Fig. 7.

Pleasure electrodes or not? Comparison of famous examples of controversial ‘pleasure electrodes’ in rat (from Olds 1961) and in human (patient B-19, a young man, from Heath 1972). Thick black lines show the electrodes (insulated except at tip; red dots indicate their stimulating tips). Both the rat and the human pressed for electrode stimulation up to thousands of times, but recently questions have been raised whether both electrodes might have produced merely a pure form of ‘wanting’ (incentive salience) rather than actual ‘liking’ (true hedonic pleasure). Reprinted from Smith et al. (2008)