Lorenz split a large clutch of greylag goose eggsinto two 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 thingthe goslings saw when they hatched. From then on they followed him everywhere.
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 outtogether from an upturned box, each gosling went straight toits 'mother figure'. Lorenz' goslings showed no recognition of their real mother.