Towards an improved measure of the Edinburgh Handedness Inventory: A one-factor congeneric measurement model using confirmatory factor analysis Milan Dragovic University of Western Australia, Perth, Australia The Edinburgh Handedness Inventory was administered to a sample of 203 mentally well adults drawn from the Western Australian Family Study of Schi- zophrenia 90 men and 113 woman). Confirmatory factor analysis demonstrated that seven out of ten original items of the Edinburgh Handedness Inventory were sufficienttoprovideaninternallyconsistentandvalidmeasureofhandpreference. Exclusion of three problematic items led to a more refined measurement of the latent construct of handedness. The rationale for exclusion was: 1) redundancy stemming from collinearity between writing and drawing, and 2) an unacceptably large measurement error associated with two of the items use of broom and opening a box-lid). The results suggest that this revision of the Edinburgh Hand- edness Inventory enhances its measurement properties. Assessmentofhandednessisastandardprocedureinanyinvestigationofhuman behavioural asymmetries and in many neuropsychological investigations. Numerous ``handedness questionnaires'' have been designed, all with the intentiontoquantifythedirectionanddegreeofhandedness.Amongstthem,two appear to be the most prominent in current research: the Edinburgh Handedness Inventory EHI), Oldfield 1971), and Annett's handedness questionnaire Annett, 1970). The EHI is by far the most commonly used of the two Bishop, 1996). Although the EHI is widely used, only a few studies have examined its psychometric properties. Bryden 1977) recommended that items that do not conform to the undimensional construct of handedness e.g., using a broom, LATERALITY, 2004, 9 4), 411±419 Address correspondence to Milan Dragovic, Centre for Clinical Research in Neuropsychiatry, Private Mail Bag No. 1, Claremont, WA 6010, Australia. Email: milan@ccrn.uwa.edu.au I would like to thank the following individuals, listed in alphabetical order, for their help in the preparation of this manuscript: Associate Professor Geoff Hammond, Professor Assen Jablensky, Professor Aleksandar Janca, Neil Preston, and Danny Rock. # 2004 Psychology Press Ltd http://www.tandf.co.uk/journals/pp/1357650X.html DOI:10.1080/13576500342000248