This problem is equivalent to his ability.

He found a sculpture of a double-headed dragon.

He instinctively scratched his head when faced with a difficult problem.

He scratched his head when faced with a difficult problem.

It's surprising that he can run so fast.

What? I couldn't catch what you said.

Could you bring me that, whatchamacallit?

This book is difficult to understand because it contains many difficult words.

When a baby starts babbling, it's the initial stage of language acquisition.

His baby is babbling.