Specialization versus diversification in research activities: the extent, intensity and relatedness of field diversification by individual scientists

We investigate whether and in what measure scientists tend to diversify their research activity, and if this tendency varies according to their belonging to different disciplinary areas. We analyze the nature of research diversification along three dimensions: extent of diversification, intensity of diversification, and degree of relatedness of topics in which researchers diversifies. For this purpose we propose three bibliometric indicators, based on the disciplinary placement of scientific output of individual scientists. The empirical investigation shows that the extent of diversification is lowest for scientists in Mathematics and highest in Chemistry; intensity of diversification is lowest in Earth sciences and highest in Industrial and information engineering; and degree of relatedness is lowest in Earth sciences and highest in Chemistry.