SPECIAL ISSUE PAPER Patterns of Interobserver Error in the Scoring of Entheseal Changes C. B. DAVIS, a K. A. SHULER, b M. E. DANFORTH a * AND K. E. HERNDON b a Department of Anthropology and Sociology, University of Southern Mississippi, Hattiesburg, MS, USA b Department of Sociology, Anthropology and Social Work, Auburn University, Auburn, AL, USA ABSTRACT Although the interpretation of entheses has undergone considerable discussion recently, the role of interobserver error, especially in comparative contexts, has been only sporadically addressed. Using standards developed by Hawkey and Merbs, currently the most widely used system, rates of reproducibility were evaluated in two prehis- toric North American skeletal series. Eight observers of varying experience levels scored 17 long bone entheses, representing both fibrous and fibrocartilaginous attachment types, on 58 individuals. Results showed rates of re- producibility to be only marginally higher than what would be expected by chance alone. Observer experience level did not appear to be a factor nor was attachment type. As might be predicted, those entheses enjoying the highest rates of reproducibility exhibited relatively smooth attachment morphology and/or less defined boundaries whereas those with the lowest rates displayed the greatest range of surface morphology expression. Possible explanations for the levels of interobserver error observed include difficulties in reducing the highly variable enthesis morphology to a few discrete categories, categories that encompass too many criteria, and use of vague terminology in describing morphological features. Consequently, comparison of data across studies by different observers, especially those not trained by the developer of a given scoring method, must be undertaken with great caution. Copyright © 2012 John Wiley & Sons, Ltd. Key words: entheses; entheseal changes; interobserver error; musculoskeletal markers; reconstruction of activity; reproducibility; scoring methods Introduction The number of bioarchaeological investigations using the morphology of muscle attachment sites to reconstruct past activity patterns has increased dramatically in recent years, but there is growing concern as to their true eti- ology (e.g. Jurmain et al., 2012; Meyer et al., 2011). The most commonly used term for this skeletal indicator is musculoskeletal markers (e.g. Hawkey & Merbs, 1995; Weiss et al., 2012), thereby implying a causal relationship between enthesis expression and the amount of time and intensity of stress placed by the muscle or tendon on the bone. Recently, however, this correlation has been challenged; age, sex, body size, and possibly genetics have also been found to influence attachment site formation (Alves Cardoso & Henderson, 2010; Villotte et al., 2010a; Weiss, 2003; Weiss et al., 2012). Still other researchers have suggested that the marker be called enthesopathies, even though normal muscle attachment morphology is at times encompassed by the term (Jurmain & Villotte, 2010). Given all of these concerns, Jurmain & Villotte (2010) have recommended the label of entheseal changes with its more neutral connotations be used. Although the roles of various contributory factors in entheseal changes have been explored, less attention has been given to the role of the standards used in scoring entheses when making interpretations. Muscle attach- ment site morphology can be unique and highly com- plex, but most scoring systems reduce this variability into a limited number of expression categories. Integrat- ing archaeological, ethnographic, sports medicine, and electromyographic analysis, Hawkey & Merbs (1995) developed the first widely applied scoring system for entheseal changes, and it still remains the most commonly used in bioarchaeological studies in the United States. Their method includes a visual reference system com- prised of three scoring variables: (i) Robusticity, which is * Correspondence to: Marie Elaine Danforth, Department of Anthropol- ogy and Sociology, University of Southern Mississippi, Hattiesburg, MS 39406-0001, USA. e-mail: m.danforth@usm.edu Copyright © 2012 John Wiley & Sons, Ltd. Received 31 July 2012 Revised 7 September 2012 Accepted 13 September 2012 International Journal of Osteoarchaeology Int. J. Osteoarchaeol. 23: 147–151 (2013) Published online 24 October 2012 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/oa.2277