A cornerstone of cognitive science is that mental systems are limited: There is a maximum amount of information they can process or store, beyond which performance breaks down. Yet so far the study of such limits has been focused on core systems like attention and memory. Here we explore self-representation, the ability to represent someone or something as being you. We find a limit on a well-known index of self-representation known as the self-reference effect, whereby people perform better for items that they associate with themselves than with others. This effect does not scale additively when people actively associate stimuli with more than one self-concept at a time (e.g., their younger and older selves, or two hypothetical versions of themselves). This suggests that even though we can self-represent various self-concepts independently, we can never do so for more than one self-concept simultaneously.

What we know as the self is not just one unified construct, but consists of various self-concepts that are continuously created, revised, and discarded, such as “woman”, “Thai national”, “Northwestern student”, and “true self”. These rich, variegated self-concepts help organize our endeavors throughout the different domains of our lives. How do we store information associated with each of these self-concepts without confusing them in long-term memory? We uncover two mechanisms that support this ability— one that arises from the nature of long-term memory processing, and the other that arises from the nature of self-referential processing. Specifically, people are less likely to confuse memories for self-concepts that are more distinct, and they are more likely to remember information for the self than for others. Together, the studies shed light on the mechanisms that support our impressively rich store of self knowledge.