An example of what ?

Hi~ in the part underlined, is the part in red an example of "social groups" or an example of "an assortment of stereotypical beliefs and attitudes "?

Thanks for your help~

Recent sophisticated assessment methods have established that
people unwittingly hold an astounding assortment of stereotypical beliefs
and attitudes about social groups: black and white, female and male,
elderly and young, gay and straight, fat and thin. Although these implicit
biases inhabit us, they can constantly vary depending on our own group
membership and our everyday environments.