Cross-modal facilitation of auditory discrimination in a frog

Abstract

Stimulation in one sensory modality can affect perception in a separate modality, resulting in diverse effects including illusions in humans. This can also result in cross-modal facilitation, a process where sensory performance in one modality is improved by stimulation in another modality. For instance, a simple sound can improve performance in a visual task in both humans and cats. However, the range of contexts and underlying mechanisms that evoke such facilitation effects remain poorly understood. Here, we demonstrated cross-modal stimulation in wild-caught túngara frogs, a species with well-studied acoustic preferences in females. We first identified that a combined visual and seismic cue (vocal sac movement and water ripple) was behaviourally relevant for females choosing between two courtship calls in a phonotaxis assay. We then found that this combined cross-modal stimulus rescued a species-typical acoustic preference in the presence of background noise that otherwise abolished the preference. These results highlight how cross-modal stimulation can prime attention in receivers to improve performance during decision-making. With this, we provide the foundation for future work uncovering the processes and conditions that promote cross-modal facilitation effects.

Keywords: comparative psychology; multi-modal communication; multi-modal integration; multi-sensory processing; túngara frogs.

Figure 1.

(a) Experimental set-up. (b) RoboFrog with an inflated silicone vocal sac. (c) The RoboFrog controller. See methods and electronic supplementary material for additional details.

Figure 2.

(a) A bar graph from experiment 1 demonstrating that the combined visual and seismic stimulus causes the largest effect. The y-axis indicates the percentage of females that chose the multi-sensory stimulus over the unisensory stimulus. For all conditions, an identical whine chuck (complex call) was played from both speakers. (b) A bar graph from experiment 2 depicting significant cross-modal facilitation. The y-axis indicates the percentage of females that chose a whine chuck (complex call) over a whine (simple call). For all conditions, the only difference between the choices was in the acoustic modality. For (a,b), error bars indicate 95% confidence intervals from binomial tests, with darker bars and asterisks above bars indicating conditions significantly different from chance (50% dashed line). Asterisks with horizontal lines indicate significant differences between conditions from GLMMs. Numbers at the bottom of each bar indicate the sample size.