We present two neuroscience experiments that have major implications for HCI research: First, we discuss a functional Magnetic Resonance Imaging (fMRI) study by Sanfey et al. (2003) who investigated brain activities of players of the Ultimatum Game. It was found that participants had a stronger emotional reaction to unfair offers from humans than to the same offers from a computer. Second, we discuss a Positron Emission Topography (PET) study by Haier et al. (1992) who studied participants playing the computer game Tetris over a period of several weeks. It was found that learning may result in decreased use of extraneous or inefficient brain areas. Finally, we stress the importance of measuring theoretical constructs in HCI research (e.g. user satisfaction) by using neuroscience techniques. Since theoretical constructs are neither directly observable nor objectively measurable, we argue that recent achievements in neuroscience technology will allow for directly measuring feelings and thoughts (e.g. satisfaction) in the future.