evaluation of schaffer and emersons study
+ the data was collected by observation from the mothers or from the mothers themselves. both are high in bias and inaccuracy.
+ it has slight realism as it ws conducted under everyday conditions meaning that the conclusion can be seen as having high validity
-there was a lot of individual differences in when the attachments were formed which puts doubt on the proces of the forming of attachments being solely biological
+ babies lack demand characteristics, higher validity