Scale development and construct validation of a chimpanzee rating scale



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The last two decades have seen a surge in published research on primate personality. This surge contrasts with the paucity of research over the preceding century. People interested in primate personality research come from a broad range of fields, but they are all interested in measuring primate personality in a way that is reliable, valid, and practical. This dissertation aims to describe the development and evaluation of the construct validity of a new rating scale in chimpanzees. The scale is based on a bottom-up approach to scale development and was developed using steps from both Uher (2008a,b) and Gosling (1998). As described in Chapter 3, the scale was evaluated by using it to rate 143 chimpanzees at the University of Texas MD Anderson Cancer Center Facility in Bastrop, TX. Twenty-one people who have worked with the chimpanzees between 6 months to 20 years rated the chimpanzees. Chapter 4 describes how inter-class correlation coefficients (ICCs) were used to calculate the reliability of the items on the scale. There was only one item (predictable) that turned out to not be reliable. The other 40 items were included in subsequent analyses. An exploratory factor analysis, as described in Chapter 5, was performed in order to determine the structure underlying the scale. Five methods were used to determine that a six-factor solution fit the data best. The six factors were labeled Reactivity, Dominance, Openness, Extroversion Agreeableness, and Conscientiousness based on the degree to that they correlated with other previous chimpanzees scales that used those labels. The convergent and discriminant validity of the factors was evaluated, as described in Chapter 6, by looking at the predicted relationships between each of the six factors and the variables of sex, age, rearing history, behavior in reaction to a novel stimulus, general behavior, injuries, illnesses, blood chemistry, and cortisol. The results indicate that there is a lack of evidence for convergent validity, but some evidence for discriminant validity of the new chimpanzee rating scale. The discussion in Chapter 7 focuses on the findings from the study as well as strengths and limitations of the new chimpanzee rating scale.