The work-for-food and work-for-money tasks were programmed
using E-Prime 2.0 (Psychology Software Tools, Inc. Sharpsburg, PA,
USA), and run on networked PCs with 17-in colour monitors and
standard QWERTY keyboards. Instructions were presented in black
font on a white background. For the work-for-food task these were
as follows. First screen: ‘Pizza bar pressing task, please wait for in-
structions.’ Second screen: ‘Starting in 30 seconds you will have one
minute in which you can earn FOOD (pizza) by pressing the SPACE-
BAR. The more times you press the more FOOD (pizza) you will earn.
The maximum amount you can earn is a whole pizza (8 slices). To
maximise what you can earn start bar pressing as soon as you see
the red count-down clock appear below. Have your finger ready at
the SPACEBAR.’ Third screen: ‘KEEP PRESSING THE SPACEBAR. The
more times you press the more FOOD (pizza) you will earn.’ A digital
clock displayed the number of seconds remaining. Final screen:
‘Thank you for completing the task. Please wait for further instruc-
tions from the Experimenter.’ Each sentence of these instructions
appeared centred on a separate line(s) on the screen. The total
number of space bar pressesmade in the designated 1-minute period
was recorded. The work-for-money task was the same as the work-
for-food task except that the first screen was headed ‘Money bar
pressing task’, and MONEY (£££££) replaced FOOD (pizza) on the
second and third screens. In addition, on the second screen it was
stated that ‘The maximum amount that you can earn is £5.’