Digital Filtering: Background and Tutorial for Psychophysiologists


  • The authors wish to thank Jean M. Anhalt, Lawrence A. Farwell, Gabricle Gratton, Blair D. Hicks, Stephen W. Porges, David L. Roth, and Daniel S. Ruchkin for comments on earlier drafts of this paper. Steve Porges and Evan Byrne provided coefficients for the moving polynormal filters. We would also like to thank Bruce C. Wheeler for consultation on the electrical engineering litcrature Preparation of this paper was supported in part by National Institute of Mental Health grant MH39628.

Address requests for reprints to: Edwin W. Cook III, Department of Psychology, University of Alabama at Birmingham, Birmingham, AL 35294; or Gregory A. Miller, Department of Psychology, University of Illinois, 603 E. Daniel Street. Champaign. IL 61820.


Digital filtering offers more to psychophysiologists than is commonly appreciated. An introduction is offered here to foster the explicit design and use of digital filters. Because of considerable confusion in the literature about terminology important to both analog and digital filtering, basic concepts are reviewed and clarified. Because some time series concepts are fundamental to digital filtering, these are also presented. Examples of filters commonly used in psychophysiology are given, and procedures are presented for the design and use of one type of digital filter. Properties of some types of digital filters are described, and the relative advantages of simple analog and digital filters are discussed.