A strength is that Bowlby’s (1944) 44 thieves study supports the idea that maternal deprivation increases the risk of criminality. 12 out of the 14 of the juvenile offenders that displayed signs of affectionless psychopathy also had experienced early separation from their mothers. However, this study is retrospective and relies on self-report data, which may be biased or inaccurate. Additionally, Lewis (1954) found no clear link between maternal deprivation and offending, suggesting the relationship may not be as strong as Bowlby claimed.