Fig 1. Experimental apparatus.

During demonstrations, observer calves were restricted in the central pen and demonstrators were restricted in treatment pens (with either red squares or blues triangles on the walls). One demonstrator was recovering from a painful procedure (sedation, local anesthesia and hot-iron disbudding) and the other from a sham procedure (sedation alone). During test sessions gates were removed, and observers were assessed by themselves for conditioned place aversion. Illustration by Ann Sanderson.