How eye movements affect unpleasant memories: Support for a working-memory account

Abstract

Eye movement desensitization and reprocessing can reduce ratings of the vividness and emotionality of unpleasant memories—hence it is commonly used to treat posttraumatic stress disorder. The present experiments compared three accounts of how eye movements produce these benefits. Participants rated unpleasant autobiographical memories before and after eye movements or an eyes stationary control condition. In Experiment 1, eye movements produced benefits only when memories were held in mind during the movements, and eye movements increased arousal, contrary to an investigatory-reflex account. In Experiment 2, horizontal and vertical eye movements produced equivalent benefits, contrary to an interhemispheric-communication account. In Experiment 3, two other distractor tasks (auditory shadowing, drawing) produced benefits that were negatively correlated with working-memory capacity. These findings support a working-memory account of the eye movement benefits in which the central executive is taxed when a person performs a distractor task while attempting to hold a memory in mind.

Introduction

Eye movement desensitization and reprocessing (EMDR) is a psychological treatment for posttraumatic stress disorder (PTSD), an anxiety disorder that can develop after exposure to events that evoke intense fear, horror, or helplessness (American Psychiatric Association, 2000). Since 1990, thousands of clinicians have been trained in the use of EMDR procedures (Cahill, Carrigan, & Frueh, 1999), and EMDR has become a more complex and integrative form of therapy (Shapiro (2001), Shapiro (2002)). The present work examined how one component of EMDR—eye movements—affects participants’ reactions to their memories of unpleasant events.

The current treatment manual for EMDR is Shapiro (2001). During EMDR, the therapist asks the client to hold a distressing memory in mind along with accompanying emotions and a negative cognition associated with the memory. The therapist concurrently provides some form of bilateral stimulation. Most commonly, horizontal eye movements are elicited by having the client follow a repetitive side-to-side motion of the therapist's index finger. A set of 20 or more eye movements is performed while the memory is held in mind. The client then reports current sensations, cognitions, and emotions. Sets are repeated until the client reports minimal distress associated with the memory. The therapist then guides the client to replace the negative cognition with a client-generated positive one. Alternate forms of bilateral stimulation such as vertical or diagonal eye movements (Shapiro, 2001), lightly tapping the client's hands (Shapiro, 2001), or auditory tones (EMDRIA, 2000; Servan-Schreiber, Schooler, Dew, Carter, & Bartone, 2006) can be used if horizontal eye movements are not effective.