Fig. 1.

Pacing chambers used to assess female sexual behavior in the present experiments. (Upper) Copulation in bilevel chambers, initiated by solicitation (1), followed by anogenital investigation of the female (2), a runaway by the female to the other level (3), enticing the male to chase her, and finally the display of lordosis by the female (4), which allowed the male to mount with vaginal intromission. (Lower) Copulation in unilevel pacing chambers. The female on the left is crawling through a hole in a central partition to initiate copulation with the male. The female on the right has just been mounted.