A key question in decision making is whether groups make better decisions than individuals [1–3]. This question is highly relevant to biodiversity conservation. For instance, individual experts may be consulted on management decisions or policy issues whereas boards of directors may make decisions on conservation donations and local communities may use group-based decision making for natural resource management. In the past two decades there has been a pronounced shift towards using groups instead of individuals for decision making (e.g., in key financial institutions such as the Bank of England ). Recently, it has also been suggested that groups should be preferred over individual experts for providing science advice to governments . These suggestions are often based on individual attempts to investigate the demerits and merits of group versus individual decision making. However, we are unaware of any studies that have compared group versus individual decision making in conservation. Moreover, there are no systematic reviews in any discipline on decision making by groups versus individuals (but see [1, 2, 6] for narrative reviews).
Thus far there has been very limited research on cognitive aspects of decision making in conservation [but see , though it has been studied extensively in other disciplines (e.g. social psychology). Conservation biologists typically approach decision making (and particularly conflict management) as biologists and not from a cognitive approach . Hence, it is not surprising that the literature on decision making in conservation revolves around short term economic incentives (e.g. payment for crop losses due to wildlife, payment for carbon [9, 10]) or technical solutions (e.g., changes in agri-environment schemes, prioritization aspects ) or even legal measures (e.g., laws on hunting in protected areas). There is also a considerable body of literature on structured decision making and adaptive management , and the cost-effectiveness of conservation decisions . Psychological biases or other cognitive aspects of the decision making process are rarely considered.
However, a review of 1048 business decisions, found that the process of decision making (e.g., level of participation) was more important (by a factor of six) than the analysis (e.g., detailed financial modelling) in determining the quality of decisions . Thus, psychological factors play a pivotal role in decision making and there is ample evidence to suggest that decisions are often influenced by the context in which judgements are made . In particular, decision making is fraught with psychological biases, as shown by the seminal work of Kahneman and Taversky . The impact of such biases in decision making is considerable and has been the subject of extensive research . Understanding these factors can have significant impact on improving the efficiency of the judgement process  and on furthering conservation goals  since efficient management interventions routinely require effective and rational decision making. Psychological aspects are particularly relevant for biodiversity decisions as they usually involve multiple stakeholders and often opposing viewpoints . The complexity in decision making is often exacerbated by the political nature of the decision itself (e.g., conservation of hen harriers ). Furthermore, the urgency within which decisions need to be made (e.g., in the face of a natural calamity) adds to this complexity.
Different facets of decision making (e.g., gender, type of task, effect of biases etc.) have been compared between groups and individuals over the years but the merits of each are unresolved. Attempts at collating and analysing the evidence on decision making by groups versus individuals are limited to narrative reviews which suffer from lack of documentation of the review process itself (see [1, 2, 6, 18]). They are thereby prone to being biased, subject to inter-reviewer differences and hence not repeatable. A systematic review can provide unbiased insights that cannot be obtained otherwise from individual empirical studies. This leads to the motivation for the present systematic review.
In this systematic review, we will attempt to assess when, where, and to what extent, are group decisions different from individual decisions. Are groups more rational or are they more error prone? Rationality refers to the rational choice theory in economics. Error refers to deviation of responses from the “true” value for questions where a “true” value is already known or can be easily calculated (e.g., intellective tasks).
The expected outcomes of the present review could be useful to a range of decision makers or to those who facilitate decision making in the real world. For example, both the International Union for the Conservation of Nature (IUCN) and the New Zealand Department of Conservation have structured their delivery of conservation advice through a series of specialist groups or teams, who collectively develop advice and inform decisions on particular taxa . Often these groups meet in person to define their advice. If the research reviewed here indicated that decisions made by individuals are actually more rational, or more likely to be correct than decisions made by groups, then these organisations might want to reconsider the group-based structure. Conversely, government policymakers often seek advice from independent experts individually . If our review finds that decisions made by groups are consistently more rational, or more likely to be correct, than those made by individuals, then such processes could be redesigned. Our results will be actively communicated to conservation NGOs and policymakers, through our direct involvement in a range of conservation-related science-policy interfaces and networks (for example, the Cambridge Conservation Initiative, and the Eklipse project ). In addition, the review might be useful to the theory and practice of decision making as traditionally studied in disciplines such as economics or social psychology.
