bredin
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Definition

Reaching and Grasping, also known as prehension, is a rudimentary motor skill common to all developing infants. This skill is not only essential for the infant's survival, but also critical for his or her development of fundamental motor skills, particularly manipulative skills such as throwing and catching. Over sixty years' worth of research has been done on reaching and grasping, exploring its movement patterns, internal and external influences, and ways to promote its acquisition in both typically and atypically developing infants. The skill of reaching and grasping can be defined as "[to] stretch out an arm in a specified direction in order to touch or grasp (to seize and hold) something." Prehension allows infants to interact with and explore the environment by manipulating the objects, developing both motor and cognitive functions. Although infants are born with a palmar grasp reflex, true voluntary grasping generally starts developing simultaneously with voluntary, directed reaching, at around four to five months of age Prehension can be classified into two phases: Phase I and Phase II, where these phases are not fixed, but are broad guidelines to follow development and progression of the skill acquisition.

Phase I

Phase I is generally characterized by:

• "One-handed reaching"
• "Child reaches when they see an object"
• "Once the child makes manual contact with the object, vision facilitates hand closure (grasp)"

Phase II

Phase II is generally characterized by:

• "The child attempts different types of grasps (depending on the object size and texture)"
• "Infant uses two hands"
• "Infants use vision to correct their reach"
• "Unlike Phase I, hand closure becomes tactile stimulated rather than vision guided"

Typical Timeline

• "4 months - prehension is controlled by the shoulders and arms; incapable of making contact with the object"
• "5 months - prehension is controlled by wrist, hand, and finger control; plus thumb in opposition to the fingers; crude contact with object"
• "6 months - a primitive squeeze grasp emerges (fingers close around the object"
• "9 months - prehension can be controlled by thumb and one finger (pincer-grip); fingertips of the 3 fingers oppose the action of the thumb in the grasp"
• "13 months - fore fingers grasp"
• "18 months - the child can finally release the object"

Biomechanics

In general, the reaching action consists of two parts, an initial arm extension toward the object and a final correcting and grasping of the object. In an experiment by Fagard et al.,(2009) the experimenter had infants reach for objects either on their left side or the right side. They found that younger infants initially have an ipsilateral approach toward the object, but they grasp the object with the contralateral hand, which allows more time for planning and reaching for the object. Older infants, however, generally demonstrate both ipsilateral approach and grasp. Another difference is that, as infants become more skilled, the reaches become straighter and the time spent decelerating the movement becomes shorter. This is mainly due to the increasing visual feedback used to guide the hand toward the object. The size and regidity, or texture, of the object also influences the infant's use of different grasping techniques. Infants will prefer smaller toys with soft texture because they are able to manipulate them more easily, with one hand. For larger objects, infants will use both hands to reach and grasp the object, although unimanual reaches occurs more frequently if the object is soft.

Toward the end of the first year of life, the movements become more refined and smooth, prehension attempts increases, movement velocity is faster, and there is a decrease in the number of trajectory corrections. It has been suggested that learning how to adjust movements contributes as a foundation for new skills such as face preferences, object segregation, and language.

Preparation for Reaching and Grasping

Infant movements occur as early as 8 weeks of age, and we see hand-mouth movements when the fetus is around 10 weeks old. What was once a simple reflex gruadually develops into an infant's directed movements to the mouth. In an experiment by Lew and Butterworth (1997), when infants are holding an object at two to three months of age, the amount of hand-mouth contacts are equivalent to rates when the infant is not holding anything. However, by four months, hand-mouth contacts increases significantly, indicating some neurophysiological changes. Together with these movements, the mouth also opens more frequently to explore the object at hand. Two affordances are essential for the acquisition and development of prehension: visual input and postural control.

Vision

Visual input and interpretation is one of the first processes that humans develop and integrate into the daily, practical life. Vision is a main affordance that guides and controls grasping both in infants and adults. McCarty and Ashmead (1999) carried out an experiment to explore the influence of vision and memory on reaching and grasping tasks. They had both adults and infants of 5,7 and 9 months perform the same task of reaching for an illuminated object which sometimes darkened during the reach. It was found that infants take a longer time reaching for the object while it was illuminated, since there were more corrections made via the visual information. This is an example of the speed-accuracy trade-off. It is also noteworthy that the infants contacted and grasped objects that darkened, showing that they didn't necessarily have to visually monitor their performance while reaching for the object. An infant's increasing ability to control his or her arm movements and interpret visual information may decrease the need to see an object throughout the reach.

In a follow-up study, McCarty et al. (2001) had infants reach for rods under three different lighting conditions: (1) sight of the hand was removed, (2) sight of the object was removed near the end of the reach, and (3) sight of the object was removed prior to reach onset. They also varied the orientation (vertical vs. horizontal) to see if grasping orientation changed as well. At seven and nine months, infants successfully oriented their hands to the rods in all three scenarios. The experiment shows that sight of the hand is not important once they develop the motor control for preorientation of their hand. Vision aids in the development of proprioception, but once they have adequate proprioceptive control of their arms and hands, vision is not needed. At that age, infants can initiate and complete a reach without visual support.

