He Hits the Baby, Sits in Time-Out, Then Does It Again
Time-out is failing because, in a house with a newborn, it delivers the exact thing the hitting was after. How to work out what the behaviour is buying, and change the price.

10:40am, and he's looking straight at you while he does it
You're on the sofa feeding her. He walks over from the other side of the rug, unhurried, and smacks his sister on the leg.
And here's the detail that matters more than anything else in this article: he isn't looking at her. He's looking at you.
You do the recommended thing. Calm voice, no shouting, "we don't hit," onto the step, the minutes, then down at his level, then the hug, then the little talk about gentle hands. He nods. He means it, as far as a three-year-old means anything.
Twenty minutes later he does it again.
That's four times today and it isn't lunchtime. You've got a newborn attached to you, you cannot physically enforce a single thing, and you have started to have a thought you'd rather not have in writing: this isn't working, and I think he's enjoying it.
You're probably right. Not about him enjoying hurting her. About it working — for him.
The technique isn't failing. It's being run in conditions it needs and doesn't have
Time-out, as originally described, is short for time out from positive reinforcement. That's the whole mechanism. You briefly remove a child from a good, attention-rich environment, and the contrast is what does the work.
Now look at your version.
The environment he's being removed from is one where his mother is holding somebody else and hasn't made eye contact with him in forty minutes. The step, by comparison, is a place where an adult brings him there, talks to him, watches him, and at the end kneels down and hugs him and speaks softly about feelings for two minutes with no baby in the way.
What exactly is he being removed from?
Attention is one of the strongest currencies a small child has. It isn't that he wants "bad" attention rather than good attention — it's that when the supply drops, any reliable route back to your face is worth using. And you have accidentally built a very reliable one. Cost: one smack. Payout: immediate eye contact, being spoken to, being touched, and a full undivided cuddle at the end.
He's not being naughty. He's being efficient.
Spend a day proving it, before you change anything
Don't take my word for the diagnosis. It might be wrong for your kid.
For one day, write down every incident — nothing elaborate, just a note on your phone with the time and what was happening in the ten seconds before. Where you were. Where the baby was. Whether he'd had you to himself recently.
You may well find the incidents aren't scattered at all, but cluster: during feeds, on the phone, at the nappy change, in the last hour before dinner when everyone's flat. If the pattern is "the moment my attention goes to her," the payoff theory holds and the rest of this applies. If it's random, or if it's mostly during transitions and getting dressed, you may be looking at something else entirely, like being overwhelmed rather than displaced.
One day of notes is worth ten articles, including this one.
Make the currency free, so it stops being worth buying
The generic advice is "give him more one-on-one time," and it's true, and delivered the usual way it does nothing. Because parents deliver it after the incident, as repair — which is precisely when it functions as payment.
The timing is the whole intervention. Attention has to arrive when he hasn't done anything, unpredictably, and unearned.
Front-load the feed. Before you sit down, not after he hits. Two minutes of your face and your full attention, then set him up with something specific — not "go and play," which is a dismissal, but a job. He gets the burp cloth ready. He picks which song. Then you sit down.
Pay heavily for the opposite behaviour. The five minutes where he's near her and gentle usually get nothing, because nothing is happening, because you're finally getting a break. That's the exact moment to look up and say something. "You're being so soft with her hand. She likes that." It feels like praising him for not committing assault. Do it anyway — that's the behaviour you want to become the cheap route to you.
Give him a legitimate way in. Small children hit partly because they don't have a better tool. Teach one and rehearse it when everyone's calm: he can put a hand on your knee, and you'll say "I see you, two minutes." Then honour it, near enough, or the tool stops working.
Drop the drama on the incident itself. This is the one that feels wrong. When he hits, the response should be brief, flat and boring. Turn your body so she's shielded, say "no hitting" once in a dull voice, and then attend to her, not to him. He gets separation without a performance, and no warm reconnection stapled to the end of it. Reconnect twenty minutes later, out of the blue, for no reason.
That delay is doing something specific. It breaks the link between hitting and cuddles without withdrawing the cuddles, which he needs and should keep having.
What one-handed enforcement actually looks like
Nobody writes this part, because it's not a technique, it's logistics.
You cannot carry a three-year-old to a step while wearing a newborn, and you shouldn't try. So change the geometry instead of the discipline. Feed with your back to a wall and him in front of you where you can see him coming. Put the baby on a raised surface when you're not holding her, so she isn't at hand height. Use a sling for the hours you know are bad, because it frees an arm and it also means she's on you, which is safer than her being reachable.
Blocking is a legitimate response. Putting your forearm between them, calmly, dozens of times, is not a failure to discipline. It's the actual job right now.
And the flat rule: they don't get left alone together. Not for the length of a shower, not while you answer the door. Not because he's a monster — because he's three, and impulse control at three is a work in progress, and a newborn has no way to protect herself.
The part you feel worst about
You're starting to resent him. Sometimes you look at him and feel something cold before you feel anything else, and then you feel appalling about it for the rest of the day.
That is not evidence about what kind of parent you are. It's evidence that you're exhausted, healing, feeding around the clock, and being hit at by someone you love while holding someone you love. Resentment under those conditions is a load reading, not a character reading.
It's also worth saying out loud to somebody, because the thing that makes it dangerous is keeping it secret.
If you'd like to think it through at 2am, TrueTalk has an AI advisor called Discipline Coach David, written as a child behaviour specialist and discipline coach whose areas are positive discipline and behaviour change. He's an AI persona, not a clinician, and not a substitute for your paediatrician or health visitor — but he's there at the hour when this is happening and the first conversation is free. Useful for working out what your one day of notes is actually telling you.
And the real limits, plainly. If the aggression is escalating rather than settling over a few weeks, if he's aiming at her head, if it's happening at nursery too, or if he's hurting animals — that's a paediatrician conversation, and soon.
Your own head is a separate route, and it isn't his doctor. A paediatrician treats him. If your mood has gone somewhere dark since the birth, or you're frightened of what you might do when you're at the end of it, that's about you, not about him — ring your GP or your health visitor today and say it in those words, the blunt ones, not the tidied-up version. And if you're having thoughts of harming yourself or the baby, don't wait for an appointment. That's your GP, an urgent care line, or emergency services, now.
Neither of those is an article problem. Both are things clinicians see often and can help with, and both are easier to deal with early than late.
Most of the time, though, this is a small person running a strategy that works, and you're the one who decides what it buys.
Change the price. He'll notice faster than you expect.
