Approach–avoidance and happiness indicators in natural environments: a preliminary analysis of the Stimulus Preference Coding System Ashley J. Smith a , Elson M. Bihm b, * , Poonam Tavkar c , Peter Sturmey d a 238 Burnett Hall, Department of Psychology, University of Nebraska-Lincoln, Lincoln, NE 6 8588 0308, USA. b Department of Psychology and Counseling, 201 S. Donaghey, University of Central Arkansas, Conway, AR 72035-0001, USA c Queens College, City University of New York, USA d Queens College and the Graduate Center, City University of New York, USA Received 12 November 2003; received in revised form 9 March 2004; accepted 21 June 2004 Abstract Two studies assessed the reliability and utility of the Stimulus Preference Coding System (SPCS) to measure approach, avoidance, and happy and unhappy behaviors in persons with developmental disorders. Study 1 took place in an institutional setting. The nine participants were all adults with mental retardation and multiple associated disabilities. Inter-observer reliability ranged from 72% to 100%. Study 2 took place in an after-school setting. The four participants were children diagnosed with autism and mental retardation. Inter-observer agreement ranged from 70% to 91%. Approach and avoidance behaviors were a function of staff person and task. The SPCS may be useful in identifying reinforcers, promoting happiness, analyzing task and staff effects, and clarifying the relationship of stimulus preference to psychopathology. # 2004 Elsevier Ltd. All rights reserved. Keywords: Psychopathology; Inter-observer agreement; Stimulus preference Research in Developmental Disabilities 26 (2005) 297–313 * Corresponding author. Tel.: +1 501 450 5417. E-mail address: elsonb@uca.edu (E.M. Bihm). 0891-4222/$ – see front matter # 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.ridd.2004.06.001