Special issue preamble: Digit ratio (2D:4D) and individual differences research

The sexually differentiated second-to-fourth digit ratio (2D:4D) is currently frequently utilized in individual differences research as a putative indicator of the masculinizing brain organization effects of prenatal testosterone. This preamble introduces the journal special issue on this theme, entitled Digit ratio (2D:4D) and individual differences research. Notes regarding the background, history, and recent progress of 2D:4D research are provided, and the background of the special issue and the contents of its 11 research articles are briefly summarized. (C) 2011 Elsevier Ltd. All rights reserved.