Report on misleading information

I am doing a report on a recent experiment I did and I need studies to put into my introduction. My experiment investigated the effect of instructions on participants stress levels. Participants were given instructions which either described the task to be easy or hard and were then asked to carry out the same task . It is expected that participants that were told the task was hard would have higher stress levels. I have already mentioned Loftus and Palmers studies but need some more. Any suggestions please?