There are also physical changes which are caused by emo- tions and are regarded as signs of them, such as blushing with shame and shivering or turning pale with fear. 59 Aristotle assumes that such visible bodily changes are physically caused by the small expansions and contrac- tions of the heart, the centre of psychic activities. These primary changes, which are produced by heating and chilling, are not perceived, but may cause large-scale emotional expressive movements and initiate intended action (MA 7, 701b24–32). The heating and chilling of the heart may be caused by perceptions, imagination, or thought (MA 7–9). 60 These cardiac movements are also associated w ith the expansion or contraction of the connate pneuma, an airiform substance, due to the changes of the vital heat in the hear t (MA 10). 6