Psychology 2012. Vol.3, No.1, 30-35 Published Online January 2012 in SciRes (http://www.SciRP.org/journal/psych) http://dx.doi.org/10.4236/psych.2012.31005 Copyright © 2012 SciRes. 30 Pre-Schoolers’ Reports of Conflicting Points Secretly Inserted into a Co-Witnessed Event: An Experimental Investigation Using the MORI Technique Kazuo Mori 1 , Ryuta Takahashi 2 1 Institute of Engineering, Tokyo University of Agriculture and Technology, Tokyo, Japan 2 Osaka Family Court, Sakai, Japan Email: kaz-mori@cc.tuat.ac.jp Received November 5 th , 2011; revised December 6 th , 2011; accepted December 31 st , 2011 Thirteen pre-school and ten undergraduate pairs participated as eyewitnesses to a simulated criminal event presented through animated cartoons using a presentation trick (MORI technique). Although there were two different versions, the MORI technique had participants observe only one version without being aware of the other. In three reporting sessions, participants recalled what they presumed they had jointly observed; individually immediately after the presentation, collaboratively after the individual recall, and again individually one week later. The main results were: pre-schoolers, as well as undergraduates, showed better recall in the collaborative tests, though the former generally showed poorer recall than the latter, pre-schoolers tended to conform more frequently than undergraduates in the week-later tests, and both pre-school and undergraduate pairs conformed more often for amendment than distortion. Keywords: Eyewitness Testimony; Pre-School Child Pairs; MORI Technique; Conformity Introduction There are various reasons for the bias of information in wit- ness testimony, but that of co-witnesses has been reported to be crucially influential (Kanematsu, Mori, & Mori, 1996/2003; Gabbert, Memon, & Allan, 2003; for a recent review, see Wright, Memon, Skagerberg, & Gabbert, 2009). In Kanematsu, et al. (1996/2003), co-witness pairs observed the same event, but with hidden discrepancies secretly inserted using a presen- tation trick (the MORI technique, Mori, 2003). Researchers found that, in subsequent discussion of what they had witnessed together, participants tended to modify their own memory of what they had observed in order to conform to that of their co-witnesses. Mori and his collaborators have conducted a se- ries of experiments to investigate the memory distortions of co-witnesses under various conditions: male vs. female pairs (Matsuno, Mori, Hirokawa, & Ukita, 2005), couples vs. unac- quainted pairs (French, Garry, & Mori, 2008), one-vs-two wit- nesses and two-vs-two witnesses (Mori & Mori, 2008), as well as mother-child pairs (Mori & Kitabayashi, 2009). Gabbert, Memon, and Allan (2003) also investigated the co-witness effect on memory recollection utilizing a different paradigm. They showed pairs of participants a simulated criminal event videotaped from two different angles such that each participant viewed one of the two video versions which included some details that were not visible in the other and vice versa. They found a significant proportion (71%) of participants who had discussed the event recalled details that had been ac- quired during the discussion rather than through direct observa- tion. Co-witness conformity research utilizing the Gabbert method (Gabbert, et al., 2003), in which the co-witness pairs observed a slightly different version of an event separately, and that utiliz- ing the MORI technique, in which the co-witness pairs ob- served the same event together without being aware of the du- ality, showed similar research findings. As stated above, fun- damentally both sets of studies revealed that the recollections of independent witnesses tend to be strongly influenced by those of their co-witnesses. Recently, Gabbert, Memon, and Wright (2007) found that participants/witnesses who believed their partners had observed the event longer tended to conform to them. French, Garry, and Mori (2011) found similar results with the Mori method. They manipulated participants’ expectations by leading them to be- lieve that they had either “higher or lower visual acuity” than their partners when together they watched a video event in which several discrepancies had been inserted secretly. The results showed that, although the actual visual acuity was equal in reality, participants who believed that they had “lower visual acuity” conformed more than their counterparts with “higher visual acuity.” It is noteworthy that these two studies independently re- vealed the same fact, that co-witnesses tended to take their partners’ credibility into account when deciding whether they would conform to them or not. The co-witness conformity ef- fects are crucial in the application of research results to actual investigation and judicial practices. Therefore, it is worth em- phasizing that the same research findings need to be corrobo- rated by various independent researchers using different ex- perimental methods. Relatively few experimental studies have been done on co-witness effects in children. Child witness testimony has been a major research topic in applied cognitive and forensic psy- chology. Child witnesses have been studied because they are often the victims in child abuse cases, and the credibility of their memory and overall cognitive ability is a major concern in