Guest Q; Jim Dixon:
Unless US dictionaries are different, learned & learnt are not synoymous.
Learnt: (lurnt) is usually reserved for the past participle of the verb 'to learn', i.e. "he learnt his two times table"
Learned: (lurn'id) is the adjective to describe someone who has learning. "The learned gentleman taught his pupils English until they had learnt enough"

Nigel