OK, so the rather tragic story is that a woman (Jessica) died a few days after giving birth. No-one realised there was anything seriously wrong with her in time. Her doctor gave her painkillers for sciatica, which masked her symptoms (don't doctors watch House?), and her husband believed she was tired and sore because she'd just had a baby. Actually, she had a streptococcus A infection of the womb which a simple dose of antibiotics would have cured — if it had been detected in a timely manner.
So, given this background, what is the sub-header saying?
Well what it should be saying is something like: "because he was so focused on the birth, he didn't realise Jessica was dying". However, it isn't saying that. It would say that if it had a comma after "dying", but it doesn't have one. What it actually says is something along the lines of: "He didn't realise that the reason Jessica was dying was because he was so focused on the birth".
When you re-read it that way, now you see what I mean. Yet, be honest, when you read it the first time, you understood it in a way that matched the story, yes? You didn't even have to think about it. Even though the punctuation favoured the other meaning, you overrode it and went for the more likely version — but you didn't need to think about it, did you? You just did it automatically.
I got both readings simultaneously and chose the right one because it "felt" better. I didn't have to think about it in words, but I was conscious of making the decision, it didn't just slop right by as it would have done if it hadn't been partially ambiguous.
This happens a lot with me: when given a statement with a number of possible meanings, I get pretty well all of them thrown at me at once. Other people seem to be able to glide through serenely, their subconscious mind having done all the disambiguation without the need to bother their conscious mind, so they can concentrate more on what's being said. That doesn't happen with me, which is one reason why it takes me forever to do cryptic crosswords — there are just too many ways to read the clues.
It's an input-only thing — I'm just as likely to write an ambiguous sentence as anyone else — and although other people seem to have a better time of it, I'm not actually complaining; I quite like having multiple ideas at once, it's only occasionally frustrating, and I can easily live with it. It's odd that there is a difference, though.
I wish I could have found a less unfortunate example to use to illustrate my situation, but this was the one that made me think about it, so it's what I went with.