1. The problems with linguistic credibility assessment of children Megan P. Y. Sim, Michael E. Lamb University of Cambridge 4th Annual iIIRG conference June 2, 2011

2. Police interviewing and interrogations • Procedure • Where does credibility assessment play a role?

3. Credibility assessment • Criteria-based content analysis (CBCA) • Reality monitoring (RM) • Behaviour analysis interview (BAI) • Linguistic inquiry word count (LIWC)

4. Linguistic Inquiry Word Count • LIWC & children’s statements • Children’s credible and doubtful statements • Children’s truthful and untruthful accounts of bullying • Children’s mock courtroom testimony

5. LIWC and children - summary

6. Present study goals • Using LIWC to study children’s statements • Understand children’s normative linguistic styles • Motivational factors

7. Research questions • Do motivational factors affect linguistic aspects of children’s disclosure? • How do these motivational factors affect children’s accounts?

8. Method • Cases • 97 interviews with alleged victims conducted by police officers in Britain (Lamb et al., 2009) • Age: 4 to 13 years (M = 9.3, SD = 2.58)

9. Method • Transcript preparation • Accurate transcripts • Identifying information deleted • Further modifications according to LIWC manual • Substantive portion of interview • Child’s statements

10. Motivational factors • Age • Gender • Relationship to suspect • Abuse type • Number of incidents of abuse • Interview type

11. Analyses • Analyses focused on group differences in factors that might affect children’s motivation and cooperation • Age group • Gender • Relationship to suspect • Abuse type • Number of incidents • Interview type

12. Analyses • Examined the children’s use of • First-person singular pronouns • Third-person pronouns • Affective processes • Negative emotion words • Exclusive words • Perceptual processes • Feel words • Motion words • Space words • Time words • Insight • Total word count

13. Analyses • Examined the children’s use of • First-person singular pronouns • Third-person pronouns • Affective processes • Negative emotion words • Exclusive words • Perceptual processes • Feel words • Motion words • Space words • Time words • Insight • Total word count

14. Analyses • Examined the children’s use of • First-person singular pronouns • Third-person pronouns • Affective processes • Negative emotion words • Exclusive words • Perceptual processes • Feel words • Motion words • Space words • Time words • Insight words • Total word count

15. Research questions • Do motivational factors affect linguistic aspects of children’s disclosure? • How do these motivational factors affect children’s accounts?

16. Results – Age effects • Total word count χ2(2) = 24.87, p < .001 • Exclusive words F(2, 94) = 7.36, p = .001, ω2 = .12 • Motion words χ2(2) = 7.53, p < .05 • Insight words χ2(2) = 6.29, p < .05

17. Results – Gender • Motion words U = 414.00, z = - 2.524, p = .012

18. Results – Relationship to suspect • Negative emotion words F (3, 93) = 5.801, p = .001

19. Results – Abuse type • No differences

20. Results – Number of incidents • Motion words U = 677.500, z = - 2.000, p = .046

21. Results – Interview type • Motion words U = 730.55, z = - 3.215, p = .001 • Time words U = 892.00, z = - 2.049, p = .04

22. Discussion • Group differences exist • Age groups most robust • Credibility assessment of children using LIWC • Misleading?

23. Caveats • Ground truth • Matched sample of doubtful cases

24. Acknowledgements • The forensic child lab at the University of Cambridge • The children and interviewers participating in this study • The Gates Cambridge Trust for their generous funding • Joseph Bonneau for his programming assistance

25. Questions?Thank you! For more details and questions please contact Megan Sim mpys2@cam.ac.uk