Give two criticisms of Bowlby's 44 thieves study

One major issue with the research conducted by John Bowlby is that there is bias and subjectivity in his findings. Bowlby's theory of maternal deprivation was constructed prior to the research being carried out. Consequently, Bowlby's research is likely to have been interpreted in a way which supports his own theory and would be very subjective. This suggests that the research is not valid and is a weakness of his findings.Another issue is that of inferring causation from correlation. Bowlby's study was primarily observational and so extranious variables could not be controlled. Furthermore, the research was conducted after the 44 thieves had committed their crimes, consequently Bowlby cannot determine whether the criminal tendencies began as a result of maternal deprivation. This further weakens the validity of Bowlby's findings and the overall study.