No, I do not think women overthink things, so much as land on an incorrect assumption and trying to support it as truth. Men can do this as well, but women seem more likely to prize themselves on their ability to "read" people, or grasp the "hidden meaning." So what do I mean?

FACTS: There could be hundreds, or thousands, or an infinite number of reasons as to why something happens. Or in this case, why someone says something, or what they are actually thinking. You will never know what that other person is thinking, or HOW they are thinking it (we each think differently, the same way there are different meanings in different cultures - their action may not mean the same thing to them as it does to you).

So

SOLUTION: We tend to rationalize to a great extreme. We fill that lack of certainty with our own experiences, or our own hopes. So jayjay says he can't meet next Saturday. In his mind he's thinking about whatever he's got to do Saturday, and when he's next available. She hears "I can't meet next Saturday" and nothing else, none of what's going on in his mind. She's feeling a little insecure. So without that certainty (from familiarity or whatever) she fills that in with her own concerns and deduces that he really means he's not interested.

I tend to think of overthinking as just spinning your wheels pointlessly on something obvious - more of a different issue. And I'm not saying take everything at face value, more that we should just accept we're not mind readers and will never (at least not without spending a lot of time with someone) have clear insight into what they're thinking. So all of this "reading between the lines" can be fun, but ultimately pointless, and even harmful to a relationship in the extreme.

Yeah! I really sound like I know what I'm talking about!