For anyone in social psychology using the Inclusion of the Other in the Self (IOS) Scale to measure self-other merging, you might have wished that you could know for sure how much self-other overlap there is between your participant and a target group or individual.

Indeed, the IOS response choices go from 1 to 7 only, and unfortunately these don’t match the percentage overlap from the circle images (i.e., 1/7 is not 14% overlap, and 7/7 is not 100% overlap). You can observe this on the original IOS scale below.

So through trial and error (using the VennDiagram package), I was able to determine the approximate actual overlap from the pictures (below).

I feel like the overlap is pretty close to the original scale. Based on this, I used the approx() function to interpolate any responses so that 1 = 0% (overlap), 2 = 10%, 3 = 20%, 4 = 30%, 5 = 55%, 6 = 65%, and 7 (the maximum) = 85%.

But that also means that a continuous response (for example based on a group average) can also be plotted accurately (e.g., a score of 6.84 would turn into 81.8 % overlap). Let’s see a few examples.

But first, let’s source the function from my github:


Score of 1 (0% overlap)

Score of 3.5 (25% overlap)

Score of 6.84 (81.8% overlap)

Changing labels

You can also change group labels with the categories argument, although ‘Self’ and ‘Other’ are the defaults.

Saving to file (PDF or PNG)

Example figure

This allowed me for instance, for one study, to compare three of my groups side-by-side following an intervention:

Concluding Statement

You can always edit the function to suit your purposes, or contact me for questions or requests to modify this function at remitheriault.wixsite.com/site/contact! Thanks for reading my guide! :) \(~\)