Dr. Joyner and Dr. Williams are debating different techniques to measure memory. Dr. Joyner's research uses a serial recall task, where participants are required to remember a series of images and the order they were presented. Dr. Williams' research uses a task where participants must recognize images they viewed earlier in a collection of images. Each researcher believes their technique is better. What aspect of research methods are the researchers debating?

Group of answer choices:
a) The validity of using neuropsychological data
b) How to best compute a savings score
c) The appropriate operational definition for memory
d) The appropriate conditions of the independent variable