To study animal behavior, scientists utilize proximate explanations which focuses understanding on immediate causes of behavior, and ultimate explanations which focuses on evolutionary causes. Tinbergen posed four questions that focus on proximate and ultimate explanations: What mechanism caused the behavior?, How does the behavior develop?, What is the function of the behavior?, and How did the behavior develop? Methods to study behavior include observational, experimental, and comparative methods. Observational methods involve observing and recording behavior without manipulating the environment or animals. Experimental method involves manipulating a variable to examine how it affects the behavior of the animal and utilizes independent variable, dependent variable, and a control group. Comparative method compares behaviors between species to understand evolution of behaviors. This method uses phylogeny, diagrams indicating evolutionary ancestor descendent relationships, and sister species. In phylogeny, ancestral traits, found in a common ancestor, and derived traits, common in more recently evolved species, are observed by researchers. Scientists used comparative psychology, the study of animal behavior in a comparative manner across a species, to understand human minds. It includes behaviorism that studies behavior independent of animal consciousness. Lastly ethical animal use revolves around replacement, reduction, and refinement.