Psychology is an empirical science.
Knowledge about behavior must, in so far as possible, be based on objective observation, evidence, and data. Assumptions and inferences should be avoided, and great care should be taken to limit ones conclusions about behavior to what we have observed rather than forming interpretations of what we have observed. If observers were asked to record what they had seen while watching others, statements such as the ones that follow might have been recorded. The man in the drugstore fell to the floor clutching his chest and the other customers turned in his direction when he screamed. The pigeon which had been pecking at the disk was distracted by the sound of the door slamming, and it hesitated while it considered whether to keep pecking or not.