Behaviours evoked by optogenetic activation of ChR2-expressing Esr1cre/+ males at the indicated photostimulation frequencies are plotted (5, 10, and 20 Hz). Different photostimulation intensities were applied in different episodes (coloured lines). In each episode, photostimulation frequency was varied at a fixed intensity. Only 2/14 stimulation episodes (orange) exhibited a behavioural shift from mounting to mixed to attack behaviours with increasing photostimulation frequency. Data from n = 11 animals.