Cats were exposed to 0.5 to 1.0 g silver vine powder (corresponding to 1–2 packets as sold by the manufacturers) inside a thin, porous sock (sock hereinafter), or 0.5 to 1.0 g silver vine powder spread out on approximately 500 square cm of a piece of 0.5 square m of Frieze carpet (carpet hereinafter). This type of carpet was used because it allowed more direct exposure to the materials than did the socks, while still minimizing the ability of the cats to ingest the plant material. Equal volumes of catnip (5 g), valerian root (15 g) and Tatarian honeysuckle sawdust (15 g) were offered inside a sock. This amount of plant material filled the sock about half full, and allowed tying a knot to close off the sock. Tatarian honeysuckle also was offered as an approximately 10 cm long piece of wood (Fig. 2a).