The Concise Oxford Dictionary of Current English (Allen 1990) states that to compartmentalize is to ‘divide into components or categories’. In the context of the study of animal consciousness, compartmentalization may be considered to be an attempt to disregard certain beliefs in particular circumstances; to think about the same issue in different ways depending upon the context. For example, Fraser and Broom (1990) state that ‘the assessment of [animal] welfare can be carried out in a scientific way without the involvement of moral considerations … the process of deciding about morality and the process of assessing welfare are quite separate’. Yet is this proposed ‘switching on and off of beliefs in different contexts appropriate, let alone possible? Many animal scientists also use animals, and in doing so assume their animals are conscious. This assumption influences their interaction with them. It is not possible to ride a horse competently, for example, without assessing how it ‘feels’ about the signals one is transmitting; whether they are making the horse irritated, or whether it is calmly accepting them. Good riders, whether aware of it or not, are those who are sensitive to the horse's reactions to their movements. Recognized expressions of the horse's ‘feelings’ when ridden include rounding of the posture in the excited horse (Mills & Nankervis 1999) and shying in the frightened horse (Fraser 1992). In crediting animals with consciousness as an animal user, it is surely not logical to assume they are not conscious when behaving as a scientist. Thus compartmentalization may be an illogical attempt at parsimonious oversimplification, which is essentially contradictory to one's practical experience of animals, and therefore a hindrance in attempting to assess animal consciousness. Of course anthropomorphism must be avoided; it has limited value in the scientific study of animal behaviour and welfare. Furthermore, it could be considered demeaning to animals to assume that consciousness could only take the form that humans experience; that they are ‘humans in animal suits’. Yet it is equally wrong to ignore the logical objections to compartmentalization.