Two people can learn to co-operate with each other intuitively, without communication or any conscious intention to co-operate, says a new study.
However, the process breaks down in the group of three or more, says the research.
The members of University of Leicester's School of Psychology and Department of Economics undertook the study to explain how two people learn to cooperate without even knowing that they are interacting with each other and in larger groups, explicit communication is needed to coordinate actions.
The researchers conducted a series of laboratory experiments with groups of various sizes and developed a mathematical model of the intuitive learning process.
Experimental participants received financial gains or losses after pressing one of two buttons on a computer, unaware that the outcome depended not on their own choice but on their neighbor's.
It turned out that after many repetitions of the game, gains gradually exceeded losses in groups of two but not in three-person and larger groups.
"In the game of life, while two people may 'develop an understanding' or work intuitively together - this scenario is easily distorted once a third person becomes involved. Without effective planning and ground rules, even the best of working relationships between two people can become undone once a third is involved," said Professor Andrew Coleman.
"Married couples or pairs of business partners may be able to rely on this type of intuitive cooperation, to an extent, but larger groups need explicit communication and planning. Mechanisms need to be put in place to facilitate it. Intuitive cooperation is really a case of two's company, but three's a crowd," he concluded.
The study is due to publish in journal Cognitive Psychology.