Biomedical subjects

Magnus Enquist

Publications and source records attributed to Magnus Enquist.

4 recordsLinked to original sources

PubMed2004

Spots and stripes: the evolution of repetition in visual signal form.

It is common to find spatially repetitive patterns in animal visual signals. The evolution of such patterns is not well explained by existing theories of signal evolution. In this paper, we suggest that the evolution of signals with spatial repetition may be due to specific recognition problems and receiver biases. The logics of our hypotheses are studied in co-evolutionary simulations using artificial neural networks as models of receivers. These simulations yield repetitive visual signals under the following conditions: translations and reflections of the signal, partial obstruction of the signal, a fixed feature in the signal, and lateral inhibition in the receiver. In addition to regular repetitions our simulations sometimes result in other organisations of the signal such as blocky patterns and gradients.

Animals↗

PubMed2002

Spectacular phenomena and limits to rationality in genetic and cultural evolution.

In studies of both animal and human behaviour, game theory is used as a tool for understanding strategies that appear in interactions between individuals. Game theory focuses on adaptive behaviour, which can be attained only at evolutionary equilibrium. We suggest that behaviour appearing during interactions is often outside the scope of such analysis. In many types of interaction, conflicts of interest exist between players, fuelling the evolution of manipulative strategies. Such strategies evolve out of equilibrium, commonly appearing as spectacular morphology or behaviour with obscure meaning, to which other players may react in non-adaptive, irrational ways. We present a simple model to show some limitations of the game-theory approach, and outline the conditions in which evolutionary equilibria cannot be maintained. Evidence from studies of biological interactions seems to support the view that behaviour is often not at equilibrium. This also appears to be the case for many human cultural traits, which have spread rapidly despite the fact that they have a negative influence on reproduction.

Animals↗

PubMed2002

The evolution of signal form: effects of learned versus inherited recognition.

Organisms can learn by individual experience to recognize relevant stimuli in the environment or they can genetically inherit this ability from their parents. Here, we ask how these two modes of acquisition affect signal evolution, focusing in particular on the exaggeration and cost of signals. We argue first, that faster learning by individual receivers cannot be a driving force for the evolution of exaggerated and costly signals unless signal senders are related or the same receiver and sender meet repeatedly. We argue instead that biases in receivers' recognition mechanisms can promote the evolution of costly exaggeration in signals. We provide support for this hypothesis by simulating coevolution between senders and receivers, using artificial neural networks as a model of receivers' recognition mechanisms. We analyse the joint effects of receiver biases, signal cost and mode of acquisition, investigating the circumstances under which learned recognition gives rise to more exaggerated signals than inherited recognition. We conclude the paper by discussing the relevance of our results to a number of biological scenarios.

Animals↗

PubMed1998

Discrete conventional signalling of a continuous variable.

In aggressive interactions, animals often use a discrete set of signals, while the properties being signalled are likely to be continuous, for example fighting ability or value of victory. Here we investigate a particular model of fighting that allows for conventional signalling of subjective resource value to occur. Perfect signalling and no signalling are not evolutionarily stable strategies (ESSs) in the model. Instead, we find ESSs in which partial information is communicated, with discrete displays signalling a range of values rather than a precise one. The result also indicates that communication should be more precise in conflicts over small resources. Signalling strategies can exist in fighting because of the common interest in avoiding injuries, but communication is likely to be limited because of the fundamental conflict over the resource. Our results reflect a compromise between these two factors. Data allowing for a thorough test of the model are lacking; however, existing data seem consistent with the obtained theoretical results. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