What are demand characteristics and how can they be minimised?

Demand characteristics are the clues in an experiment which could convey the purpose of the research to the participant. Participants will be affected by: (i) their surrounding: (ii) the researchers characteristics: (iii) the researchers behaviour (e.g. non verbal communication), and (iv) their interpretation of what is going on in the situation.   Participants have expectations about any experiment and may try to deduce the purpose of the experiment. This gives rise to the potential of them responding in a way which supports the hypothesis being tested. 

There are steps experimenters can take to attempt to minimise the chance of demand characteristics, such as carefully following standardised procedures and keeping the environment as natural as possible. You could even use different experimenters to see if they obtain similar results, as the experimenter may unconsciously convey to participants how they should behave.