The problems with linguistic credibility assessment of children

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