Small-magnitude (2-3 beats per minute) heart-rate responses can show sex differences if assessed with a psychophysiological approach in which temporally fine-grained methods are used to determine topographical differences. Such differences emerged when 15 males and 37 females were shown videosegments depicting emotional scenes. Specifically, males accelerated to erotic segments (couples making love), while females accelerated to segments showing babies crying. In addition, the peak development of baby-cry-elicited accelerations occurred about 1 second before that of erotic segment-elicited accelerations. The results are consistent with a preparatory-response interpretation, but more research is needed both to investigate the generality of these sex differences in heart-rate responses, and to determine the role of experiential and psychosocial factors.