Subject: What are the energy requirements of thought?

I'm not sure if this is a neuroscience or general biology question, so sorry in advance.

Is it known how many calories human thinking takes? I see in your archives that the brain uses 10% of 
the body's energy, and I've heard that our brains draw 25% of our blood flow, and that 25% of the heat 
radiated from our bodies is radiated from our heads, but is this true for all mammals? For all primates? 
How many calories are consumed by the "higher functions" of the brain that are special to humans, and 
how many by the parts that are found in other mammals?

Re: What are the energy requirements of thought?