In order to measure time perception, Barkley et al. (1997) developed two rating scales to evaluate children's sense of time and their ability of time management. They found an association between ADHD and poor time management. Barkley's (1998) comprehensive model suggested that time perception deficits in children with ADHD are due to deficits in behavioral inhibition and executive functions. Barkley et al's time reproduction tasks showed that children (1997), adolescents and young adults (2001) with ADHD had significantly more errors.