They know the face that feeds them

Pigs recognise humans who feed them

source: New Scientist June 16 2001 p25

Researchers from Hiroshima University, Japan, have found that pigs can recognise people who feed them. They trained pigs to go towards people wearing boots, gloves and overalls, with food rewards. The pigs were then faced with a choice of two people, both dressed the same way, and sitting behind screens at waist level. The pigs went towards the person who had originally fed them, even when perfume was used to mask the smell of the researchers, or when they hid part of their faces. This research was reported in Applied Animal Behaviour Science, vol 73, p45