The first evidence to suggest a link was found by psychologists at the University of Exeter and the University of Amsterdam.
Professor Alex Haslam and Dr Bertjan Doosje looked at patterns of voting in the contest between 1991 and 1996, before phone voting was allowed.
They found that juries from each country appeared to engage in a tit-for-tat strategy, awarding more points to nations that had previously favoured their songs.
Their study, published yesterday in the Journal of Applied Social Psychology, involved statistical analysis - and revealed the existence of “discrete voting cliques”, which acted to maintain patterns of mutual favouritism.
Prof Haslam and Dr Doosje found three main voting blocs.
Britain, Sweden, Iceland, Austria and Ireland made up one group. Finland, France, the Netherlands, Portugal and Switzerland formed another.
In the third group, Ireland made a second appearance along with Turkey, Bosnia-Herzegovina, Spain and Croatia.