Notwithstanding the fact that the diagnosis of autism is becoming more standardized (Volkmar, Lord, Bailey, Schultz, & Klin, 2004), even today, a generally accepted definition is hard to find (e.g., Baird, Cass, & Slonims, 2005). However, all definitions identify impaired ability for social interaction and communication as well as idiosyncratic behaviors and deficits. Specifically, the term autism is used to describe a pervasive developmental disorder characterized by severe impairments in several areas of development including reciprocal social interaction skills, communication skills and the presence of restricted, repetitive, and stereotyped patterns of behavior, interests and activities (e.g., American Psychiatric Association, 2000; Damasio & Maurer, 1978; Happe & Frith, 1996; Mundy, Sigman, Ungerer, & Sherman, 1986; Sweeten, Posey, Shekhar, & McDougle, 2002).
In particular, the presence of deficits in the area of social interaction was the main reason that Kanner (1943) chose the term autism to describe a group of 11 children who demonstrated relatively common characteristics, different from those that appeared in the diagnosis of schizophrenia or childhood psychosis. Since then, social deficits have retained a prominent position in diagnostic systems (e.g., American Psychiatric Association, 2000;WorldHealth Organization, 1992) and many researchers have suggested that social impairments are the most critical element in the definition of this disorder (e.g., Anderson, Moore, Godfrey, & Fletcher-Flinn, 2004; Carter, Davis, Klin, & Volkmar, 2005; Constantino et al., 2003; Ruble, 2001; Scattone, 2007; Volkmar, Carter, Sparrow, & Cicchetti, 1993). Even during the first months of life, children with autism may not engage in simple social behaviours such as eye gaze, smiles, or responses to parents' efforts at verbalisation and play interaction (Hobson & Lee, 1998; Koegel & Koegel, 1999; Swettenham et al., 1998). Although, a variety of different treatment procedures have been designed, assessed, and evaluated to address these deficits a persistent problem remains; the establishment of more complex social behaviors. For example, it is a usual phenomenon that a child with autism may need continuous adult prompting to complete a sequence of already learned activities (MacDuff, Krantz, & McClannahan, 1993).
As long ago as 1981, Applied Behaviour Analysis (ABA) was identified as the treatment of choice for individuals with autism that offers the best outcomes. More than 19,000 papers have been published in peer-reviewed journals using ABA within a variety of areas, including well over 1100 studies concentrating on children with autistic spectrum disorders. This extensive research evidence has resulted in ABA being regarded as the best empirically evaluated intervention (e.g., Collaborative Work Group on Autistic Spectrum Disorders, 1997; Department of Health, 1999; MADSEC Autism Taskforce, 1999; Simpson, 2001; U.S. Department of Health and Human Services, 1999). Enough teaching methods based upon ABA have been conducted to suggest that not only is the approach effective, but as a congregate group of learning based methods, it stands alone as the only scientifically validated effective treatment(s) for individuals with autism (e.g., Cohen, Amerine-Dickens, & Smith, 2006; Eikeseth, Smith, Jahr, & Eldevik, 2002; Howard, Sparkman, Cohen, Green, & Stanislaw, 2005; Mudford, Martin, Eikeseth, & Bibby, 2001; Remington et al., 2007; Sallows & Graupner, 2005; Smith, Groen, & Wynn, 2000; Stahmer & Ingersoll, 2004). These teaching methods have incorporated basic behavioral principles such as positive reinforcement, prompting, shaping, chaining, fading, or modeling to name a few (e.g., Leslie, 2002).
Interestingly, modeling constitutes an important component of a significant number …