Multidimensional scaling and the analysis of sexual offence behaviour: a reply to Sturidsson et al.

Abstract

Sturidsson et al. (Psychology, Crime & Law, 12, 221–230, 2006) published an article on the replicability of early multidimensional scaling (MDS) behavioural research by Canter and Heritage (Journal of Forensic Psychiatry, 1, 185–212, 1990). Sturidsson et al. were unable to find a ‘readily apparent, simple interpretation’ of their MDS solution and therefore suggested that the MDS approach may be flawed as a device for interpreting sexual assault. The current paper explains how the methods employed by Sturidsson et al. represent an incorrect use of MDS, specifically in their input of Jaccard similarity data into the MDS (ALSCAL) procedure in SPSS as opposed to the correct MDS (PROXSCAL) procedure. A comparative example is used to illustrate how adopting the ALSCAL procedure will result in an inverse MDS solution, where objects appearing closer together are more dissimilar, making interpretation of the MDS plot meaningless in this context. The current paper discusses this methodological flaw in greater depth and in the context of behavioural investigative research using MDS in general. It concludes with some general guidelines in utilizing the MDS procedure in SPSS specific to criminal profiling research.