Evidence for comparative decision making in female crickets

Acoustic communication signals are often involved in mate-choice decisions. The decision for the best mating partner can become difficult when the available parameters of a signal are not positively correlated. Rational choice theory predicts that animals assign each signal a fixed value on a single dimension. The probability of choosing one signal over the other should be a monotonic function of the respective values and result in transitive choices. A violation of transitivity in choice behavior would suggest comparative rather than absolute decision making. Here, we tested the transitivity of preferences of female crickets for male calling songs. We conducted a series of binary choice experiments and compared their outcome to female preferences measured in no-choice experiments. To test transitivity, every choice pair had to differ in 2 parameters of the calling song. The parameter pairs used were 1) pulse rate and sound intensity, 2) chirp rate and sound intensity, and 3) pulse rate and chirp rate. The results revealed that females acted transitively if chirp rate and sound intensity or pulse rate and chirp rate of the patterns were varied. But females violated transitivity if pulse rate and sound intensity of signals differed as they mostly chose the louder pattern, although it was less attractive in the no-choice situation. This implies that sound intensity was weighted differently by females in the decision process in no-choice and choice experiments. The violation of transitivity suggests a comparative evaluation of available signals by female crickets.