Variables affecting alternation behavior in the cockroach,Blatta orientalis

To investigate alternation behavior in the cockroach as an invertebrate, three T-maze experiments were conducted assessing the effects of (a) intratrial (exposure) and intertrial (exposure to test) interval, (b) brightness similarity of the alternatives and response-direction factors, and (c) an initial free-choice vs. a varying number of forced-choice exposures. Alternation was enhanced with a long exposure on Trial 1, a short interval between Trial 1 and Trial 2 (test), greater dissimilarity (or discriminability) of the arm brightnesses and more frequent forced-choice exposures to an arm prior to test. These results highlight the role of intramaze brightness cues as controlling alternation in the cockroach and accord well with a response-to-change interpretation of the phenomenon. In addition, they suggest that the alternation paradigm can be used effectively to assay short-term memory storage in neurologically simple organisms.