The frequent use of gain or loss scores as measures of the amount of learning and forgetting in motor skills was discussed. Learning is redefined as a gain in habit strength (forgetting a loss), with habit being a hypothetical construct representing the internal state which is learning. The use of gain scores is discussed in terms of the “physicalism-subjectivism dilemma,” concerning the fact that the relationship between gains in performance and gains in habit strength (learning) is not known causing meaningless interpretations about the amount of learning. The dilemma has great consequences in studies of individual differences in learning, but is important in experimental designs as well. Some possible solutions to the dilemma are discussed.