RATIO VERSUS DIFFERENCE COMPARATORS IN CHOICE

Several theories in the learning literature describe decision rules fo r performance utilizing ratios and differences. The present paper anal yzes rules for choice based on either delays to food, immediacies (the inverse of delays), or rates of food, combined factorially with a rat io or difference comparator. An experiment using the time-left procedu re (Gibbon and Church, 1981) is reported with motivational differentia ls induced by unequal reinforcement durations. The preference results were compatible with a ratio-comparator decision rule, but not with de cision rules based on differences. Differential reinforcement amounts were functionally equivalent to changes in delays to food. Under biase d reinforcement, overall food rate was increased, but variance in pref erence was increased or decreased depending on which alternative was f avored. This is a Weber law finding that is compatible with multiplica tive, scalar sources of variance but incompatible with pacemaker rate changes proportional to food presentation rate.