Many farmers will agree that pigs can show quite extraordinary cognitive abilities. New research from the University of Cambridge suggests that pigs show awareness when exposed to a mirror test. Pigs with prior experience of mirrors seemed to realise that they were looking at a mirror image and correctly searched for a hidden food bowl seen in the mirror away from the mirror, while pigs with no prior experience searched for the food bowl behind the mirror.


Awareness is a difficult thing to study or even to define. Traditional it is defined as the ability to perceive, to feel and to be conscious, but this definition is very difficult to measure. Thus while we can be fairly certain that we ourselves are aware, we can be less certain that our friends are aware but at least they can tell us so. Animals cannot. However, there is one way to assess the self-awareness in animals and human infants. Put them in front of a mirror and looks for signs that they recognise themselves. When human infants are exposed to mirrors age and then fooled to think that a video playback of themselves with a sticker on their head was a mirror, 0% of two year olds, 25% of three year olds and 75% of four year olds reached for the sticker. 

Many animals has similar been shown to recognise themselves and objects in mirrors or videos. Prof. Broom and co-workers from the University of Cambridge has now published a study in Animal Behaviour that suggests that pigs too can correctly use information obtained from mirrors.  

The researchers put individual pigs in a pen with a mirror at one end in which they could see a food bowl that was otherwise hidden behind a barrier. Two groups of pigs were then compared. The first group had no prior experience with mirrors while the other group had been exposed to mirrors in pairs (but without any hidden food bowl) for 5 hours prior to the experiment to allow them to associate reflections in the mirror with their own and their companions’ movements.

Of the 11 pigs that had no prior experience to a mirror, 9 moved towards the mirror and searched for the food bowl behind the mirror, while 7 out of 8 experienced pigs moved away from the mirror and correctly located the food bowl.

Thus the study suggests that pigs are able to understand that they look at reflections of themselves and objects in a mirror and correctly move their own body in the real world to successfully locate an object only visible in the mirror. In order to do this they must somehow have been self aware.

Broom, D. M., Sena, H. and Moynihan, K. L. (2009) Pigs learn what a mirror image represents and use it to obtain information. Animal Behaviour 78: 1037-1041.