Eyewitnesses’ memories conform to each other following discussion 目撃者の記憶の話し合いによる同調 Lauren French1, Toni Kinzett1, Kazuo Mori2 & Maryanne Garry1
Paterson & Kemp 86% of witnesses said they discussed a significant event with a co-witness. 目撃者の86% が互いに話し合うと答えた
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Why is it important? なぜ重要なのか？ Justice system 司法判断 Criminal liability 賠償責任 Insurance 保険請求
Research question ｰ研究目的 What happens when people discuss an event that they remember differently? 目撃記憶に違いがあったとき 話し合いは何をもたらすか？
What we did… Takarangi et al (in press) ｰTakarangiらが作成した映像 Two versions of one movie 同じ出来事に２つの映像 Electrician working in a house 電気修理屋さんが留守宅に訪問 Eight critical items ８カ所に違い
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MORI Technique Polarizing glasses Polarizing filters Viewer A Viewer B Rear projection screen Stacked projectors (each attached to a separate computer) Polarizing filters Polarizing glasses Viewer A Viewer B
Equipment
Equipment
Cover storyｰ眼鏡をかける理由 “We are interested in people’s sensory impressions at different levels of visual acuity… you will be in the 95% acuity condition and will wear 95% acuity glasses…” “視界の明瞭さの影響を研究している ので、明瞭さが95%になるサングラスをかけてもらう。”
Procedureｰ手続き N = 40 (20 pairs) Version 1 Version 2 Discussion 15 min
Discussionｰ話し合い Shown 12 questions to talk about 12の質問について話し合わせる Displayed on rear projection screen リヤスクリーンに質問を提示 4 related to critical items ４問は食い違い項目 Other 4 critical items acted as control 話し合わない４項目と比較する
In the lounge, Eric looked at a picture of _______ エリックが 居間で見た絵は？ The Leaning Tower The Tower of London The Eiffel Tower The Sky Tower Trump Towers ピサの斜塔 ロンドン塔 エッフェル塔 スカイタワー トランプタワー
In the lounge, Eric looked at a picture of _______ The Leaning Tower The Tower of London The Eiffel Tower The Sky Tower Trump Towers
Procedureｰ手続き N = 40 (20 pairs) 3 min 15 min Version 1 Discussion Recognition test 再認テスト 15 min 3 min
Recognition testｰ再認テスト 20 two-alternative forced-choice items ２肢選択20問 8 related to critical details うち８問が食い違い項目 設問ごとに自信度評定
Memory for Discussed Items ｰ話し合いの効果 正答数（全４問） Correct Response (out of 4) 話し合わなかった項目 Discussed vs Non discussed items 話し合った項目 Not Discussed Discussed t(39) = 4.97, p < .01
Opportunity to conform ｰ同調の機会 Not mentioned Mentioned 見ていない情報への言及あり 見ていない情報への言及なし Percentage of discussions where misinformation was mentioned
Opportunity to conform ｰ同調の機会 Not mentioned Ignored Conformed 言及された見ていない情報に同調 見ていない情報への言及なし 言及された見ていない情報を無視 Percentage of times misinformation was mentioned and later ignored or conformed with.
Confidence: Overall ｰ自信度：全体 Overall Confidence (scale 1 - 5) 話し合わなかった項目 話し合った項目 Not Discussed Discussed t(39) = 0.30, p = 0.76
Confidence: True Vs. False Memories ｰ自信度と記憶の正確さ Overall Confidence (scale 1 - 5) 正しい 記憶項目 間違った記憶項目 True memories False memories t(39) = 3.59, p < .01
Agreed with misinformation during discussion Influence of prior agreementｰ話し合いでの同意の影響 Normative Influence 規範の影響(社会的な同意 ) 正 誤 Informational Influence 情報の影響（情報に同意） 話し合い時に誤情報に同意していた場合 Check labels Agreed with misinformation during discussion Correct Misled
Influence of prior agreement ｰ話し合い時の同意の影響 Correct：正答 Misled：誤答 Did not agree with misinformation during discussion 話し合い時に誤情報に同意しなかった場合 誤答 誤答 話し合い時に誤情報に同意していた場合 Agreed with misinformation during discussion
Summary ｰまとめ People added parts of others’ recall into their own memory reports, even when that information contradicted what they actually saw. 自分が実際に見た情報と食い違う場合でさえ、他人の再生情報を自分の記憶として報告することがある。
Summary ｰまとめ 67% of the times that people were exposed to misinformation they used it in their later memory report. 話し合い時に示された誤情報の 67%を自分の記憶として報告した。
Summary ｰまとめ People were more likely to use misinformation as an answer if they previously agreed to it during discussion. 話し合い時に同意した誤情報はその後の報告でもそのまま使われやすい。
Conclusion ｰ結論 It is unwise for witnesses to talk to each other about what they have seen. 目撃者同士で話し合いをさせるのは避けるべきである。 The MORI technique provides an excellent way to research eyewitness discussions and memory. MORIテクニックは目撃者間の話し合いと記憶についての優れた研究手法である。
Implications ｰ提言 In real life, witnesses may add completely false details into their memory reports of a crime. 現実社会でも、目撃者が犯罪の目撃証言に間違 った事実を述べているかもしれない。
Implications ｰ提言 Witnesses should be discouraged from talking to each other. 目撃者同士で話し合いをしないような措置をとる べきだ。
Implications ｰ提言 When witnesses have had the opportunity to discuss an event, matching testimony should not be taken to be corroborating evidence. 目撃者同士での話し合いがなされているならば、証言に 一致が見られてもそれが証拠をより確かなものにしてい ると考えてはならない。
Thanks Kaz! Put photo of Kaz This research was supported by a Grant-in-Aid from the Japanese Ministry of Education, Culture, Sports, Science, and Technology (Grant No.16330139) to KM. LF is supported by a Victoria University Postgraduate scholarship.