Ralph used to get quite a "buzz" from a single cup of coffee. Now he finds that he can drink up to four cups without even noticing the effects of the caffeine. This would suggest that Ralph:

Ralph body is addicted (negatively resisted) to high Caffeine consumption

Explanation:

When a person keeps on consuming too much of a good, the body becomes resistant to it. So, the effect of consumption keeps on fading away with more & more increase in consumption amount.

This can be illustrated with case of addiction goods (alcohol). A beginner alcoholic has much less capacity than a pro alcoholic. Another example could be the case of excessive use of antibiotics. This makes the bacterias/ germs - earlier so responsive to antibiotics, resistant to them. So, effectiveness of antibiotics fall.

Ralph case is very similar to above examples. His caffeine consumption has increased so much that his body has been accustomed to excessive caffeine consumption, & hence the effectiveness of more caffeine (in terms of buzz) has reduced.

can you explain it better

answer; /// you data to develop general ideas or theories;