What gets stronger the more you use it?
Answer: Your brain.
The more you challenge your brain with learning, problem-solving, reading, memory tasks, and new experiences, the more practiced and capable many mental skills can become.
The riddle works because we usually think of something becoming worn out when it is used repeatedly. But the brain can improve through regular practice and stimulation.
Just as physical exercise can strengthen the body, mental exercise can help sharpen skills such as attention, memory, and reasoning.
That reversal makes the answer satisfying: instead of getting weaker from use, your brain can become stronger with continued use.
