No casual findings- All that is established is a relationship between the variables which are prolonged seperatipn and emotional problems. There may be other variables that cause emotional problems such as discord among the family that caused prolonged separation. It could be that affection less characters caused separation this means no casual conclusions should be drawn
M+P
Biased data - Bowlby produed a rich record of qualitative data on each of his participants based on interviews with children and families . 25 pages of report detailing the case histories of 44 thieves. Data is limited as it’s based on view of one person ( albeit a very experienced psychologist ) His perception may have been biased by his own beliefs ( his belief in importance of early experience ) and
M+P Sample
All 88 children are emotionally disturbed therefore it may not be appropriate to generalise from this sample to all children ( there may be delinquents who are not emotionally disturbed as there delinquency may be more social than emotional )
Alternative Evidence
One criticism is bowlby muddled togeter several different experiences. Separation alone may not cause long lasting damage especially if a child is given a good substitute emotional care. Furthermore research as shpwn there is a sensitive period of development a lack of emotional care effects age 6 appears to be sorting children can recover from ( seen in a case of Romanian orphans) and
Alternative Evidence Strength
Bowlbys basic conclusion has been supported in subsequent research . Lack of emotional care during key periods of development appears to ace lasting and serious consequences. This includes physical underdevelopment intellectual retardation