  We consider a model for the evolution of cooperation in a population where
individuals may have one of a number of different heritable and distinguishable
markers or tags. Individuals interact with each of their neighbours on a square
lattice by either cooperating by donating some benefit at a cost to themselves
or defecting by doing nothing. The decision to cooperate or defect is
contingent on each individual's perception of its interacting partner's tag.
Unlike in other tag-based models individuals do not compare their own tag to
that of their interaction partner. That is, there is no {\em self-matching}.
When perception is perfect the cooperation rate is substantially higher than in
the usual spatial prisoner's dilemma game when the cost of cooperation is high.
The enhancement in cooperation is positively correlated with the number of
different tags. The more diverse a population is the more cooperative it
becomes. When individuals start with an inability to perceive tags the
population evolves to a state where individuals gain at least partial
perception. With some reproduction mechanisms perfect perception evolves, but
with others the ability to perceive tags is imperfect. We find that perception
of tags evolves to lower levels when the cost of cooperation is higher.
