Lorenz split a large clutch of greylag goose eggs
into 2 groups.
One was allowed to hatch normally and the
goslings followed their mother around.
Lorenz had the second group of eggs incubated and
then arranged it so that he was the first thing the goslings
saw when they hatched. From then on they followed him
The goslings had formed a picture (imprint) of
the object they were to follow.
When he marked the goslings as to which
group of eggs they had hatched from and then let them out together
from an upturned box, each gosling went straight to its 'mother
figure'. Lorenz' goslings showed no recognition of their real