Mixed-modality psychophysical scaling: Inter- and intramodality sequential dependencies as a function of lag

Abstract

In mixed-modality psychophysical scaling, stimuli from different modalities are presented alternately for judgment on the same scale. This paper reports the results of two experiments using a variant of the standard technique that allowed investigation of inter- and intramodality sequential dependencies as a function of lag. Derived cross-modality matching functions from magnitude- and category-matching experiments were highly similar, with exponents around 1.6, as is the case for the standard technique. In both experiments, significant inter- and intramodality assimilation of responses to previous responses was found for lags of up to four trials back in the sequence of stimuli, whereas contrast of current responses to previous stimulus values occurred only within a modality, but also for lags of up to four trials. Second-order dependency of the correlation between current and previous responses as a function of the separation of their stimuli has the usual form (inverted v) for lags of up to four trials, both within and across modalities. Dependency of the coefficient of variation of the ratio of current to previous responses on the separation of their stimuli was found only within a stimulus modality, and only for a lag of one trial. These results strengthen the case for different sources for assimilative and contrastive sequential dependencies, and for the two second-order dependencies. © 1985 Psychonomic Society, Inc.