Lucas et al (2006) found that participants given easy and hard maths questions are likely to conform to others when the problems are harder. This supports ISI.
In Asch's variation on taskdifficulty, conformity levels increased as people looked to others. This supports ISI.
Schultz et al (2008) found they could change the behaviour of hotelguests by providing printed messages on how to save energy. This supports ISI.
Jenness (1932) demonstrated the power of conformity in an ambiguous situation which supports ISI.