  In this paper, we study, information theoretically, the impact of transmitter
and or receiver cognition on the channel capacity. The cognition can be
described by state information, dependent on the channel noise and or input.
Specifically, as a new idea, we consider the receiver cognition as a state
information dependent on the noise and we derive a capacity theorem based on
the Gaussian version of the Cover-Chiang capacity theorem for two-sided state
information channel. As intuitively expected, the receiver cognition increases
the channel capacity and our theorem shows this increase quantitatively. Also,
our capacity theorem includes the famous Costa theorem as its special cases.
