Where all participants take part in both conditions
strength :
Participant variable problems are avoided because all participants take part in both conditions . Therefore it doesn't matter if they have different IQ’s because it is kept constant between the two.
This experimental design requires fewer ppts because the same group is re-used
weakness:
Order effects are very likely to occur : ppts may become bored , aware of aims or tired because they carry tasks out twice.
Demand characteristics are more likely to occur because ppts have been exposed to both conditions of the experiment and therefore may pick up on cues .
The researcher will need to ensure they have different test material for condition 1 and 2