Table 1.

Relating model variables to biological examples.

	description	example	references
investment in discrimination (d)
perceptual abilities	ability to perceive and discriminate among differences in signal	detecting cuckoo eggs	[38]
learning/memory	acquiring and retrieving knowledge of signals	offspring recognition	[39,40]
pattern recognition	comparison of a signal against an internal template	species-specific song preference in crickets	[41]
cost of discrimination (e)
energetic costs	energy allocated to developing and maintaining tissue to detect signal	high energetic cost of brain tissue	[34,42]
tissue allocation costs	tradeoff costs of using tissue for recognition and not another purpose	paper wasps with individual recognition abilities have decreased the size of olfactory bulbs	[43]
sensory processing costs	neurological cost to processing and interpreting signal	extracting relevant information in noisy environments	[44,45]
detection costs	energy allocated to detecting signal	active sensing modifying behaviour to reduce stimulus ambiguity	[46,47]
investment in distinctiveness (v)
information content	the amount of information conveyed by the signal	facial colour variation in guenon monkeys	[48]
efficacy	the strength and/or reliability of the signal	environmental changes in chemical signals in lizards	[49]
cost of distinctiveness (f)
manufacturing costs	energy expended to manufacture signal	mouse major urinary proteins (MUPs)	[36]
byproduct costs	costs associated with other receivers detecting the signal	predatory bats eavesdropping on frog calls	[50]
opportunity costs	tradeoff costs of using signal for recognition and not for another purpose	tradeoff between individual recognition cues and quality cues	[27]
recognition costs	costs associated with being recognized by others	punishment of cheaters	[51]