Why personality differences matter for socialfunctioning and social structure

Max Wolf and Jens Krause

Department of Biology and Ecology of Fishes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Mueggelseedamm 310,

12587 Berlin, Germany

Spotlight

We outline three main ways how personality differencescan affect social functioning and social structure. Byhighlighting the broad and significant consequencesthat personality differences can have for social process-es, our article might serve as a starting point for aresearch focus that aims at a systematic understandingof these consequences.

Personality differences and social processes: a two-wayinteractionPersonality differences, between-individual differences inbehaviour that are consistent over time, are widespread inthe animal kingdom. Over the last years, much researchhas focussed on the ecological and evolutionary causes ofsuch differences. A key result of this research is that avariety of social processes such as frequency-dependentselection, reputation-building, or social niche specialisa-tion have been found to be important factors causing theemergence of personality differences within populations[1]. However, this is only one side of the coin. While socialprocesses can cause personality differences, the existenceof personality differences can be expected to have substan-tial consequences for social processes within animal groupsand populations. In our view, this latter issue has receivedfar too little attention in the past. What are the conse-quences of personality differences for social functioningand social structure? We here provide a first conceptualframework for a research focus centred on this question. Inparticular, we outline three main ways in which personali-ty differences can affect social processes at different levelsof social organisation (see Table 1 for a brief summary).

Social responsiveness, behavioural coordination andsocial competitionFirstly, the presence of personality differences withingroups and populations is predicted to promote the emer-gence of socially responsive individuals, that is, individualsthat adjust their behaviour in response to the past behav-iour (or reputation) of their interaction partners. Thepresence of socially responsive individuals, in turn, canincrease both the degree of behavioural coordination andthe level of social competition within groups and

0169-5347/

� 2014 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.tree.2014.03.008

Corresponding author: Wolf, M. (m.wolf@igb-berlin.de).Keywords: individual differences; social responsiveness; coordination; social competi-tion; swarm intelligence; social network.

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populations. While a series of recent theoretical modelshas investigated this link between personality differences,social responsiveness and social functioning, to date littleis known about this relationship in natural systems. Wehere provide a brief summary of the main theoreticalpredictions.

One key prediction from a series of different models isthat, in a range of contexts including aggressive andcooperative interactions, the existence of personality dif-ferences selects for socially responsive individuals [2,3].The logic underlying this prediction is as follows. Whenchoosing an action, a socially responsive individual takesinto account the past behaviour (or reputation) of itsinteraction partners. Social responsiveness is thus pre-dicted to be particularly beneficial when (i) different inter-action partners differ in their behaviour, since this makesit beneficial to fine-tune the behaviour to particular inter-action partners and (ii) when such differences are consis-tent over time, since this allows a socially responsiveindividual to use past behaviour as a predictor for futurebehaviour.

The presence of socially responsive individuals, in turn,is predicted to increase the levels of behavioural coordina-tion within groups and populations, since socially respon-sive individuals match their behaviour to the behaviour oftheir interaction partners. In situations where individualswithin a group have the choice between taking the lead orfollowing, for example, the presence of socially responsiveindividuals can promote a high degree of coordinatedbehaviour among individuals within that group [4]. Inhawk-dove like contest situations, the presence of sociallyresponsive individuals can increase the frequency of ‘coor-dinated’ hawk-dove interactions, and decrease the frequen-cy of ‘uncoordinated’ hawk-hawk and dove-doveinteractions [2].

The presence of socially responsive individuals is alsopredicted to increase social competition within groups andpopulations. This is caused by the fact that socially respon-sive individuals might interrupt an interaction and look fora new interaction partner. This implicit threat inherent ininteractions with socially responsive individuals puts pres-sure on their interaction partners which, in turn, can giverise to social outcomes that differ substantially from thoseachieved in the absence of socially responsive individuals[3]. In the context of cooperation, for example, the presenceof socially responsive individuals can give rise to highlevels of cooperation in situations where very little cooper-ation is expected in the absence of socially responsiveindividuals [3].

Table 1. Three main ways how personality differences can affect social functioning and social structure at different levels of socialorganisation

Aspect Implications Refs

Social responsiveness,

behavioural coordination

and social competition

Personality differences select for socially responsive individuals. The presence of socially responsive

individuals, in turn, is predicted to

(i) increase the levels of behavioural coordination within groups and populations,

(ii) increase the social competition within groups and populations, thereby giving rise to social outcomes

(e.g., high levels of cooperation) that differ substantially from those achieved in the absence of socially

responsive individuals.

[2–4]

Problem-solving ability (i) ‘Pool of competence hypothesis’: the more diverse a group, the more likely it is to harbour the specialist

for any given problem.

(ii) Personality differences are associated with differences in experience, information acquisition and/or

information use. Such differences can promote the ability of groups to make use of swarm intelligence.

(iii) Personality differences can give rise to communication problems and in-group/out-group

categorization processes hampering group performance.

