Complex sensory environments alter mate choice outcomes

Noise is a common problem in animal communication. We know little, however, about how animals communicate in noise using multimodal signals. Multimodal signals are hypothesized to be favoured by evolution because they increase the efficacy of detection/discrimination in noisy environments. We tested the hypothesis that female túngara frogs' responses to attractive male advertisement calls are improved in noise when a visual cue is added. We tested this at two levels of decision complexity (two and three choices). In a two-choice test, the presence of noise did not reduce female preferences for attractive calls. The visual cue of a calling male, associated with an unattractive call, also did not reduce preference for attractive calls in the absence of noise. In the presence of noise, however, females were more likely to choose an unattractive call coupled with the visual cue. In three-choice tests, the presence of noise alone reduced female responses to attractive calls and this was not strongly affected by the presence or absence of visual cues. The responses in these experiments fail to support the multimodal signal efficacy hypothesis. Instead, the data suggest that audio-visual perception and cognitive processing, related to mate choice decisions, are dependent on the complexity of the sensory scene.

噪声是动物通讯中普遍存在的问题。然而，目前学界对动物如何在噪声环境下借助多模态信号（multimodal signals）完成通讯的认知仍十分有限。演化假说提出，多模态信号会受到自然选择的青睐，因其可提升噪声环境下信号探测与辨别的效能。我们针对“添加视觉线索（visual cue）可改善噪声环境中雌性泡蟾对具有吸引力的雄性求偶鸣叫的反应”这一假说开展了验证。实验设置了两类决策复杂度水平：二选一与三选一任务。在二选一测试中，噪声的存在并未降低雌性对具有吸引力的鸣叫的偏好；无噪声环境下，与无吸引力鸣叫绑定的鸣叫雄性的视觉线索，同样未削弱雌性对优势鸣叫的偏好。但在噪声环境下，雌性更倾向于选择与视觉线索绑定的无吸引力鸣叫。在三选一测试中，仅噪声存在便会降低雌性对具有吸引力的鸣叫的反应，且该效应不受视觉线索有无的显著影响。本实验的结果并不支持多模态信号效能假说。与之相反，实验数据表明，与配偶选择决策相关的视听感知与认知加工过程，依赖于感官场景的复杂度。