Kids’ brain myths, checked against the science

Ten things parents hear all the time, and what the research actually says.

• Does sugar make kids hyper?No. A 1995 JAMA review of 23 blinded experiments found no effect of sugar on behavior, and a 1994 study found parents’ beliefs did the work.
• Do we only use 10 percent of our brain?No. Brain imaging shows activity all over the brain, and the 10 percent claim has no research behind it. Where it came from and what matters for kids.
• Is my child left-brained or right-brained?Neither. A 2013 study of 1,011 brain scans found no left-brained or right-brained people. What’s true about the two halves, and how to drop the labels.
• Are visual, auditory and kinesthetic learners real?Kids have preferences, but teaching to a “style” hasn’t been shown to help. A major review found almost no good evidence. What to do instead.
• Is the brain fully developed at 25?No finish line exists. The brain keeps maturing into the twenties, and the prefrontal cortex settles late. What “under construction” means for teens.
• Does a dopamine detox work for kids?A “dopamine detox” isn’t a real thing, and dopamine isn’t a toxin. What the idea gets half right, and the small habit changes that actually help kids.
• Is dopamine the pleasure chemical?Mostly no. Research by Berridge and Robinson links dopamine to wanting and learning what pays off, more than to enjoyment. Why that matters for kids.
• Is cortisol bad for kids?No. Cortisol wakes the body up and rings the alarm in real danger. The problem is stress that never stops and kids facing it without a supportive adult.
• Does testosterone cause aggression in teen boys?Barely. A 2020 meta-analysis found a very weak link between testosterone and aggression. What drives teen anger is sleep, stress and a growing brain.Teens 13–17
• Does the AAP still say 1 hour of screen time?Not as a fixed rule. The AAP’s January 2026 policy swapped the 2016 one-hour advice for family media plans, the 5 Cs and loose example ranges.

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