In the article "Seeing colours in numbers" (The Hindu, Sci Tech feature, Sept 18, 2003), there is a claim that "faulty gene allows leakage of information between the two adjacent areas responsible for seeing colours and identifying numbers. This aberration makes some people see colours in numbers."

But second part is more interesting. Prof. V.S. Ramachandran, Director of Centre for Brain and Cognition at the University of California at San Diego, comments also on Being aware of awareness as a capability only with human beings and not other animals. But I couldn't get a clear idea though.