It is the essential property of the IAPS that the stimulus set is accompanied by a detailed list of average ratings of the emotions elicited by each picture.
The normative rating procedure for the IAPS is based on the assumption that emotional assessments can be accounted for by the three dimensions of valence, arousal and dominance.
[3] Thus, participants taking part in the studies that are conducted to standardize the IAPS are asked to rate how pleasant/unpleasant, how calm/excited and how controlled/in-control they felt when looking at each picture.
[16][17] To maintain novelty and efficacy of the stimulus set, the IAPS images themselves are typically not shown in any media outlet or publications.
[18] A group of researchers at Harvard University has published an alternative set of images that they claim to be comparable to the IAPS in 2016.