Does “thinking” not include all mental activity?
Is this accurate?
Mental speech and using your imagination to picture things are included in mental activity. When someone tells you “Think about it.”, you don’t have to use mental speech to do it. You don’t have to use your imagination to picture things to do it. However, if you do use mental speech and/or use your imagination to picture things when someone tells you to “Think about it.”, using those things are also part of the thinking process. Mental activity is also included in all things that involve the mind.
Thinking could be argued to mean "intentional thought", such as recalling a memory or working through a math problem or trying to come up with something to say.
Mental activity seems to cover more ground; I'd interpret it to include things like sensation (feeling pain and cold, even if you're not attending to them) and emotion (such as anxiety).
Depending on which system you're using, "thinking" may include all mental activity or only a small sliver of it.