Comparison
In-Group Bias vs Outgroup Homogeneity Bias
Main difference in one sentence
In-Group Bias gives your own group extra trust or lenience, while Outgroup Homogeneity Bias flattens another group into sameness.
Brain Shortcuts that Tilt Judgment
Cognitive Biases
In-Group Bias bends judgment in favor of insiders. Your side gets more patience, more credit, and more benefit of the doubt.
People Mistakes
Social Perception Errors
Outgroup Homogeneity Bias strips variety from outsiders. The other group gets described as one type instead of many individuals.
Example where people confuse them
A student says their own club is full of different personalities but treats another club as basically all the same. That is Outgroup Homogeneity Bias because the outside group is being flattened. If the student also excuses rude behavior from their own club more than they would excuse it from the other club, that is In-Group Bias because insiders are getting special grace.
Quick memory trick
In-Group Bias says, "My side deserves more trust." Outgroup Homogeneity Bias says, "Their side is basically all the same."