Apparent covariation between child habit disorders: effects of successful treatment for thumb sucking on untargeted chronic hair pulling.

Two kids who sucked their thumbs and pulled their hair got a bitter nail polish on their thumbs.

The team only told them the polish would stop thumb sucking. They never mentioned hair pulling.

They watched both habits for weeks to see if fixing one would change the other.

Both kids stopped thumb sucking within days.

Hair pulling also vanished even though nobody treated it.

The bitter taste on thumbs wiped out both habits at once.

Hayes et al. (1975) used a stronger punishment package for self-injury and got three-year suppression. This 1987 study shows a milder taste aversion can work when habits share the same response class.

Luiselli (1989) extended the idea to skin picking in a teen with gloves as the punisher. The pattern holds: treat one body-focused habit and similar ones may drop too.

Thakore et al. (2024) swapped taste for protective equipment with a child who mouthed his hands. Same outcome—one intervention cut the behavior—showing the principle survives across decades and populations.

Hastings et al. (2001) tested habit reversal for nail biting instead of taste. Both methods work, but taste gives you the bonus of wiping out untreated habits like hair pulling.

If a child has two body-focused habits, you might only need to treat the easier one. A simple bitter polish on thumbs could also stop hair pulling, skin picking, or nail biting without extra work. Check for untreated habits after you start any habit-reduction plan.