A psychologist watches the rapid eye movements of sleeping subjects. She wakes them and they report that they were dreaming. She concludes that dreams are linked to rapid eye movements. This conclusion is based on

The psychologist observed a correlation between REM sleep and dream reports through direct observation of eye movements. When subjects woke during REM and reported dreaming, she logically deduced that dreams occur during REM sleep periods. This is deduction from direct observation, not pure speculation or prior prediction.