Does multimodality per se improve receiver performance? An explicit comparison of multimodal versus unimodal complex signals in a learned signal following task

Multimodal signals are widespread in animal communication. Theoreticians have noted that, from an informational perspective, it is often not clear why multimodal signals should offer any benefit over unimodal complex signals. One possibility is that multimodal signals provide psychological benefits to receivers by virtue of the fact that they stimulate multiple sensory systems. Explicit comparisons of multimodal signals and unimodal complex signals are lacking, however. In this experiment, we examined the behavior of blue jays (Cyanocitta cristata) in a learned signal following task with two-component artificial signals that were either unimodal (visual-visual) or multimodal (visual-acoustic). We also manipulated the reliability of the components to verify that the subjects were able to follow each component type. We compared three measures of receiver performance—proportion of correct responses, learning rate, and reaction time. We found that while our subjects were able to follow both visual and acoustic signal components, performance did not differ in unimodal versus multimodal treatments.