[6–8]

Social structure Personality types differ in the number and the frequency of interactions with others, the responsiveness to

previous social experiences and their preferred social interaction partners. As a consequence of these

differences, the composition of personality types within a group or population can have substantial

consequences for the emerging social fine structure.

[9–11]

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Problem-solving abilitySecondly, personality differences can be expected to affectthe problem-solving ability of groups. Different personalitytypes often differ in their relative ability to solve differentecological problems. In fish, birds and rodents, for example,proactive types tend to outperform reactive types understable environmental conditions, whereas reactive typesoutperform proactive types under changing environmentalconditions [5]. Analogous context-dependent differences inthe relative performance of personality types can beexpected to be present in many other contexts. Conse-quently, for any given ecological problem, the more diversea group, the higher its chance that it harbours the special-ist for that problem (‘pool of competence hypothesis’ [6]). Ifa group can capitalize on this pool of abilities (e.g., viasocial learning), more diverse groups should thus be betterproblem solvers than less diverse groups; first evidence inbirds is in line with this hypothesis [6].

The presence of personality differences might also affectthe ability of groups to develop swarm intelligence (akacollective intelligence and wisdom of the crowd). In brief,swarm intelligence occurs whenever for a given cognitiveproblem a group can outperform even the best of itsmembers [7]. Importantly, many of the mechanisms un-derlying swarm intelligence require that individuals differin their experience and/or in the way they acquire orevaluate information [7]. Put simply, whenever individualswithin a group are too similar, the swarm intelligencepotential is diminished. Personality differences can beexpected to be an important source of this required be-tween-individual variation, since different personalitytypes often differ systematically in experience, informationacquisition and information use [5]. The presence of differ-ent personality types within a group might thus be a keyfactor promoting the ability of that group to make use ofswarm intelligence. To the best of our knowledge, this linkbetween personality differences and swarm intelligenceremains largely unexplored in the animal literature.

Before moving on, we stress that the existence of person-ality differences might not only have positive effects on theproblem-solving ability of groups. In humans, for example,between-individual diversity can give rise to communicationproblems and in-group/out-group categorization processes,

hampering group performance [8]; similarly, between-indi-vidual diversity might weaken group cohesion in many non-human species, thereby decreasing performance in taskswhere cohesion is important.

Social structureThirdly, personality differences can be expected to be animportant factor underlying the emerging social fine struc-ture (i.e., social interaction network) within groups andpopulations. Personality types differ in the number andthe frequency of interactions with others, the responsive-ness to previous social experiences, and their preferredinteraction partners [1,5]. As a consequence, the composi-tion of personality types within a group or population can beexpected to be a key determinant of its emerging social finestructure. To date, few studies in the animal literature haveexplicitly addressed this potentially important relationshipbetween personality types and social fine structure.

In one of these studies, bold sticklebacks, Gasterosteusaculeatus, have been shown to have fewer interaction thantheir shy conspecifics, but to distribute these interactionsmore evenly across all group members [9]. Shy individuals,in contrast, associated preferentially with a small numberof other group members. As a result, groups composed ofbold individuals were characterized by a relatively lownumber of interactions and a uniform distribution of theseinteractions whereas groups of shy individuals were char-acterized by more long-lasting associations between indi-viduals and highly non-uniform interaction distributions.

Different personality types differ consistently in theirresponsiveness to previous social experiences. Whether ornot individuals in a group or population respond to previ-ous social experiences (e.g., via breaking interactions), andhow frequent such responsive individuals are, can havesubstantial consequences for social network dynamics andthe emerging social fine structure. For example, in anexperiment with humans, when given the chance to breakinteraction links, compared to a situation where individu-als could not break interaction links, highly clusterednetworks emerged which, in turn, promoted high levelsof cooperation [10].

Personality types might also differ in their preferredsocial interaction partners. Homophily, for example, refers

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to the observation that humans tend to associate withothers that are similar to themselves. Such systematicdifferences in partner preferences, in turn, can give riseto non-random mixing of individuals in social networks andassortment based on personality types, a phenomenon thathas been observed in a wild population of Trinidadianguppies, Poecilia reticulata [11].

To sum up, we have discussed three main ways in whichthe existence of personality differences can affect the socialfunctioning and the social structure of groups and popula-tions. While certainly not being comprehensive, the abovediscussion highlights the broad and significant conse-quences that personality differences can have for socialprocesses and we hope that our article serves as a startingpoint for a research focus that aims at a systematic under-standing of these consequences.

AcknowledgmentsWe thank Paul Craze and two anonymous reviewers for constructivecriticism and valuable comments, we also thank the participants of theSymposium ‘Personality: causes and consequences of consistent beha-vioural variation’ and the Volkswagen Foundation for funding thisSymposium. This work was part of the B-Types project funded throughthe Leibniz Competition (SAW-2013-IGB-2).

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