Confirmation bias isn’t about expectations (that would be placebo effect), it’s about how you understand outcomes.
Confirmation bias means that you’ll notice and weight evidence that conforms to your view more than evidence than contradicts it.
All that said: sounds like your husband was being grumpy and I think it’s fair to be irritated. However, if you’re suffering from insomnia, stop drinking so much coffee, especially that late.
It’s not too much from my perspective. I drink more tea than coffee (tea at home, coffee out) but I drink good black tea and I leave the bag in my cup. My mug of choice is a big 12 ouncer. I pretty much start drinking tea at 6 am or so when I get up, and I continue all day. I’m guessing I have as many as 8 in a day, and often the last one is as I’m reading in bed. I drain that last cup, turn off my light and go to sleep.
Yes, sometimes I have sleepless nights. I attribute that to being over 50 as much as anything, and in the recent past to the stress of moving to a new state and new job. Since the move I’m back to sleeping like a log (unless I end up as a launching pad for the cats, but that’s for another thread 
)
So IMO your husband was out of line. Not in his concern, perhaps, but in his delivery and his assumptions.
Is that you Lonesome George? 
I had a SO who drank coffee all day and said it didn’t affect her- but she skittered around like a crack head.
She didn’t sleep well, and my attempts to convince here to taper off the coffee had mixed results.
Am I a controlling asshole? No.
She said she couldn’t sleep, and I pointed out what was stopping her.
I never once actively DID anything, I just asked “Coffee so late? Not going to sleep tonight?” or similar.
Eventually she settled on not drinking coffee after dark- and slept a lot better after that.
I can’t believe it took 17 posts for somebody to point this out.
Isn’t decaff an option for your night time drinking? Or if you simply MUST have caffeine, you might want to rethink your views of coffee intake.
Alcoholics have a proclivity for justifying their drinking habits too.
I think decaf would be fine, but its not about the coffee.
The insomnia is occasional and doesn’t seem to be correlated to coffee consumption.
I’m glad to hear there are other caffeine consumers who also sleep well.
Here’s the real point. If you share a bed & you don’t sleep well, then he might not either. Sleep-deprived cranky asshat could technically describe his change in behavior (if he was a jerk, you wouldn’t have started
up with him so I’m going to assume his behavior is something as new as your insomnia is too). I’m wondering if its too late to hijack this thread to solicit suggestions to get you a better nights sleep.
I used to hear people say that exercise to the point where you are approaching sleep as tired was a good solution.
Still, 9 out of 10 Dopers will agree that beating the ever-loving snot out of your husband before bed just to get a good nights sleep is probably a bad idea.
Sigh “I feel SO much better already! I should have done this Years ago…!”
My late wife used to drink a cup of coffee in order to go to sleep. Not every night, but often enough that it was notable. She slept well. In fact, I don’t recall her ever having ‘the jitters’ after drinking coffee. I, on the other hand, will stare at the ceiling all night long if I drink coffee after mid-afternoon. Everyone’s brain is different.
I second (or third or whatever) the idea of bringing up this subject with him when it isn’t a trigger point for an argument.
I drink a vast amount of coffee and it never prevents me sleeping - my wife and daughter will not sleep at all if they have a single cup in the afternoon.
IMO, it could be that there is a correlation that is for some reason easier for others to see than for you - we unintentionally blind ourselves to all sorts of minor behaviours that are obvious to others around us.
It could be (for example) that you’re more sensitive to spikes of caffeine intake than you are to the total amount consumed in a day. Actually, I have no idea if there could be any medical basis for such a thing, but it’s just a hypothetical - maybe your SO has noticed that your insomnia seems aggravated on any day when you’ve taken multiple coffees in succession.
Be careful before you rule out the possibility that someone else has noticed something about you that you yourself have not, is all I’m saying.
(Emphasis mine) Somebody close to you seems to think that it may be.
Yes, there are people who can have caffeine and sleep fine. But you’re self-admittedly not sleeping fine and choosing to dismiss a really common cause of sleep difficulties. Perhaps you could be more open to the possibility that someone close to you is making connections that you don’t see. It is absolutely possible that caffeine in combination with other factors can disrupt sleep, so while caffeine may not bother you every time, it can still be a contributing factor.
Don’t forget that insomnia affects the person you’re sharing the bed with, just like snoring does. He has a stake on how well you sleep, too. He may not have brought it up in the best possible way, but it doesn’t make his underlying concern wrong.
If it’s not about the coffee, then have water or juice in the evening.
I’m happy to admit that coffee could contribute to the insomnia (and probably does in combination with other stresses) And it’s possible that SO’s argument has some merit but when I said it’s not about the coffee, I meant there are other dynamics in our relationship that have caused an irrational overreaction to a couple of cups of instant coffee.
It’s interesting to note there are several people here, or who know people whose sleep is not adversely affected by coffee.
But those people don’t have occasional insomnia.
No one doubts that some people aren’t affected by coffee. That’s not disputed. I’m not sure why you keep bringing that up.
If there are other problems in your marriage, well I guess that’s a different issue then.
Well, sure. Young people, in particular, are notorious for being able to down multiple cups of coffee at midnight and sleep like babies immediately after. I used to be one of them! Then I turned 35… 
Also, consider that brain chemistry is a weird thing. Doctors write prescriptions for stimulant drugs for thousands of children every day…to help calm them down. There are medical conditions where stimulants work in the “opposite” way they work for most of us, and sometimes those are undiagnosed and self medicated with caffeine.
Weird double post.