Celebrity Caricature

Ramachandran and Hirstein suggested that caricature is related to peak shift. In the peak shift effect, animals sometimes respond more strongly to exaggerated versions of the training stimuli. For example, if a rat is trained to respond to a rectangle of a particular aspect ratio, and to avoid a square, when later presented with several rectangles it will prefer the one with the most elongated aspect ratio (this being the one that is most different from the square) rather than the original rectangle used in training. Ramachandran and Hirstein speculated that cells in a monkey brain that respond to particular faces would respond more strongly to caricatured versions of the face. This effect has been confirmed in FMRI experiments by Tsao.
Beside the political and public-figure satire, most contemporary caricatures are used as gifts or souvenirs, often drawn by street vendors. For a small fee, a caricature can be drawn specifically (and quickly) for a patron. These are popular at street fairs, carnivals, and even weddings, often with hilarious results.