Facilitation of heartbeat self-perception in a discrimination task with individual adjustment of the S+ delay values.

Thirty-two subjects (16 women, 16 men) performed two tasks that were the result of adapting the heartbeat perception tasks produced by Whitehead et al. [Biofeedback Self-Regul. 2 (1977) 371] and Katkin et al. [Psychophysiology 19 (1982) 568], respectively. In the Whitehead task, the delay values were the standard 128 ms for the S+ stimulus and 384 ms for the S- stimulus after the R-wave in one case; in the other case, the delay values were individually adjusted according to the median of the distribution of interval choices in an adaptation of the Brener and Kluvitse [Psychophysiology 25 (1988a) 554; Psychophysiology 25 (1988b) 436] task carried out previously. In the Katkin procedure, in one case S+ always occurred at a fixed interval (100 ms), whereas S- occurred at uniformly increasing intervals in relation to the R-wave. In the other case, the S+ and S- intervals were also individually modified according to the performance in the Brener and Kluvitse task. The results indicate that when the S+ values are individually adjusted, the sensitivity of subjects, as reflected in the 2(arcsin(p(A)(1/2))) values, significantly improves in the Whitehead task. Additionally, it was seen that the performance deteriorated from the first to the last 50 trials, especially when the S+ values were adjusted.