Individual Differences Research www.idr-journal.com 2011, Vol. 9, No. 2 , pp. 73-83 ISSN: 1541-745X © 2011 Individual Differences Association, Inc. 73 Personality Trait Differences between Typically Developing Children and those Diagnosed with Autism Spectrum Disorder Carrie L. Fortenberry, Cathy L. Grist, & David M. McCord* Western Carolina University *David M. McCord; Department of Psychology, Western Carolina University; Cullowhee, NC 28723; mccord@wcu.edu (e-mail). ABSTRACT - Early identification of autism is strongly associated with more positive outcomes. Many assessment instruments have been developed for this purpose, most of which focus on specific symptoms of autism. More recently, this effort has expanded to include assessment instruments based on temperament and personality. The present study used the M5-PS-45 Questionnaire, based on the five-factor model of personality, to compare personality trait differences in children with autism (n = 8) and typically developing children (n = 7) ages 3 to 5. Typically developing children received significantly higher scores on Extraversion, Conscientiousness, and Openness to Experience. The groups did not differ on Agreeableness or Neuroticism. These results are discussed in terms of implications for early identification of autism spectrum disorders. The occurrence of autism spectrum disorder (ASD) has increased notably within recent years (Centers for Disease Control and Prevention, 2009). When Kanner first described autism in 1943, it was considered a rare disorder affecting 2 to 4 out of every 10,000 children. Most recent statistics as indicated by the Autism and Developmental Disabilities Monitoring Network show that 1 in 110 children are diagnosed on the autism spectrum (Centers for Disease Control and Prevention, 2009). Furthermore, children are being diagnosed with autism at an earlier age (Baron-Cohen, Allen, & Gillberg, 1992; King & Bearman, 2009; Liu, King, & Bearman, 2010). Children were most commonly diagnosed at 37 months of age in 2005, compared to between 53 and 66 months in 2002, (Centers for Disease Control and Prevention, 2009; Mandell, Novak, & Zubritsky, 2005). A number of factors contribute to the increased prevalence and earlier diagnosis of autism, including broadened diagnostic criteria (Centers for Disease Control and Prevention, 2009) and increased awareness among parents and teachers (Wing & Potter, 2009). While these explanations may account for some of the increase, a true rise in incidence is also suggested (Waterhouse, 2008; Wing & Potter, 2002). At present, the causes of autism are not fully understood. Twin studies strongly suggest a genetic component (e.g., Bailey et al., 1995). Shelton, Tancredi, and Hertz- Picciotto (2010) found a link between maternal age and incidence of the disorder; thus, one contributor to the steady rise in prevalence may be delayed childbearing in women. Rogers, Savery, and Shattock (1999) found that diet impacts behavioral symptoms in