An Eye Tracking Study of Rapid Automatized Naming Ability in Adult Siblings of Individuals with ASD

Background:  Rapid automatized naming (RAN) ability is strongly associated with reading ability, and it is theorized that phonological processing deficits contribute to impairments in RAN (Wolf et al., 2000). Given that impaired phonological processing, reading delays, and various language-related deficits have been reported in individuals with ASD and their first-degree relatives (Bolton et al., 1994; Hughes et al., 1999), it follows that examining RAN might help to clarify the role that phonological processing plays in the language-related phenotypes of ASD. Interestingly, RAN abilities do appear to be impaired in individuals with ASD and their parents (Losh et al., 2010; Piven & Palmer, 1997), though no studies to date have examined the ability in adult siblings. Furthermore, the underlying processes that contribute to RAN performance in first-degree relatives of individuals with ASD remain unknown. Eye tracking technology has been used extensively to investigate the link between eye movements and spoken language during picture naming and sentence production in typical adults (e.g., Griffin & Bock, 2000; Meyer et al., 1998), and during the RAN task in individuals with dyslexia (Jones et al., 2006). These studies have shown that the time spent looking at objects during naming reflects the amount of time required for phonological retrieval. As such, this preliminary study utilizes eye tracking to determine if longer looking time is related to impaired RAN performance in adult siblings of individuals with ASD (ASD-Sibs). 

Objectives:  To compare RAN ability in adult ASD-Sibs to adult controls, and to investigate the relationship between eye movement patterns and performance on RAN.

Methods:  Seven ASD-Sibs (57.1% male; mean age = 20.79 years) and seven control subjects (42.9% male; mean age = 21.45 years) participated in this study. Speed and number of errors were measured during a RAN task consisting of color, letter, digit, and object naming. Total amount of time spent looking at items during naming was measured using a Tobii X60 eye tracking device. 

Results:  ASD-sibs demonstrated slower naming than controls on Letter and Digit trials (ts >  2.60, ps < .05). Likewise, ASD-Sibs spent more time looking at items than controls during Digit naming, t(11) = 2.55, p < .05), and group differences for looking time during Letter naming approached significance (p = .06). ASD-Sibs also committed more errors during Color naming, t(12) = 2.40, p < .05). For both groups, looking time was highly correlated with speed of naming (all rs > .90, ps < .001), but not number of errors.

Conclusions:  Results suggest that RAN abilities are impaired in adult siblings of individuals with ASD, relative to healthy adult controls, providing additional evidence that RAN is a promising marker of genetic liability to ASD. Results from eye tracking analyses indicate that ASD-Sibs are looking longer at items for trials on which they are slower at naming, which may be suggestive of slower phonological processing (Meyer, 1998). Future studies will expand this preliminary study to include additional subjects and fine-grained analyses of the temporal relationship between looking and speaking during rapid naming.