I think they respond to emotions A LOT. They are very into loving.
It also depends on the breed, and whether they were incubator hatched (no bonding) vs momma hatched (bonding). Some chicks who were hatched in a kids' shirt or under a motherly cat are just as bonded to others as chicks that were hatched under a hen. Some incubator chicks from TV rooms in houses bond really well if somebody's around to cuddle with and talk to.
But I have a neighbor who said her hatchery chicks never could figure it out; flighty breed + no opportunity to bond = skittish birds who run away all the time. Our birds pretty much ASKED us to take them home, they were pets first, and trained us, not the other way around. If they had been skittish or hard to get close to, it wouldn't have happened at all.
We took ours home from a Rare Breeds Farm Show at a local museum, from some 4H-ers. Maybe that's a good way to find birds who are already friendly?