Posture

Posture, from head control to the ability to sit and stand, affects an infant's ability to reach and grasp objects. This is because prehension is directly related to an infant's need to maintain a stable vision of the target, that is, not perturbing the head and torso while moving the arms. It is important to remember that neonates are born with a disproportionately large head, causing it to wobble, thus head control is crucial. Infants are born with the asymmetric tonic neck reflex, which can be elicited up to 4 months, and it facilitates body awareness and development of hand-eye coordination. For example, when the infants are able to sit, they free their hands to manipulate objects. Studies show that during the early stages of reaching, the muscle activity mainly comes from the elbow flexors and extensors. However, as the child gains strength and control of their wobbly head, the muscle activity shifts to stronger shoulder and neck muscle activation, as opposed to the biceps and triceps.

How it develops

Dynamic Approach

Wimmers and his colleagues (1998) proposed that the development of reaching and grasping occurs in qualitative steps, that it is discontinuous and there is a phase transition, from a state of reaching without grasping to a state of reaching with grasping. They found that within a margin of 1 to 2 weeks, percent of reaching with grasping increased from 0 - 20% to 50 - 80%. Interestingly, after the jump, they found both phases present, although reaching with grasping dominated most of the action. This shows that the phase transition happened before the previous phase ceased to occur. Another thing Wimmers et al. noticed was that passage time (time between presentation of stimulus to onset of reaching) decreased as the at the same time the reaching and grasping spurt occurred. They state that an "increase in the stability (or 'attractiveness') of a behavioral category or activity is required [...] before new [...] behavioral modes can emerge within that behavioral category."

Foroud and Whishaw (2012) agree with Wimmers et al., and performed a longitudinal study to explore the ontogeny of the integration of the hand, upper-limbs, and whole body posture support. Instead of two phases, they present five main movement patterns that are present as infants learn to reach and grasp, progressing from head and mouth, to whole-body, to hand-centered. Those are:

• A. Diffuse prereaching
• B. Head- and mouth-directed prereaching
• C. Whole-body-directed prereaching
• D. Arm- and body-directed reaching, and
• E. Hand-directed reaching

There is a progressive transition from serial (A and B) to simultaneous (C and D) to sequential (D + E) levels of movement organization. Characteristic of infant reaching is that they reach bilaterally, or with both hands. This is because one arm reaching requires "controlled lateral movements of the torso coupled with inhibitory movements of the torso, legs, head and opposing arm." This supports the cephalo-caudal and proximal-distal progress of development, since we see hand-directed reaching happening only after the infant has control of activation and inhibition of his or her core muscles. This is a dynamic systems approach because various aspects need to be in place, such as vision, head and body control, strength in muscles, etc, before the infant can successfully reach and grasp something unilaterally. The slowest step to develop, which varies from infant to infant, is the rate-determining step.

Atypically Developing Infants

Although studies on reaching and grasping are extensive, only general conclusions or characteristics can be found regarding atypically developing infants. This is mainly because the sample tends to be small and heterogeneous. Along with that, most studies on atypical children are with high- and low-risk preterm children as well as exposure to cocaine, whereas conditions like cerebral palsy, and Down's syndrome are less studied.

Hadders points out that in low-risk preterm infants, there are actually more movements of reaching and grasping during the first 6 months of birth, however, during the second half, the infants have less efficient reaching movements. For high-risk preterm infants, the development of reaching and grasping is generally delayed and prehension is not kinematically and biomechanically efficient. Data also shows that the achievement of postural milestones is also delayed, such as sitting independently and neck and trunk control. As mentioned above, these are essential to free the infants' hands to reach and grasp objects.

Down's Syndrome

In a study involving children with Down's syndrome (DS), infants were observed to start prehension at around 4-5 months, the same age as typically developing infants start reaching. These infants participated in an early intervention program since 2 months of age, which could explain this finding, as opposed to the common thought that children with DS would have a delayed onset of motor activities. More pronounced differences started to emerge at 5 to 6 months, where the straightness of reach and trajectories differed from typically developing infants. The reach was generally performed with extreme postures, which may be a consequence of typical intrinsic factors related to people with DS such as hypotonia, ligamentous laxity and sensory deficits. Along with this, more movement units, or attempts-of-correction, were seen due to the lack of movement control. Some other results that were found from Campos and her team's study (2009) was that no differences were found in mean velocity of reach and deceleration time between typically developing infants and infants with DS. Although grasping improved with age in both categories, typically developing infants had substantially larger improvements when compared to the DS group.

For more on children with Down's Syndrome, Downs Syndrome Education Online provides more in depth research concerning motor development on children with DS, beyond the motor skill of reaching and grasping.

