Chick doesn't hear properly?

Hello,

We've had six little chicks for two days, but one of them is acting strange.

It doesn't really listen to its mother's call and takes a long time to realize something is happening. While the others stay close to the chicken, the chicken doesn't seem to notice that she's moving away and otherwise just stands there, looking rather dreamy and reluctant. If the chicken does manage to lure it to her, the little one tends to search for something edible on its own rather than letting her show it.

It also never calls for its mother, which chicks that age usually do for the smallest thing. It does seem to respond to sounds, but if I say something or the other chicks chirp, its reaction is the same as if it were its mother calling: if it's dozing, it'll just open its eyes briefly to see if anything's happening, and then go right back to sleep.

He also doesn't seem to mind if you pick him up. The only thing he does is cry if there's no 'cave' to snuggle in. He doesn't care who the warmth comes from.

So could it be that it can't hear properly? Or is there something like autism in chickens? Is there a way to determine this?

thanks in advance