Fast track report Further validation of a single-item measure of social identification STEPHEN REYSEN 1 *, IVA KATZARSKA-MILLER 2 , SUNDÉ M. NESBIT 3 AND LINDSEY PIERCE 1 1 Texas A&M University–Commerce, Commerce, USA; 2 Transylvania University, Lexington, USA; 3 University of Northern Iowa, Cedar Falls, USA Abstract We examine the validity and reliability of a single-item measure of social identification (SISI). Convergent validity is shown with significant positive correlations with previously published unidimensional and multidimensional measures of in-group identification and other group-relevant measures (e.g., entitativity and collective self-esteem). Divergent validity is shown via nonsignificant correlations with social desirability measures. Predictive validity is shown with positive correlations with group-relevant behavior (e.g., volunteerism and voting). External validity is shown with correlations with other in-group identification measures in a community sample. The reliability of the scale is shown by examining scores of the SISI for six different identities at three points in time. Copyright © 2013 John Wiley & Sons, Ltd. Since their publication, social identity theory (Tajfel, 1978; Tajfel & Turner, 1979) and later the theoretical expansion of self-categorization (Turner, Hogg, Oakes, Reicher, & Wetherell, 1987) have steadily and increasingly impacted the field of psychology (Postmes & Branscombe, 2010). A key conceptual advancement of social identity theory is the notion that individuals categorize themselves into specific social iden- tities, resulting in the tendency to behave as a collective group, as opposed to individuals. Since the seminal Tajfel and Turner (1979) publication, researchers have proposed a multitude of terms, operationalizations, and measures to define and assess the strength of connection between the individual and the group. For example, in-group identification has been defined and operationalized as liking for the group (Brewer, 1991; Hornsey & Hogg, 2000), group pride (Smith & Tyler, 1997), attraction to the group (Jackson & Smith, 1999), degree of self-definition (Turner et al., 1987), attachment (Smith, Murphy, & Coats, 1999), importance of the group for self- image (Luhthanen & Crocker, 1992), congruence of self and group values (Pratt, 1998), perception of belongingness (Dutton, Dukerich, & Harquail, 1994), sense of oneness with the group (Mael & Tetrick, 1992), sense of closeness (Canover & Feldman, 1984), and the extent to which the group is incor- porated into the self (Tropp & Wright, 2001). The vast array of definitions and operationalizations has led to a wealth of mea- sures (unidimensional and multidimensional) that are currently used to assess in-group identification. As social identity researchers explore applications of this theory in community samples using longitudinal designs (e.g., Haslam, Jetten, Postmes, & Haslam, 2009), the need has arisen for a short, reliable, and valid measure of in-group identification. Single-item scales are advantageous for researchers who conduct large-scale surveys or those who conduct research in contexts where time or space is limited. The use of a single item can help to reduce the time for data collection, participant fatigue, and the data-processing costs associated with large-scale research (for a review of the advantages and disadvantages of single-item measures, see Bergkvist & Rossiter, 2007). Although multi-item measures are generally more preferable than single-item scales, it is unclear as to whether a single-item measure can provide a valid and reliable assessment in certain research contexts (e.g., measuring identification with multiple groups in the same study) and be a good alternative method for measuring social identification among groups. The present set of studies examined the validity and reliability of a slightly modified version of Postmes, Haslam, and Jans’ (2012) single-item measure of social identification (SISI). In the present studies, the SISI, “I identify with my [insert group],” was revised to read “I strongly identify with [insert group].” In Study 1, we administered the SISI with previously published in-group identification measures and group-relevant scales to examine convergent validity. In Study 2, we administered the SISI, previously published in-group identification scales and group-relevant scales (convergent validity), behavioral measures (predictive validity), and social desirability scales (divergent validity). In Study 3, we administered the SISI and previously published in-group identification scales to a noncollege sample of adults (external validity). In Study 4, we assessed participants’ ratings on the SISI across a semester to examine SISI’s reliabil- ity. Across these studies, we argued that the SISI is a reliable and valid measure of in-group identification. *Correspondence to: Stephen Reysen, Department of Psychology, Texas A&M University–Commerce, Commerce, TX 75429, USA. E-mail: Stephen.Reysen@tamuc.edu European Journal of Social Psychology, Eur. J. Soc. Psychol. 43, 463–470 (2013) Published online 5 August 2013 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/ejsp.1973 Copyright © 2013 John Wiley & Sons, Ltd. Received 18 March 2013, Accepted 23 June 2013