Also, it was a standard practice to castrate young boys inorder to produce superior sounding song voices. Laboratory experiments have the advantage that they systematically control for variables that might influence the outcome of our experiments. Thus, it is less difficult to interpret the results. Also, these studies can easily be replicated. However, the disadvantage is that it is easy to lose external validity.
Field experiments are advantageous in that they have high validity.
However, they lose specificity. It may be impossible to determine if the behavior we are seeing is the result of a hormone or some other variable such as light or temperature. In the best of all possible worlds, we would use field studies to determine potential variables of interest, examine them closely in the laboratory, and then return to the field to see if our results are valid. To affect behavior, hormone must eventually interact with brain.