Answer:
The idea that different people need different training methods is derived from the premise that they have different learning styles.
While the wide range of often competing theories regarding learning styles exist, one of the popular once, is the theory of Learning modalities developed by Walter Burke Barbe. It suggests that there three learning modalities: visual, kinesthetic/tactile and auditory. For example, I consider myself an auditory learner. I perceive, understand and retain information most effectively by auditory means: listening to lectures, audiobooks, discussions.
The other popular theory of learning styles is Kolb's experiential learning model, which suggests that there are Accommodating, Converging, Diverging and Assimilating learning styles. It is based on the premise that there are two ways of grasping experience - through Reflective Observation and Active Experimentation.
Many of the learning styles theories and models receive criticism, which has to be taken into account.