Dietary and metabolic effects on rhesus social behaviour: neonatal thyroxine reductions

Assessment was made of the behavioural development of 3 monkeys whose levels of thyroxine were reduced by being given 131I and another 3 monkeys given a thyroxine depressant (TCAP) during the first weeks of life and maintained with low thyroxine levels for 3 months. When subsequently tested at normal thyroxine levels, these experimental subjects showed less positive social behaviour when compared with controls. When confronted with unfamiliar monkeys, the two experimental groups were less fearful than controls and also showed a lack of differential responsiveness in varying social situations, suggesting a low level of emotion. A foetal athyreotic group is also described.