Hand Dominance, Crossing Midline and Brain Difference: What are they and how do they relate?

by Hope RISING Clinic’s therapy supervisor, Katherine Zintel, M.S., OTR/L

Imagine there’s a line running from your head to your feet, separating your left and right sides of the body – that’s your “midline”.  When you hear the term “crossing midline,” it means you are spontaneously crossing one side of your body over the other. For example, when coloring at the table I use my right hand to grab crayons that are on the left side of my body. We cross our midline numerous times throughout the day: writing, eating from a plate, gathering items in the pantry, or moving game pieces.

The ability to cross midline helps us develop a dominant hand. Hand dominance is an important developmental milestone that allows us to complete daily tasks quickly, accurately, and with minimal thinking power. Hand dominance is important in many activities, including: handwriting, using scissors, brushing our teeth and hair, cleaning up toys, and eating with utensils.

1. What strategies can help?

  • Screwing lids on and off jars: make it extra fun by having stickers or trinkets inside them
  • Coloring on small pieces of paper: this requires your child to hold the paper with one hand while coloring with the other.
  • Coloring or drawing on pieces of paper taped to a wall: drawing rainbows or infinity symbols that require the child to use the whole page.
  • Mixing and scooping: they can help mix cookie or pancake batter, or scoop dry beans and rice.
  • Home-made coin slots: cut a small hole in the lid of a plastic container and encourage your child to place small items in the hole, such as: pennies, dice, pompoms, toothpicks, paper balls, etc.
  • Playdough: pound the clay flat with one hand then play with cookie cutters to make fun shapes.
  • Legos, Duplos, and other building toys: requires one hand to hold while the other attaches or removes pieces.
  • Bats, racquets, and gold clubs: all these require both hands to work together and cross midline.

2. Words to use

  • Encourage your child to finish the project using the hand they started with.
  • If their hands get tired, encourage them to stop and rest rather than switching hands.
  • If they do switch during tasks, ask them which hand felt easier to use during the activity.
  • Use the terms “hero hand” and “helper hand” to help the child understand one hand is dominant. When cutting paper, the child would hold the scissors in their dominant “hero hand” and use their non-dominant “helper hand” to hold the sheet.

3. Is my child ambidextrous?

Although some people are truly ambidextrous, which means they can use both hands equally well, it is very uncommon. A person can be cross-dominant, which is having a preferred hand for different activities such as writing with their left hand and throwing a ball with their right hand. It is not typical for children to switch what hand they are using in the middle of an activity

4. Why does this happen/what age?

Starting as babies around six months, we begin reaching to alternate sides of our bodies to grab toys or play. This skill takes practice and wont become consistent and spontaneous until around three or four years old. Hand dominance can begin to emerge during toddler years and should become well established around six years old. Children who switch hands often during tasks may not yet have developed hand dominance.

5. How does this relate to brain difference?

When a child’s left and right sides of the brain don’t communicate well with each other, this can lead to difficulty crossing midline and therefore developing a hand dominance. Another reason children may not automatically cross midline is due to weak abdominal and back muscles.

Children who don’t automatically cross midline tend to be more clumsy, be resistant to playing sports, and can have poor fine motor skills including scissors and writing. Imagine if every time you practiced drawing you used a different hand; it would take twice as long to be good at it! With a hand dominance, a child is practicing with the same hand each time and developing the skills needed for academic success.

About the author: Katherine Zintel, M.S., OTR/L, is an occupational therapist and therapy supervisor at Hope RISING Clinic for Prenatal Substance Exposure. She is passionate about helping people reach their fullest potential and helping parents better understand their children. Katherine brings knowledge and skill to supporting children and families at the clinic from her experience as an in-home support specialist, residential treatment staff member, support staff in an alternative school, and therapy aide in a pediatric occupational therapy clinic. She grew up in a small town in Wisconsin and moved to the Pacific Northwest as a young adult. She finds enjoyment in having coffee on her front porch, hiking and backpacking, cooking with her husband, and laughing with her son.