Object permanence test
Lemurs
A majority of the lemurs were successful in the object permanence test, where four out of five lemurs reached the 70% learning criterion at a mean of 4.3 sessions.
The same four out of five lemurs also reached the 80% learning criterion at a mean of 6.8 sessions. Across the sessions, there was a significant increase in mean score (Spearman’s correlation test, rs=0.43, P<0.001).
Sakis
All four sakis were successful in the object permanence test, reaching the 70% learning criterion at a mean of 2.8 sessions.
Three out of four sakis also reached the 80% learning criterion at a mean of 4.3 sessions. In this species, however, there was no increase in mean score across sessions. (Spearman’s correlation test, rs=0.10, P>0.05).
