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nch tre Spotlightsfemales decreased their sniffing rate specifically when engaged in face-to-face interactions (and not flank or ano-genital investigation) with a dominant conspecific. To understand what this might mean, let us first con-sider other forms of social communication in the rat. A well-studied example is the ‘social transmission of food preference’, in which the safety of a given food is signalled to a naı̈ve conspecific. The signal is mediated by the conjunction of carbon disulfide (CS2) and the odour of recently eaten food in the demonstrator’s breath [6]. similar to a belly-up posture, that might help to reduce the cost of an encounter with a dominant conspecific. However, it is important to consider that sniffing rate has also been shown to reflect important aspects of the physiological state of the animal, much as heart and respiration do. Sniffing is modulated by reward expecta-tion [10], a relationship that might reflect the modulation of respiratory rate by neuromodulators that coordinate physiological responses to salient events, such as an en-counter with a dominant conspecific. Thus, it would be important to understand whether the lowering of sniffing frequency is coupled to a general state change induced by aCorresponding author: Mainen, Z.F. (zmainen@neuro.fchampalimaud.org).Social cognition in the rod