Recommendations

Prehension is critical for childhood development principally because it is fundamental for the development of a whole set of motor skills. These include writing with pens, throwing and catching balls, using knives and forks, dressing, and so forth. Along with these motor skills, there is also an increase in muscular strength and agility, as well as neurological development due to the interaction with the environment. This is why it is important to provide your children with opportunities to practice and perfect reaching and grasping with both hands.

The Texas School for the Blind and Visually Impaired gives few advices on the acquisition and development of reaching and grasping here. A few of the suggestions include:

• "Give your child lots of opportunities for weight bearing on his/her hands"
• "Place various objects in his/her hands [...] Use a variety of textures, sizes, shapes and weights."
• "Encourage your baby to bring his/her hands together and grasp his/her own hands. Gently stroke his/her hands, rub or pat them together, or pat his/her hand on yours."
• "Use tactile exploration activities where two hands can work together [e.g. finger paint, sand ...]"
• "Try two-handed activities, where one hand holds, the other hand manipulates"
• "Try two-handed activities, where both hands move actively"

Hadders provides three guidelines for atypically developing children:

• "Practice of balance control during daily activities"
• "Provision of situations in which the infant may easily experience the joy of reaching and grasping a toy"
• "Challenge of infant reaching in sitting situations that require substantial active postural control"

References

• Campos, A. C., Rocha, N. A., & Savelsbergh, G. J. (2009). Reaching and grasping movements in infants at risk: A review. Research in Developmental Disabilities, 30(5), 819-826.
• de Campos, A. C., Rocha, N. A., & Savelsbergh, G. J. (2009). Development Of Reaching And Grasping Skills In Infants With Down Syndrome. Research in Developmental Disabilities, 31, 70-80.
• Definition of grasp in English:. (n.d.). Grasp: definition of grasp in Oxford dictionary. Retrieved February 21, 2014, from http://www.oxforddictionaries.com/definition/english/grasp?q=grasp
• Definition of reach in English:. (n.d.). Reach: definition of reach in Oxford dictionary. Retrieved February 21, 2014, from http://www.oxforddictionaries.com/definition/english/reach?q=reaching
• Fagard, J., Spelke, E., & Hofsten, C. v. (2009). Reaching and grasping a moving object in 6-, 8-, and 10-month-old infants: Laterality and performance. Infant Behavior & Development, 32, 137 - 146.
• Fine Motor Development. (n.d.). Fine Motor Development. Retrieved February 24, 2014, from http://www.tsbvi.edu/seehear/spring99/finemotor.htm
• Foroud, A., & Whishaw, I. Q. (2012). The consummatory origins of visually guided reaching in human infants: A dynamic integration of whole-body and upper-limb movements. Behavioural Brain Research, 231(2), 343-355.
• Hadders-Algra, M. (2013). Typical and atypical development of reaching and postural control in infancy. Developmental Medicine & Child Neurology, 55, 5-8.
• Hofsten, C. V., & Rönnqvist, L. (1988). Preparation for grasping an object: A developmental study.. Journal of Experimental Psychology: Human Perception and Performance, 14(4), 610-621.
• Voluntary Movement of Infancy. (n.d.). Voluntary Movement of Infancy. Retrieved February 21, 2014, from http://www.d.umn.edu/~dmillsla/courses/motorlearning/documents/vountarymovementofinfancy.pdf
• Lew, A. R., & Butterworth, G. (1997). The development of hand-mouth coordination in 2- to 5-month-old infants: Similarities with reaching and grasping. Infant Behavior and Development, 20(1), 59-69.
• Rocha, N. A., Campos, A. C., Silva, F. P., & Tudella, E. (2013). Adaptive actions of young infants in the task of reaching for objects. Developmental Psychobiology, 55(3), 275-282.
• McCarty, M. E., & Ashmead, D. H. (1999). Visual Control of Reaching and Grasping in Infants. Developmental Psychology, 35(3), 620-631.
• McCarty, M. E., Clifton, R. K., Ashmead, D. H., Lee, P., & Goubet, N. (2001). How Infants Use Vision for Grasping Objects. Child Development, 72(4), 973-987
• Sacks, B., & Buckley, S. (n.d.). Motor development for individuals with Down syndrome – An overview. Motor development for individuals with Down syndrome – An overview. Retrieved March 1, 2014, from http://archive.down-syndrome.org/information/motor/overview/?page=3
• Thelen, E., & Spencer, J. P. (1998). Postural Control During Reaching in Young Infants: A Dynamic Systems Approach. Neuroscience & Biobehavioral Reviews, 22(4), 507-514.
• Wimmers, R. H., Savelsbergh, G. J., Beek, P. J., & Hopkins, B. (1998). Evidence for a phase transition in the early development of prehension. Developmental Psychobiology, 32(3), 235-248.