Purpose: Comprehension of syntactic language is facilitated by the executive function of Prefrontal Synthesis (PFS), defined as an ability to deliberately modify and juxtapose mental visuospatial objects. Autistic individuals often experience deficits in PFS. This study aimed to differentiate between two hypotheses regarding PFS acquisition. The first suggests a persistent, age-independent barrier that continuously hinders PFS development. The second proposes an age-dependent factor, such as a critical period for PFS acquisition. These hypotheses predict distinct learning trajectories: the first expects autistic individuals to exhibit a consistently slower PFS-learning rate across all ages, while the second predicts an initial learning rate comparable to neurotypical peers, followed by an early decline.
Methods: To test these predictions, we analyzed PFS development in 15,183 autistic and 138 neurotypical individuals aged 2 to 22 years using parent-reports.
Results: At age 2, both groups exhibited similar PFS-learning rates. In neurotypical individuals, this rate remained high until age 7. However, in autistic individuals, learning rates began to decline exponentially as early as 2.3 years, with an even earlier onset in those with severe autism.
Conclusion: These findings support the second hypothesis, suggesting that PFS deficits in autism may stem from an age-dependent factor, such as a shortened critical period.
Keywords: Critical period, sensitive period, first language acquisition; Grammatical language; Language acquisition; Recursive language; Syntactic language.
© 2025. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.