INDUCTION OF COMBINATION RULES IN 2-DIMENSIONAL FUNCTION LEARNING

Previous studies have typically found that when people learn to combin e two dimensions of a stimulus to select a response, they learn additi ve combination rules more easily than nonadditive (e.g., multiplicativ e) ones. The present experiments demonstrate that in some situations p eople can learn multiplicative rules more easily than other (e.g., add itive) rules. Subjects learned to produce specified response durations when presented with stimulus lines varying in length and angle of ori entation. When stimuli and correct responses were related by a multipl icative combination of power functions, learning was relatively easy ( Experiment 1). In contrast, systematic response biases occurred during the early phases of learning an additive combination of linear functi ons (Experiment 2) and a more complex (nonadditive and nonmultiplicati ve) combination of linear functions (Experiment 3), suggesting that pe ople have a tendency to induce a multiplicative combination of power f unctions. However, the initial biases decreased with practice. These r esults are explained in terms of a revised adaptive regression model o f function learning originally proposed by Koh and Meyer (1991). Diffe rences between the present results and previous results in the literat ure are discussed.