A tendency of certain personality traits to have an overwhelming effect in impression formation, even influencing the interpretation of other traits associated with the person being judged (an atmosphere effect). The phenomenon was discovered in 1946 by the Polish-born US psychologist Solomon E(lliott) Asch (1907–96), who presented one group of judges with a description of a target person who was described as intelligent, skilful, industrious, warm, determined, practical, and cautious and another group of judges with a description that was identical apart from the replacement of warm with cold. The warm/cold trait turned out to be central in the sense of profoundly affecting the overall impression of the target person. When the list of traits contained warm, 91 per cent of judges guessed that the target person was also generous, compared with only 8 per cent when the list contained cold. When the stimulus list included warm, the target person tended to be perceived as also being happy, humorous, sociable, and popular, but when the stimulus list included cold, most judges thought the stimulus person would not have those traits but would be persistent, serious, and restrained. Other traits, such as reliable, were not significantly affected by the warm/cold trait. Other trait pairs, such as polite/blunt, do not produce the same centrality effect. Central traits are believed to have the property of centrality by virtue of being highly correlated with other traits in the judges' implicit personality theories. The phenomenon illustrates the property of a Gestalt in which the whole is more than the mere sum of its parts. See also halo effect.