What Makes an Idea Big in Psychology?

We can all think of big ideas in the history of psychology that provoked tremendous excitement and generated abundant research for many years. But what makes an idea big? And what are the common features of the big ideas of the past 25 years in psychology? We examine these questions in this article, focusing on 5 ideas that have become big over the past 25 years. They show several common features, including rising citation levels each year for at least 10 years after publication; over 1000 citations per year by the 10 th year; and a total of at least 5000 citations by the 10 th year. We propose the addition of a 25-year Impact Factor, to identify ideas that become big and to recognize that one key feature of big ideas is that their citations per year continue to rise even 25 years after publication. We also ask who gets to have big ideas, locating the answers in a combination of national wealth, funding devoted to universities and research, and opportunities for talented young people to develop and express their abilities. Several suggestions for expanding access to these opportunities are presented.