The Morton-Massaro law of information integration: Implications for modelsof perception

Information integration may be studied by analyzing the effect of 2 or more sources (e.g., auditory and visual) on participants' responses. Experiment s show that ratios of response probabilities often factorize into component s selectively influenced by only 1 source (e.g., 1 component affected by th e acoustic source and another 1 affected by the visual source). This is cal led the Morton-Massaro law (MML). This article identifies conditions in whi ch the law is optimal and notes that it reflects an implicit assumption abo ut the statistics of the environment. Adherence to the MML can be used to a ssess whether the assumption is being made. and analyses of natural stimuli can be used to determine whether the assumption is reasonable. Feed-forwar d and interactive models subject to a channel separability constraint are c onsistent with the law.