The response bias inYES‐NOdetection with gated noise and simultaneously gated signal plus noise was found to show both sequential and probability contrast. The sequential dependencies showed that the more recent a signal event, the more the response bias shifts away fromYES. Similarly, the more probable the presentation of a signal, the more the response bias shifts away fromYES. The response bias in detection with continuous noise usually shows the opposite effect—response assimilation. The probability of aYESresponse increases with either greater signal probability or with signal recency. It is suggested that the response‐bias learning which has been postulated to occur in detection experiments depends on the stability of the judgmental frame of reference provided by the continuous noise. When this basis is removed, as in the present study, the response pattern parallels that usually observed in signal recognition studies for which responses are assumed to depend on the memory of the previous presentations. It is concluded that the response pattern, assimilation or contrast, depends more on the stability of the frame of reference than on the type of psychophysical task.