Fig. 1.

Diagram of behavioral apparatus in standard (A) and 90° mismatch (B) configurations. The circular track was composed of four different textured surfaces, each covering one-quarter of the ring: a gray rubber mat with a pebbled surface, brown medium-grit sand paper, beige carpet pad material, and gray duct tape with white tape stripes. The ring was centered inside a 9-foot-diameter black circular curtain. Hanging on the curtain or standing on the floor at the perimeter of the curtain were six objects (see Materials and Methods). Lighting was provided by a single 25 W bulb on the ceiling centered over the ring. In between recording sessions, the track was rotated CCW and the cues on the floor and curtains were rotated CW, as inB.