Supernormal stimulus  A supernormal stimulus or superstimulus is an exaggerated version of a stimulus to which there is an existing response tendency, or any stimulus that elicits a response more strongly than the stimulus for which it evolved. For example, when it comes to bird eggs, they can evolve to prefer the artificial versions to their own, particularly evident in brood parasitism, and humans can be similarly exploited by junk food. Organisms tend to show a preference for the stimulus properties (i.e. size, colour, etc.) that have evolved in nature; but when offered an artificial exaggerated stimulus, animals will show behaviour in favour of the artificial stimulus, over the naturally occurring stimulus. A variety of organisms that display or are susceptible to supernormal stimuli include insects, birds, and humans. Supernormal stimuli are present in areas of biology and psychology, but are also studied within other fields like sociology and art. British academic Nigel Spivey demonstrates the effect in the first episode of the 2005 BBC documentary series "How Art Made the World" to illustrate neuroscientist Vilayanur S. Ramachandran's speculation that this might be the reason for the grossly exaggerated body image demonstrated in works of art from the Venus of Willendorf right up to the present day. Animals exhibiting, or responding to, characteristics that represent a supernormal stimulus usually display them as a result of selective pressures. Co-evolution between animals displaying supernormal stimuli, and the organisms responding to the supernormal stimuli, rely on evolution and propagation of genetics, behavioral patterns, and other biological factors. Supernormal stimuli such as emphasized color, size, patterns, or shapes, are often successful because an organism that exhibits them will often be selected by an organism that favors it. This will ensure survival and increased reproductive fitness of current and latter generations. In the 1950s, Konrad Lorenz observed that birds would select brooding eggs that resembled those of their own species but which were larger. Niko Tinbergen, coined this term through his research, which discovered that experimenters could display an alternate target that attract an organism's attention more so than the naturally occurring target. Tinbergen studied herring gulls, and found the chicks peck at the red spot located on their parent's bill. The offspring targets the red spot due to the contrast of color (stimulus). They do this in order to receive food through regurgitation from the parent. Tinbergen and colleagues developed an experiment that presented different models to chicks and determined their pecking rates.