Key concepts from other disciplines
While individual behaviour in decision making has received substantial attention , decision making in groups is relatively understudied. Some of the empirical research on groups tends to suggest that groups perform better than individuals in decision outcomes for selected biases, while others suggest that groups exacerbate selfishness and myopic loss aversion compared to individuals . Decision making by groups without any interaction can be vastly different from those in interactive face-to-face settings due to “groupthink”  and “egocentrism” effects [22, 23]. Groupthink refers to the phenomenon whereby individuals in a group tend to seek agreement, harmony and unity among the group members at the expense of independent critical thinking and individual better judgement. The tendency to be accepted as a good group member leads to acceptance of the majority solution that may not be evidence based or rational . Egocentrism refers to the situation where individuals falsely assume that their views are commonly agreed upon by the majority and they overestimate the consensus level . Investigating the differences between group versus individual decision making under a range of scenarios can improve our current understanding of the decision making process  and help reduce some of these biases.
Group versus individual decision making has been investigated for over four decades in several disciplines other than conservation (e.g., economics and social psychology), leading to significant advancements in these fields. For instance, in economics decision making has been extensively investigated under the paradigm of game theory. Typically these involve decisions in an interactive context where the outcome of a decision depends to a certain extent on the decisions of others. Game theory usually has some interesting assumptions, namely: (1) participants in a game have perfect knowledge of their interests and preferences, (2) participants have the ability to perfectly calculate the actions necessary to serve these interests, (3) participants are self-centred and care only about their own interests, (4) each participant has perfect knowledge of the rules of the game and knows that others are aware of 1–3 above.
If all these assumptions are valid, then each participant’s behaviour in most games (e.g., Prisoner’s Dilemma) can be predicted by a “rational benchmark” (e.g., Nash Equilibrium) . This also makes it easier to calculate deviations from such rational benchmarks. However a sizeable volume of research has questioned these assumptions . Thus, though game theory can act as a normative theory to estimate rational decision making (or deviations thereof), it falls short of being a descriptive tool. The deviations are often influenced by biases and form the fodder for investigation of social psychologists. In addition, research on collective action may be a good predictor of deviations from rational theory. Rational theory traditionally uses self-interested decisions and thresholds, such as Nash equilibrium, to judge individual decisions. These assumptions may not hold in the context of collective action where the objective is to maximise the group goal or group objective (which may be different from individual goals or objectives).
In social psychology, group research (particularly on small groups) has focussed on group performance for a variety of tasks (e.g., letters to numbers problem, mathematical tasks) and the processes by which the decision is arrived at (e.g., discussion versus no discussion, aggregation of responses, decision rules used, information processing) (see review [2, 24]).
Both intellective and judgemental tasks are interesting from a conservation perspective as practitioners routinely engage in making decisions that cognitively rely on either task (or both). For instance, consider the decision to invest in a guided busway as opposed to a bike lane in a city. Both might contribute to reducing carbon emissions by providing alternate modes of traffic compared to cars. While deciding on the basis of quantitative evidence available with respect to costs and feasibility may be intellective task, the final decision may rely on the “buy in” and prioritisation by different stakeholders engaged in making the decision (a judgemental task).
Research on conservation decision making is relatively in its nascent stage in conservation and much remains unknown. The advances in other disciplines could provide critical transferable knowledge for conservation. To avoid past mistakes, and to facilitate better decision making in conservation, an interdisciplinary comparison of decision making in different disciplines could be critical.