London, Sep 18: People can be classified into four basic personality types: optimistic, pessimistic, trusting and envious, a new study on human behaviour has found.

Envious, is the most common, with 30 percent compared to 20 percent for each of the other three groups, researchers said. The study, including researchers from Universidad Carlos III de Madrid in Spain, analysed the responses of 541 volunteers to hundreds of social dilemmas, with options leading to collaboration or conflict with others, based on individual or collective interests.

Those involved are asked to participate in pairs, these pairs change, not only in each round, but also each time the game changes, said Anxo Sanchez, one of the authors of the study.

So, the best option could be to cooperate or, on the other hand, to oppose or betray. In this way, we can obtain information about what people do in very different social situations, said Sanchez.

The results go against certain theories; the one which states that humans act purely rationally for example, and, therefore, they should be taken into consideration in redesigning social and economic policies, as well as those involved in cooperation, said Yamir Moreno, from Universidad de Zaragoza in Spain.

After carrying out this kind of social experiment, the researchers developed a computer algorithm which set out to classify people according to their behaviour. The algorithm organised 90 percent of people into four groups: the largest group, accounting for 30 percent, being the envious - those who don’t actually mind what they achieve, as long as they’re better than everyone else; the optimists - who believe that they and their partner will make the best choice for both of them - on 20 percent.

Also on 20 percent were the pessimists - who select the option which they see as the lesser of two evils - and the trusting group - who are born collaborators and who will always cooperate and who do not really mind if they win or lose.

There is a fifth, undefined group, representing 10 percent, which the algorithm is unable to classify in relation to a clear type of behaviour, researchers said. They noted that this allows them to infer the existence of a wide range of subgroups made up of individuals who do not respond in a determined way to any of the outlined models. The study was published in the journal Science Advances.

--PTI