The Waltzing Oddball


  • These data were collected in the laboratory of Clinical Psychology in Konstanz. Sincere thanks to Prof. Rudolf Cohen for providing that opportunity and for his helpful suggestions, to Gereon Hopmann and Gaby Arslan for their support, and to Marta Kutas for her many helpful suggestions on earlier versions of this paper.

Address requests for reprints to: Rolf Verleger, Neurologie, Medizinische Universität, Ratzeburger Allee 160, 2400 Lübeck, Germany.


We investigated whether task relevance and probability interact to influence P3 amplitude. High and low tones were presented in random order with equal probability. In the control condition (standard oddball), every high tone had to be counted. In the waltz condition, high tones had to be counted only if they were preceded by two other high tones. It was predicted that the P3s evoked by targets in the waltz condition would be larger than the P3s evoked by the same sequence of targets in the oddball condition. That is, the frequency of occurrence of the targets should have an effect on P3, in addition to effects of the frequency of stimulus occurrence and stimulus task relevance (target/nontarget). This prediction was upheld. However, the largest P3s were evoked by nontargets following two high tones in the waltz condition. These P3s had a more anterior topographic maximum than usual. We contend that these anterior P3s reflect the interruption of an ongoing task and cannot be easily fit into the framework of the two concepts of task relevance and probability.