Cataloguing and Characterizing Interests in Typically Developing Toddlers and Toddlers Who Develop ASD

Background:   Little is known about the prospective emergence of restricted interests in autism spectrum disorder (ASD).

Objectives:   Our aims were three-fold: 1) attempt a replication and extension of DeLoache et al. (2007) findings that indicate a greater proportion of typically developing toddler/preschool-aged males show extremely intense interests as compared to similar aged females; 2) examine whether the intensity and/or peculiarity of interests reported at 18 or 24 months differentiated children at high-familial-risk who later met diagnostic criteria for ASD at 24 months as compared to high and low risk children who did not meet diagnostic criteria at 24 months; and 3) test a feature of the “extreme male brain theory” by examining whether females at high-familial risk for developing ASD show a greater proportion of male sex-typed interests as compared to low-risk females.

Methods:   The Intense Interests Inventory (Elison & Bodfish, 2009) was conducted in a semi-structured interview format.  Parents reported their child’s primary interests at 18 and 24 months of age in the context of the IBIS study.  Interests were rated by clinical examiners on a 5-point scale with respect to the intensity and peculiarity of each interest listed.  The sample consisted of 95 low-risk infants (53 males), 157 high-risk infants who did not meet diagnostic criteria for ASD at 24 months (86 males), and 38 high-risk infants who met diagnostic criteria for ASD at 24 months (33 males).

Results:   1) Among children not meeting diagnostic criteria for ASD at 24 months, a Mann-Whitney U test revealed that the distribution of intensity ratings varied across sex (p = 0.029) at 18 months of age, with a greater proportion of males showing moderate or intense interests as compared to females.  The effect of sex was not significant at 24 months. 2) Interests of high-risk infants who met diagnostic criteria for ASD at 24 months were rated as more peculiar at 18 months (Mann-Whitney U test, p = 0.006) and 24 months (Mann-Whitney U test, p = 0.030) as compared to those children not meeting diagnostic criteria.  The intensity of interests did not differentiate these two groups. 3) The proportion of females, who do not meet diagnostic criteria for ASD at 24 months and whose primary interest was classified as masculine, feminine, or indeterminate did not depend on familial risk status (18 months, p = 0.325; 24 months, p = 0.572).

Conclusions:   We report evidence partially consistent with DeLoache et al. (2007) that a greater proportion of males show intense interests at 18 months as compared to females, but this finding may be transient or specific to this age.  We also report evidence consistent with ADI-R conventions that peculiarity of interests and not the intensity of interests differentiate children who meet diagnostic criteria at 24 months of age.  Finally, our finding that females at high-risk for ASD do not show a greater proportion of male sex-typed interests as compared to low-risk females does not support the extreme male brain theory.