Envy is one of the seven deadly sins. But according to a new theory, people with an envious personality are more common than those with optimistic, pessimistic and trusting personalities. This four-part personality model is a fresh take on Jungian "types", which pivot on a person's level of introversion or extroversion (extroverts are the majority). The test is simpler than the 16-personality-type Myers-Briggs test developed from Jungian theory.Spanish researchers conducted an experiment in which 541 volunteers were presented with social dilemmas and had to reach decisions on what to do, working in collaboration or conflict with others, taking into account their own personal interests and those of the collective.story_article_left1One of the authors, Professor Anxo Sánchez from the University Carlos III of Madrid, gave an example: "Two people can hunt deer together, but if they are alone, they can only hunt rabbits.The person belonging to the envious group will choose to hunt rabbits because he or she will be at least equal to the other hunter, or maybe even better; the optimist will choose to hunt deer because that is the best option for both hunters.The pessimist will go for rabbits because that way he or she is sure to catch something; and the hunter who belongs to the trusting group will automatically co-operate and choose deer."The volunteers participated in pairs which changed every time the game changed. "In this way, we obtained information about what people do in very different social situations," said Sánchez.Based on the findings, a computer algorithm classified people into these four groups:• ENVIOUS: Don't mind what they achieve as long as they're better than everyone else;• OPTIMISTS: Believe they and their partner will make the best choice for both of them;• PESSIMISTS: Select the option they see as the lesser of two evils; and• TRUSTING: Born collaborators who will always co-operate, not really minding if they win or lose.The results indicated that 30% of the volunteers fell into the envious group, 20% fell into each of the trusting, optimistic and pessimistic groups, and 10% resisted classification.Yamir Moreno from the University of Zaragoza, one of the three collaborators, said these types of studies improved existing theories of human behaviour."The results go against certain theories - the one which states that humans act purely rationally, for example. They should be taken into consideration in redesigning social and economic policies," he said.Is the spread of envy a good or bad thing for human development? Nelspruit psychologist Moses Mkhabela said: "When [patients] feel envy they tend to engage in activities to bring down the other person and might land themselves in trouble."For example, a person envious of another's car or house might go into debt by trying to live at the same standard."I find people living in urban areas are more tolerant of other people achieving and doing well. However, people from rural areas who are disadvantaged are more at risk of the element of envy," said Mkhabela."I see a competitive spirit among children, which is good if it motivates the child to try and achieve, but it is negative if it results in dirty tricks to sabotage others' success." Who is envious? sub_head_end• Students who use Facebook for "surveillance" - to compare their lifestyles and activities with those of their friends - are more prone to envy and depression than those who use it to connect, research at the University of Missouri showed.• A 2012 study by researchers from Spain, Argentina and the Netherlands distinguished between jealousy and envy: "Jealousy implies a loss, or threat of loss, due to interference from a rival ... Envy is a response to another person who has success, skills or qualities that one desires and lacks."• The immune systems of extroverts seem to be better primed to deal with infection than those of people with cautious/ conscientious personalities, research by UK and US universities has found.• "We can't, however, say which came first. Is this our biology (immune cell gene expression) determining our psychology, or is our psychology determining our biology?" said lead researcher Professor Kavita Vedhara...