Along with spoken language, being dominant in the left or right hand -- also known as handedness -- is one of two distinguishing characteristics of humans when compared with other animals, according to Science Daily. Your child typically will establish his dominant hand by age three; however, signs that appear as early as in the womb can give clues to the hand with which your child will write, according to Dr. Jeffrey Hull, a pediatrician writing on DrHull.com.
Examine ultrasound photos of your child. If your child has one foot rotated and pointing out more than the other, this could indicate the dominant side, according to Dr. Hull. Because most Americans are right-handed, for most children this will be the right foot pointing outward.
Observe your child as an infant for signs of raising one arm, clenching a fist or turning her head more to one side than another. These can be early signals as to with which hand your child will write.
Watch your 6- to 9-month-old child reach for a toy or other object. At this age, your child may show a preference for a particular hand. This is true regardless of the side you place the toy. Although your child will likely use both sides, you may find one side is slightly more dominant.
Observe your child playing with his toys when he reaches 12- to 18-month of age. At this time, your child may reach for a toy with his non-dominant hand and then manipulate the toy with his dominant hand. This is because the actual manipulation of a toy takes more work and control than holding the toy.
Watch your 18-month old child as she plays. At this time, her dominant hand should be emerging because, at this age, she is using more complex hand motions. Your child will likely use her preferred hand when at play, when eating and when performing most other activities.