Review Rituals, stereotypy and compulsive behavior in animals and humans David Eilam a, * , Rama Zor a , Henry Szechtman b , Haggai Hermesh c a Department of Zoology, Tel-Aviv University, Ramat-Aviv 69978, Israel b Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ont., Canada L8N 3Z5 c Outpatient Department and Anxiety Disorders and Behaviour Therapy Unit, Geha Mental Health Center, Rabin Medical Center, Beilinson Campus, Petach-Tiquva 49 100 and Sackler Faculty of Medicine, Tel Aviv University, Ramat-Aviv, Israel Received 29 May 2005; revised 19 July 2005; accepted 24 August 2005 Abstract From a survey of the behavior of animals in the wild, in captivity, under the influence of psychoactive drugs and in a model of obsessive- compulsive disorder (OCD), we identify that the behavioral repertoire invariably includes motor rituals, and that such rituals are performed at a few specific locations/objects in the environment with an orderly transition amongst locations/objects. The concept and parameters of this stable organization of rituals in time and space were used to analyze rituals of OCD patients, compared with control individuals performing the same actions (e.g. car locking). It was found that human rituals also converged to a few places/objects where repetitive acts were performed in a regular order, with the acts in OCD patients overlapping with those of control individuals. Across a very diverse range of animals and conditions, motor rituals are thus characterized by their close linkage to a few environmental locations and the repeated performance of relatively few acts. Such similarity in form may reflect a similarity in the mechanisms that control motor rituals in both animals and humans. q 2005 Elsevier Ltd. All rights reserved. Keywords: Obsessive-compulsive disorder; Pacing; Stationary; Quinpirole; Amphetamine; Route stereotypy; Focused stereotypy; Spatiotemporal structure Contents 1. Prolog ........................................................................................ 456 1.1. Repetitive motor rituals: Form and function in normal behavior of animals and humans ....................... 457 1.2. Rituals in cage and drug stereotypies ............................................................. 459 1.3. Ethological study of rituals in OCD patients ....................................................... 465 1.3.1. The building blocks of malfunctional compulsive rituals ........................................ 465 1.3.2. The repetitive structure of rituals in OCD patients ............................................. 465 1.3.3. Quantifying different rituals of different patients .............................................. 467 2. Epilogue ....................................................................................... 467 Acknowledgements ............................................................................... 469 References ..................................................................................... 469 1. Prolog Obsessive-Compulsive Disorder (OCD) is a severe, chronic psychiatric problem. It was recognized as early as the 16th century, and is now known to have a prevalence rate of 1–3%, which is almost twice that of schizophrenia (Karno et al., 1988; Weissman et al., 1994). Obsessions refer to recurring, persistent thoughts, impulses or images that inappropriately intrude into awareness and cause marked distress or anxiety. Compulsions are the need to repeat physical behaviors such as checking or mental behaviors such as counting things, and occur as a response to an obsession or in accordance with strictly applied rules (DSM-IV; APA, 2000). The most common form of OCD behavior is that of compulsive checking (Henderson and Pollard, 1988; Rasmussen and Eisen, 1992), which may be performed for hours and in extreme cases may prevent the subject from sleeping or leaving home. Despite their understanding that their obsessive-compulsive behaviors Neuroscience and Biobehavioral Reviews 30 (2006) 456–471 www.elsevier.com/locate/neubiorev 0149-7634/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.neubiorev.2005.08.003 * Corresponding author. Tel.: C972 3 6406471; fax: C972 3 6409403. E-mail address: eilam@post.tau.ac.il (D. Eilam).