Trait ascription bias is the tendency for people to view themselves as relatively variable in terms of personality, behavior and mood while viewing others as much more predictable in their personal traits across different situations. This may be because our own internal states are much more observable and available to us than those of others.
A similar bias on the group level is called the outgroup homogeneity bias.
- Kammer, D. (1982). Differences in trait ascriptions to self and friend: Unconscious founding intensity from variability. Psychological Reports 51, 99-102.