A new theory for animal communication

Their aim was to integrate the existing theoretical ideas and generate a new general signalling theory that offers testable predictions for researchers studying animal communication and sexual selection

Cancelling the handicap principle

For decades, the leading theory to explain honest signals has been the handicap principle, which asserts that to be honest, signals must be costly to produce. A costly signal supposedly demonstrates that a signaller is in good condition and has energy to waste, whereas poor quality individuals cannot afford the investment necessary to develop and maintain costly, wasteful ornaments. However, in 2020, Dustin Penn and Szabolcs Számadó explained why this idea can and should be rejected, and how the so-called 'costly signalling' models that led to its acceptance were misinterpreted. Honesty in these models evolves – not because signalling is costly or wasteful – but because honesty is beneficial and deception is costly.

Unhandicapping honest signalling models

In their recent paper, Penn and his collaborators propose a new general theory to explain both honest and dishonest signals. They first explain why a new theory is needed by summarizing the problems with the handicap principle and handicap interpretations of signalling models. They re-evaluate these theoretical models and show how they can be re-interpreted to avoid the misleading and confusing handicap principle. In short, these models are based on signalling trade-offs (and opportunity costs), and not actual signalling costs. Penn acknowledges that their main points may seem like semantic quibbling", but he argues that "our interpretations better clarify how signalling models work and what they predict".

In addition, the authors examine other hypotheses proposed to explain honest signals and they propose how these seemingly unrelated ideas are all based on signalling trade-offs. Finally, the authors suggest that trade-offs are also central for explaining deceptive signals. The authors point out that previously efforts to explain honest signals have oddly ignored deception and never proposed an explanation.

The new theory is relevant to the social sciences, as well as biology, since costly signalling theory has also been the leading theory for honesty in humans. Penn points out, "One of the major problems of our times is explaining the rise of misinformation and disinformation (known as the infodemic) and one of our goals is to help find ways to improve the reliability of communication."

Penn explains that "the handicap principle and costly signalling models provide an example of the ongoing 'theory crisis' in the biological and social sciences, generated by researchers attempting to empirically test vague verbal theories or mathematical models that are misinterpreted or poorly explained, which allows for many possible interpretations.  Their aim is to generate a new theory with clear and testable predictions.

The article "A general signalling theory: why honest signals are explained by trade-offs rather than costs or handicaps" by Szabolcs Számadó, István Zachar and Dustin J Penn was published in Journal of Evolutionary Biology. 

Scientific article

Scientific contact:
Priv.-Doz. Dr. Dustin J. Penn
Konrad Lorenz Institute of Ethology
University of Veterinary Medicine Vienna
dustin.penn@vetmeduni.ac.at