Maximum Likelihood Difference Scaling versus Ordinal Difference Scaling of emotion intensity: a comparison

We compare the utility of Maximum Likelihood Difference Scaling (MLDS) and Ordinal Difference Scaling (ODS) for the measurement of emotion intensity. MLDS and ODS are both nonmetric probabilistic scaling methods based on difference measurement; however, MLDS uses quadruple comparisons (comparison of pairs of stimulus pairs) as input data, whereas ODS uses graded pair comparison judgments, where participants indicate the size of the difference between two stimuli on an ordinal response scale. In two studies using different kinds of emotional stimuli (disgust-inducing pictures, and descriptions of situations eliciting relief), quadruple comparisons and graded pair comparisons of the stimuli were collected and submitted to MLDS and ODS respectively. The scaling solutions were compared in terms of the reliability of the estimated scale values and their correlations to direct ratings of emotion intensity. The findings of both studies suggest that ODS performs at least as well as MLDS on these criteria. In addition, in most cases, good to high agreement between the scale values estimated by the two methods was found. Hence, ODS may be used as an economical alternative to MLDS for the difference scaling of emotional stimuli.