ASL Proficiency Predicts Advanced Visual-Spatial Processing Independent of Age of Acquisition

We examined the cognitive effects of American Sign Language (ASL) proficiency in visual-spatial reasoning, challenging interpretations of the traditional critical period hypothesis that early language acquisition primarily predicts cognitive outcomes across domains. We analyzed behavioral tasks in 40 participants with varying levels of ASL fluency and age of acquisition (AoA) using cluster analysis. We assessed participants using the Vandenberg-Kuse Mental Rotation Test (VKMRT), a block design (BD) task, and the ASL Comprehension Test (ASLCT). Our results show that ASL proficiency, not early AoA, best predicts performance on visual-spatial tasks, suggesting that sustained engagement with ASL may be associated with enhanced visual-spatial reasoning. Regression analyses showed that ASLCT scores significantly predicted block design scaled score (b = 0.19, p < .05), while AoA did not contribute significant variance (∆R² = .007, p > .05). Complementary cluster analyses identified distinct cognitive profiles, confirming that high-performing subgroups were differentiated by proficiency rather than early acquisition. These findings support embodied cognition and experience-dependent neuroplasticity accounts of language-cognition relationships, while remaining consistent with evidence that critical period effects may differentially constrain core language acquisition more than related cognitive domains. We discuss implications for culturally and linguistically appropriate cognitive assessment practices for deaf and hard-of-hearing populations and provide recommendations for future studies.