I'd love to know how babies know the second you put them down. It doesn't matter how hard they were sleeping before you put them down. They still know. Not only do they know, though, they wake up. This isn't always a bad thing. My son about one quarter of the time wakes up and is in a pretty good mood. About half the time he wakes up hungry. This equates to some fussing but nothing overly serious and remedied with ease.
It's that last quarter that drives me crazy. You know, when they wake up screaming and you can't figure out why. At least I haven't been able to when my son does this. Granted, the last few days I know why he's been crabby. However, seeing as it was thrush, the best I could do was give him his medication like the doctor said and leave it at that. But that doesn't help in the immediate moment much. Lucky for me he's just about over it. I'm hoping that cuts down on the odds of him waking up with a tantrum.
And, trust me, attempting to reason with a 6 week old child just doesn't work. Particularly when they are sounding more like an air raid siren than a tiny infant. For you non-parents out there, you're probably laughing at me saying 'No kidding!' right about now. Anyone who's parented a child through this age understands. Either that or I have gone crazy.
In the end I've resigned myself to the fact that infants somehow have hardwired sensors that tell them when you put them down. Each time I put my son down, I pray that when he wakes up, he won't be in a bad mood and that he'll go back to sleep right away.
Sometimes I even get that prayer answered...