Institute of Neuroscience

Staff Profile

Dr Gilbert Roberts

Senior Lecturer


Evolution of Cooperation

Cooperative behaviour can seem paradoxical given the focus on self-interest and competition in both evolutionary theory and economics. Yet cooperation is better seen as a fundamental process in evolution, underlying the major transitions to complex life and to sociality. Cooperative behaviour is key to the success of human societies, and is found in many other animal species. My research programme focuses on explaining how cooperation works, and on why humans appear to be such a cooperative species. I take a cross-discipline approach combining theoretical and modelling work with fieldwork and experiments on humans and other animals. My main interests include the following.

Reputations, Partner choice and Competitive Altruism

A concern for reputation is a distinctive feature of human cooperation: we are more cooperative when we are observed and we favour those who cooperate. The concept behind my theory of Competitive Altruism is that by cooperating we are investing in a reputation which brings us longer term benefits. Research in my group provided the first experimental evidence for competitive altruism: people tend to be more cooperative when their behaviour is public and they have an opportunity to choose partners. This finding has since been replicated by other authors. We have also demonstrated that reputation building pays through access to more profitable partnerships.  The key idea underlying CA is that partner choice actually drives cooperative displays - in other words we may be more cooperative than the economics of a game would suggest: this takes us into the territory of signalling behaviour.

Cooperation as a Signal

My theoretical work on why we care how we are seen by others suggests that reputations provide honest signals of intentions to engage in cooperative relationships, as opposed to costly signalling.

Can Indirect Reciprocity explain Reputation-Building?

Competitive altruism provides a more generally applicable and stronger explanation for reputation-based cooperation than indirect reciprocity.

Altruism as a courtship display

We have also provided the first evidence for competitive altruism in a mate choice context: people are more cooperative with more attractive members of the opposite sex, and cooperating makes you more attractive.

Do "watching eyes" increase cooperation?

Following on from Haley & Feslsler's demonstration that eye cues on a computer screen can make people more cooperative, we have carried out a series of studies replicating this effect in various naturalistic settings. For example, coffee drinkers are more likely to contribute to an honesty box when eye images are present, while shoppers are more likely to donate to charity given eye sybols on collecting tins.

Why do people punish others and can this help solve the problem of cooperation in groups?

Punishing others provides a potential solution to the problem of cooperation in groups. I have shown that using parameters typical of behavioural economic games, punishers can make a net profit, removing the dilemma. Furthermore I show how the dynamics fit a 'producer-scrounger' game whereby it can pay some individual to contribute even if others do not.

Cooperation through Interdependence

A key problem in explaining cooperation is that while it may pay well, exploiting a cooperator may pay even better. However, I argue that interdependence is an important factor facilitating cooperation because cooperators benefit as a by-product of helping their recipients. Helping can then be favoured when its costs are outweighed by the altruist’s stake in the recipient’s benefits. I have shown how defining an individual’s ‘stake’ in another corresponds to Hamilton’s rule. The direct benefits of cooperation, even when there is no reciprocation, are now being seen as increasingly important.



JIF/Wellcome Trust
Arts Council/AHRB


I previously served on the Council of the Association for the Study of Animal Behaviour as Newsletter Editor and set up a website for ASAB at

Postgraduate Supervision

Billie Dee Moffatt

Karolina Sylwester completed a PhD on the role of reputation in human cooperation and went on to a postdoc on punishment at Bath.

Daniel Farrelly's PhD thesis from 2005 entitled "Courtship, reputation, biological markets and the evolution of cooperation: A study using computer-mediated communication" presented some of the first experimental evidence for competitive altruism, sexual selection and market effects on cooperation. Daniel is now lecturer in Psychology at Sunderland.

Conferences & Talks

Reviewing / Editing


Undergraduate supervision

Empirical Projects

Masters Supervision

MRes Animal Behaviour; Evolution & Human Behaviour Projects

Courses Taught


Sex and Human Nature

Evolution of Behaviour

Cognitive Psychology

Statistics for Psychologists

Animal Behaviour

Social Psychology

Psychology Practicals

Animal Behaviour Practicals

Administrative Responsibilities

Personal Tutor

Joint Honours Advisor

Departmental Web-site Manager

Honours Project Coordinator

Secretary to Board of Examiners

Chair of the Board of Examiners

Stage 3 Tutor

Teaching and Support Committee

Psychology Brain and Behaviour Executive