Fig. 4. Results from the second-order conditioning control experiments. (A) Experimental time course as in the blocking experiment depicted in Fig. 3 (N=20). (B) Time course as in A, but with the duration of the unreinforced presentation of the compound stimulus reduced from 10 to 4 min prior to testing (N=22). Cross-hatched columns, training; open columns, test period; hatched columns, second-order training (no heat); shaded areas, compound stimulus; unshaded areas, single stimulus. Values are means ± S.E.M.