Uses multiple sources to examine differences C. Hughes, Dunn, J. (1998) Understanding Mind and Emotions: Longitudinal Associations with Mental-State Talk Between Young Friends Uses longitudinal data to clarify experimental theory of mind research Expect both individual and age differences to correspond to differences in theory of mind Examined children at three time points, from age 4-5, both in friendship dyads and experimental tasks Strengths Uses multiple sources to examine differences Longitudinal design allows analysis of change Weaknesses Some dyads changed when children moved Repeating experimental tasks might lead to practice effects Children improved considerably over the year, with ceiling effects on one experimental task(deception) Individual differences between conversation in dyads and experimental tasks were correlated and stable over time Children used more mental-state talk with age, and use mental-state talk more for reference to shared or others mental-states