Conditioning with delayed vitamin injections.

Rats deficient in thiamine were allowed to drink saccharin-fla vored water. They were then given an injection of thiamine which caused their intake of the nonnutritive fluid to increase. Delay of the intramuscular injection up to 30 minutes had no effect upon the acquisition of this condi tioning. Presumably, this delay reflects specialization in the central integrative mechanisms which serve these afferent modalities.

Cues: their relative effectiveness as a function of the reinforcer.

Two cues, either size or flavor of food pellet, were conditionally paired with either malaise induced by x-ray or pain induced by shock in four groups of rats. The combination of flavor and illness produced as conditioned decrement in consumption, but that of size and illness did not. Conversely, the combination of size and pain produced an inhibition of eating, but flavor and pain did not. Apparently, effective associative learning depends on central neural convergence of the paired afferent input.