ABSTRACT
Statistical Significance...................................................... 254 17.2.4 Concluding Thoughts ...................................................................... 254
17.3 Multitrait Derivative Free Restricted Maximum Likelihood Analysis ....... 254 17.3.1 Foundations of the Univariate Case ................................................ 254
17.3.1.1 Henderson’s Mixed Model Equation and the Estimation of Variance and Covariance Components ........................ 254
17.3.2 Study Goals ...................................................................................... 255 17.3.2.1 Choosing a Model Using Akaike’s
Information Criterion........................................................ 256 17.3.2.2 Comparing Nested Models Using Chi-Square Tests ....... 256
17.3.3 Considerations.................................................................................. 256 17.3.3.1 Advantages of Using Multitrait Derivative Free
Restricted Maximum Likelihood Analysis ..................... 257 17.3.3.2 Drawbacks of Using Multitrait Derivative Free
Restricted Maximum Likelihood Analysis ..................... 257 17.4 Concluding Thoughts and Other Uses For Multitrait Derivative
Free Restricted Maximum Likelihood Analysis ......................................... 257 17.4.1 Other Applications of Multitrait Derivative Free Restricted
Maximum Likelihood Analysis ....................................................... 257 17.4.1.1 Genetic Association Studies ............................................. 257 17.4.1.2 Environmental Association Studies.................................. 258 17.4.1.3 Assessing Gene × Environment Interactions.................... 258
17.4.2 Concluding Thoughts....................................................................... 258 Author’s Note ........................................................................................................ 258 References.............................................................................................................. 259 Appendix A: Using Animal Breeder’s Toolkit to Compute Relatedness
Among Individuals within a Pedigree ......................................................... 261
In this chapter we describe our research on the behavior genetics of personality and subjective well-being (SWB) in our chimpanzee cousins, a research program that we plan to extend to the other great ape species-orangutans, gorillas, and bonobos. Although we had been familiar with classic behavior genetics designs before initiating this research, we quickly realized that these approaches were not suitable for studying great apes in naturalistic and semi-naturalistic settings. Our subjects could not be selectively bred, they could not be conveniently grouped into sets of monozygotic and dizygotic twins, and their pedigrees did not resemble trees but, instead, kudzu. Fortunately, we stumbled upon two types of pedigree analysis that allowed us to hack through the familial wilderness and estimate the relative contributions of genetic and environmental effects on individual differences in chimpanzee personality and SWB. The first part of this chapter will describe reasons why the behavior-genetic study of chimpanzees is interesting and compelling. The second part will describe how multiple regression analysis can be used to estimate relevant variance components and will highlight the advantages and disadvantages of this method. The third part will describe the use of mixed-model equations and a restricted maximum likelihood analysis to estimate variance and covariance components. Finally, we will offer concluding thoughts and suggest other potential uses for these analyses.
