Table 2.

Hypotheses to explain the benefits of the use of complex cues and their underlying assumptions

Hypothesis	Underlying assumptions
1. Complex cues can prevent information loss in variable environments	(i) Simple cues are significantly compromised in variable environments. (ii) This loss of information Leads to phenotypes mismatched to the environment. The resulting deleterious effects reduce fitness and hence exert selection for processing complex rather than simple cues. (iii) Cue components can convey equivalent information and are interchangeable to the extent that the overall message is intact if one or more components are compromised.
2. Complex cues can fine-tune plastic responses based on multiple features of the environment	(i) Cue components provide at least partially different information. (ii) Perception of a greater quantity of environmental information results in a better phenotype-environment match.
3. Complex cues can reduce time lags between environmental change and response	(i) Sensory thresholds for initiating responses exist. (ii) Complex cue components additively or synergistically contribute to meeting these thresholds. (iii) The information transferred by each cue component is correlated. (iv) A fast-responding phenotype confers adaptive benefits. (v) These benefits outweigh potential costs of changing the phenotype in response to an ephemeral environmental fluctuation.
All the above	(i) Genetic and phenotypic variation in ancestral populations existed, upon which natural selection acted to promote the processing of complex cues. (ii) Organisms have the sensory and cognitive capacity to receive, process and integrate more than one cue component. (iii) The production of complex cues either Directly benefits the signaller, or occurs for other purposes and is co-opted by the receiver. (iv) A phenotype that is more closely matched to the social/sexual environment confers fitness benefits. (v) These benefits outweigh the potential costs of processing complex cues.