260 Journal of Intellectual Disability Research VOLUME 40 PART 3 PP 260-274 JUNE 1996 Time-based lag sequential analysis and the functional assessment of challenging behaviour E. Emerson, D. Reeves, S. Thompson, D. Henderson, J. Robertson & D. Howard Hester Adrian Research Centre, University of Manchester, Manchester, England Abstract This paper describes the applicationof time-based lag sequential analysis to the functionalassessment of challenging behavioursshown by people with severe learningdisabilities. The potential uses of the approach are illustratedwith regards to identifying: (I) aspects of the stimuluscontrol ofchallenging behaviour; (2) antecedents to the occurrence of challenging behaviour; and (3) the environmental consequences of challenging behaviour.The uses and limitations ofthe approach are discussed. Introduction Recent developments have seen the (re)emergence of a 'functional' perspective in behavioural approaches to the treatment of challenging behaviours shown by people with severe learning disabilities (Carr et al. 1990; Mace et al. 1991; Emerson 1995). This approach suggests that intervention should be based upon the results of a prior assessment of the processes responsible for maintaining the individual's challenging behaviour. Two strands of research have highlighted the importance of the functional perspective. Firstly, numerous studies have demonstrated that particular Correspondence: Eric Emerson, Hester Adrian Research Centre, University of Manchester, Manchester MI3 9PL, England, © 1996 Blackwell Science Ltd forms of challenging behaviour (e.g. self-injury) may be maintained by a variety of behavioural processes, including socially mediated positive and negative reinforcement, and automatic or perceptual reinforcement (e.g. Mace et al. 1986; Derby et at. 1992; Iwata et al. 1994). Secondly, research has shown that the effectiveness of approaches to intervention which are not based on punishment are dependant upon matching their procedural form to the behaviour's function (e.g. Carr & Durand 1985; Iwata et al. 1994). However, research has also illustrated the potential complexity of such issues (Carr 1994; Horner 1994). Thus, for example: (1) particular forms of challenging behaviour shown by different individuals may be maintained by different behavioural processes (see above); (2) distinct forms of challenging behaviour shown by the same individual may be maintained by different behavioural processes (e.g. Sprague & Horner 1992; Derby et al. 1994). (3) behaviours may be multiply controlled in that they may be maintained by more than one process (e.g. Carr & Durand 1985; Smith et al. 1993; Day et al. 1994); (4) the processes maintaining challenging behaviours may vary across contexts (e.g. Haring & Kennedy 1990) and over time (e.g. Lerman et at. 1994); (5) other behavioural processes such as schedule-induction (Emerson & Howard 1992) and conditioned emotional responding (e.g. Romanczyk et al. 1992) may be implicated in the maintenance of challenging