Gender Differences in Language Development Among Toddlers with Autism, Autism Features, Developmental Delay, and Language Delay

Background: Among typically developing children, females have more advanced language than males (Zambrana et al., 2012). Conversely, among children with autism, males may have an advantage over females (Lawson et al., 2018). Differences in language development may suggest gender differences in phenotypic presentations of autism, or that certain females (e.g. those with more advanced language skills) are being missed by current diagnostic practices. Examination of gender differences in language development among toddlers referred for developmental assessment may shed light on this matter.

Objectives: To examine whether language scores on the Mullen Scales of Early Learning (MSEL) differed between male and female toddlers with no delays, autism, autism features (i.e. toddlers with sub-clinical characteristics of autism), developmental delay, and language delay.

Methods: Data were collected as part of a larger study designed to screen, evaluate, and treat autism within the first two years of life. Analyses focused on a sample of toddlers (n = 302, mean age 20.77 months), matched on age and gender, diagnosed with autism (n males = 51, n females = 48), autism features (n males = 30, n females = 19), developmental delay (n males = 37, n females = 42), language delay (n males = 24, n females = 27) and no delays (n males = 9, n females = 15). Factorial MANOVA was used to determine the effect of gender and diagnosis (and their interaction) on MSEL receptive and expressive language scores.

Results: Depicted in Figures 1 and 2, a significant main effect of diagnosis on language development emerged, V = 0.34, F(8,582) = 14.88, p < .001. Bonferroni-corrected post hoc tests revealed that receptive language was significantly lower among toddlers with autism than those with autism features (p < .001), developmental delay (p < .05), language delay (p < .001), and no delays (p < .001). Expressive language was also significantly lower among toddlers with autism than those with autism features (p < .05), developmental delay (p < .05), language delay (p < .001), and no delays (p < .001). Both receptive and expressive language were significantly higher among toddlers with no delays than those with any delay (all ps < .001). Females had more advanced expressive language than males (p < .05), but the overall main effect of gender was not statistically significant (p = .09). Post hoc analyses restricted to toddlers with autism features revealed a significant gender difference (V = 0.16, F(2,46) = 4.32, p < .05), where females scored approximately 8 points (~ 0.8 SDs) higher than males.

Conclusions: Inconsistent with previous research, no significant gender differences emerged for language development among typically developing toddlers or toddlers with autism. Interestingly, females with autism features had the highest scores when compared to toddlers with any delay. This observed female advantage may be related to later diagnosis among females with autism who present without delayed language in toddlerhood (Goodwin et al., 2017). Future research should examine the developmental trajectory of toddlers demonstrating sub-clinical features of autism to improve early diagnostic practices.