There is supporting research of the theory explaining that a phobia can be formed through Classical Conditioning from Watson and Rayner. They conditioned the fear of a white rat to which he was initially not afraid, in Little Albert by striking a steel bar to create a loud, unpleasant noise whenever Albert reached for the white rat. They used categories to measure the level of fear that Little Albert displayed: trembling lips, crying, crawling away so they were able to make comparisons with pre and post conditioning behaviour.