The evolution of index signals to avoid the cost of dishonesty

Jay M. Biernaskie, Alan Grafen, Jennifer C. Perry

Research output: Contribution to journalArticlepeer-review

74 Citations (Scopus)


Animals often convey useful information, despite a conflict of interest between the signaller and receiver. There are two major explanations for such ‘honest’ signalling, particularly when the size or intensity of signals reliably indicates the underlying quality of the signaller. Costly signalling theory (including the handicap principle) predicts that dishonest signals are too costly to fake, whereas the index hypothesis predicts that dishonest signals cannot be faked. Recent evidence of a highly conserved causal link between individual quality and signal growth appears to bolster the index hypothesis. However, it is not clear that this also diminishes costly signalling theory, as is often suggested. Here, by incorporating a mechanism of signal growth into costly signalling theory, we show that index signals can actually be favoured owing to the cost of dishonesty. We conclude that costly signalling theory provides the ultimate, adaptive rationale for honest signalling, whereas the index hypothesis describes one proximate (and potentially very general) mechanism for achieving honesty.
Original languageEnglish
Article number20140876
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1790
Publication statusPublished - 7 Sep 2014
Externally publishedYes

Cite this