Data from: Cabrera-Álvareza, M.J., Swaney, W. T. & Reader, S. M. 2017. Forebrain activation during social exposure in wild-type guppies. Physiology & Behavior, 182, 107-113. The data are in two csv files. Please see the paper for additional details. NeuronalData_Cabrera-AlvarezSwaneyReader_2017_ForebrainActivationDuringSocialExposureInWild-typeGuppies_PhysiologyAndBehaviour.csv : Neuronal IEG expression counts (mean number of neurons per 100µm2) of 35 female guppy subjects (Fish ID) of wild Trinidadian origin, that were exposed to one of three treatments (0: isolated fish; 2: exposed to 2 companion fish; 10: exposed to 10 companion fish). We counted the number of neurons expressing egr-1 in each hemisphere of four brain areas (POA – Preoptic Area; Vd – Dorsal part of the ventral telencephalon; Vv – Ventral part of the ventral telencephalon; Vs – Ventral pallium) and calculated the mean of the two hemispheres. BehaviouralData_Cabrera-AlvarezSwaneyReader_2017_ForebrainActivationDuringSocialExposureInWild-typeGuppies_PhysiologyAndBehaviour.csv : Data on the behaviour of 30 female guppies (Fish ID) of wild Trinidadian origin. These are different fish to the subjects reported in the NeuronalData file. These guppies were placed in a tank with a shoal of 2 other females in one end and 10 other females in the other end and their behaviour was measured for 10 minutes. The column called ‘Shoaling’ represents time the subjects spent in close proximity (3 to 4 body lengths) of the large shoal minus the time in close proximity to the small shoal. The column called ‘Interactions’ (i.e. swimming head first against the transparent partitions) represents the time spent interacting with the large shoal minus the time spent interacting with the small shoal. Time is reported in seconds.