ASSESSMENT OF PREFERENCE AMONG A RANGE OF OPTIONS USING LOG RATIO ANALYSIS

Animals generally exhibit preference from among the resources availabl e to them. Preference data are compositional, since they describe the proportion of some resource, such as time or energy, which has been al located to each option, and the sum of these proportions must be 1. Th e unit-sum constraint places a restriction on the types of analysis th at are appropriate. The method of log ratios provides a transformation that leads to analyses in which the unit-sum constraint is automatica lly satisfied. This paper describes a form of log ratio analysis that allows estimation of the relative preferences for the options availabl e and the influence on these preferences of the conditions under which the options are presented. The method is most suitable for applicatio n to data from controlled experiments in which options are presented i n pairs, as equal availability of rile choices can best be achieved an d standard regression techniques call be used to fit the proposed mode ls. The proposed analysis is demonstrated by a simple example in which the main difficulty of log ratio analysis, namely, unutilized options , is addressed and overcome.