Clever Hans, the famous horse who was believed to be able to count, is generally cited as the paradigm of the influence of the observer. Psychologist Rosenthal has illustrated this phenomenon with his well-known experiment about ‘bright’ and ‘dull’ maze rats. Hans, however, achieved something much more interesting. Hecould not only read human minds through their bodies: he could also influence his questioners to produce gestures he could read as cues for finding the answer. Hans could make human bodies be (...) moved and be affected, and move and affect other beings and perform things without their owners’ knowledge. The question of ‘influence’ when we read this case becomes therefore far more complicated and interesting. It involves the question of the way bodies can attune, affect and transformeach other. We may follow carefully how scientists of ethological practices create access to the creatures they study, how they are moved by their subjects of interest, and how they give them a chance to be interesting andto articulate other responses. Doing so, we notice that the signs that define subject and object, what talks and what is talked about, subjectivity and objectivity, are redistributed in a new manner. These practices offer a new and pragmatic definition of the body, close to James’s theory of emotions: to have a body is to learn how to feel. (shrink)