Table 1.

Phases of the experiment and their specific characteristic.

	Level	Time	Stimulus	Task/reward for	Learning criteria
Habituation	0	One session	None	Stay 5 min in the box and eat wheat grain ad libitum	None
		One session	None	Stay 10 min in the box and eat wheat grain ad libitum	None
		One session	None	stay 10 min in the box and eat wheat grain ad libitum, turning on and off of reward delivery system	None
		One session	None	Stay 15 min in the box and eat wheat grain only when reward system turns on, time to eat 20 s	None
		One session	None	Stay 15 min in the box and eat wheat grain only when reward system turns on, time to eat 5 s	None
Screen training	1	Individual	Circle	Peck on circle or no peck on circle within 30 s – rewarded	80% Correct
	2	Individual	Circle	Peck three times on circle – rewarded	80% Correct
	3	Individual	Circle	Peck five times on circle – rewarded	80% Correct
Discrimination	4	Individual	Bars	Peck five times on correct symbol – rewarded	80% correct
Reversal	5	Individual	Bars	Peck five times on correct symbol – rewarded	80% Correct
Extinction	6	Individual	Bars	No response, not rewarded	70% Correct

The amount of sessions a hen needed for screen training and the learning phases depended on the individual learning behavior.