Well, my faith in childhood sensibility has been restored.  Of lactnetters
who responded to this scenario:

"Johnny broke one teacup throwing it at his sister.  Sara broke eight
teacups helping Dad load the dishwasher.  Which kid did the worse thing?"
here were the responses (which kid did the worse thing).  One wise
lactnetter posed the problem using boys for both parts.

Age    Johnny     Sara
10      2
9       1
8       1               (first said Sara, then changed his mind)
7       2           1
6       2
5.5     1
4                   1   (two this age didn't understand the question; one
wanted to know who in her own family had done this!)
3.5     "they're *both* bad."

So it seems, based on this vast sample, that children who are raised in the
average American family develop this particular moral sense later than
children who are raised in families that tend to nurture at breast.  Is
anyone surprised?  If more of you will send me responses from children up
thru age 8 or 9 (with age of weaning, to make it juicy), and if the pattern
holds, I'll send it to the person at Yale who posed the scenario (and who
wasn't clever enough to make both children the same sex - does a good
future Little Miss Homemaker break cups?  is it more acceptable for a boy
to do so?) and suggest she add a variable to her future research...

Diane Wiessinger, MS, IBCLC  Ithaca, NY, who is tempted, based on the
relative permanence of the actions, to prefer Johnny's behavior.  My son
has only a tiny scar from where his brother heaved the chunk of driveway
stone many years ago;  the dinner plate a middle-school girl broke for us
is gone forever...