Prejudice: Ageism is the most prevalent form of prejudice in the UK, and religious segregation in Northern Ireland is getting worse, the BA Festival of Science was told.
Experts said prejudice affected many groups in society, and social psychologists had a crucial role in resolving this problem.
Some 43 per cent of people in the UK reported experiencing some form of prejudice, said Prof Dominic Abrams from the University of Kent.
His survey showed that 65 per cent of these reported suffering ageism, which made it as frequent as women's experience of sexism.
"We need scientists who are engaged in real-life social problems spread across the globe," said Prof Miles Hewstone of the University of Oxford and president of the BA psychology section.
"We need top-flight theories backed with the best we've got in modern methods to try to work out the best interventions to reduce prejudice."
The first national survey of ageism in Britain revealed its pervasive nature, according to Prof Abrams. Some 50 per cent of people believed they were written off as "old" once they reached 50.
Many stereotypes of elderly people were apparent, and people generally believed that "more youthful is more useful", he said. "People of all ages think people over 70 are regarded as friendlier but less capable than those under 30."
Prof Abrams said the age at which people were perceived as old was complex.
"On average, people stated that youth ends at 49 and old age begins at 65, but these ages increase as people get older.
"If you are a 24-year-old man you believe that old age begins at 55, which is interesting because if you are a 62-year-old woman you believe that youth doesn't end until you are 57. "Age is in the eye of the beholder, but ageism is ubiquitous."
Prejudice in Northern Ireland was also addressed at the festival by Prof Ed Cairns from the University of Ulster. He suggested that many people in the North spoke of the "peace-fire" as a reflection of their belief that the ceasefire was being maintained by military groups instead of good will.
"Politicians, law-makers and economists have had a crack at the peace process, but the acts of violence are still occurring."
Prof Cairns undertook the first scientific study of intergroup contact in the North.
His research revealed that intergroup contact works best when the groups are clear that they are interacting with members of the "other community".
He said this was when "intergroup anxiety" was more likely to be dissipated.
This form of anxiety stemmed from the expectations of negative consequences for oneself during interactions, such as embarrassment or discrimination.
Dr Vikki Burns is a research scientist at the University of Birmingham and is on placement at The Irish Times as a media fellow for the British Association for the Advancement of Science