The Emergence of Effortful Control in Young Boys With Fragile X Syndrome.

Robinson et al. (2018) watched boys with Fragile X syndrome for two years. They tracked effortful control, the toddler skill of stopping, waiting, and shifting attention.

The team compared the boys to same-age peers without disabilities. They used lab games and parent checklists every six months.

The FXS boys made no gains in self-control. Their scores stayed flat while typical boys kept improving.

By age five the gap was wide. The FXS group still acted like younger toddlers even though they practiced the same games.

Padmanabhan et al. (2015) saw a similar freeze in older kids with autism. Yet their study looked at teens, not preschoolers. The flat line looks opposite, but the kids were different ages and diagnoses so both can be true.

Gillooly et al. (2025) found fine-motor skills predict shifting in two-year-olds with autism. Marissa’s FXS boys also lag in shifting, hinting that early motor play might support later control.

Hsieh et al. (2014) showed preschoolers with autism struggle to plan ahead. Together these papers map early executive potholes across fragile X and autism before age five.

Do not wait for self-control to “mature” in FXS. Start stop-and-wait games, visual timers, and response-cost plans as soon as you see the child. Embed brief inhibition trials inside reinforcement-rich play and track data weekly so you catch tiny gains the normative charts will miss.