For decades, researchers and practitioners have attempted to find evidence for a personality stereotype in individuals with Down syndrome that includes a pleasant, affectionate, and passive behaviour style. However, a more nuanced exploration of personality-motivation in Down syndrome reveals complexity beyond this pleasant stereotype, including reports of a less persistent motivational orientation and an over-reliance on social behaviours during cognitively-challenging tasks. It is hypothesised that the personality-motivation profile observed in individuals with Down syndrome emerges as a result of the cross-domain relations between more primary (cognitive, social-emotional) aspects of the Down syndrome behavioural phenotype. Young children with Down syndrome show a general profile of delays in the development of instrumental thinking coupled with emerging relative strengths in social-emotional functioning. If it is true that a less persistent motivational orientation emerges as a secondary phenotypic result of more primary strengths in social functioning and deficits in instrumental (means-end) thinking, it may be possible to alter the developmental trajectory of this personality-motivation profile with targeted and time-sensitive intervention. Implications for intervention planning are discussed.