I don't feel psychologically similar to a chicken in the same way that I feel psychologically similar to other humans.

I don't either, but unless I can come up with a sharp and universal criterion for distinguishing all chickens from all humans, chickens' psychological alienness to me will seem a difference of degree more than of kind. It's a lot easier to argue that chicken suffering matters less than human suffering (or to argue that chickens are zombies) than to argue that chicken suffering is completely morally irrelevant.

Some chickens may very well have more psychologically in common with me than I have in common with certain human infants or with certain brain-damaged humans; but I still find myself able to feel that sentient infants and disabled sentient humans oughtn't be tortured. (And not just because I don't want their cries to disturb my own peace of mind. Nor just because they could potentially become highly intelligent, through development or medical intervention. Those might enhance the moral standing of any of these organisms, but they don't appear to exhaust it..)