Eight pigeons were trained on concurrent variable-interval variable-interval schedules with a minimum interchangeover time programmed as a consequence of changeovers. In Experiment 1 the reinforcement schedules remained constant while the minimum interchangeover time varied from 0 to 200 s. Relative response rates and relative time deviated from relative reinforcement rates toward indifference with long minimum interchangeover times. In Experiment 2 different reinforcement ratios were scheduled in successive experimental conditions with the minimum interchangeover time constant at 0, 2, 10, or 120 s. The exponent of the generalized matching equation was close to 1.0 when the minimum interchangeover time was 0 s (the typical procedure for concurrent schedules without a changeover delay) and decreased as that duration was increased. The data support the momentary maximizing theory and contradict molar maximizing theories and the melioration theory.

In a recent attempt to translate several papers for Brazilian publication, the present writers were confronted with the problem of selecting suitable Portuguese equivalents of terms commonly used in English-language studies of operant behavior. We felt a special responsibility in this task since, to our knowledge, there were no more than one or two instances of such terminology in this country (e.g., Rocha e Silva, 1961). We were bandeirantes (= pioneers) in the field! Many items in the present tentative list of translations were the result of our attempt. Others came after we had consulted the papers on French and German translations (Richelle, 1960;Schaefer, 1960)