Effects of Feedback and Stimulus Control on Pulse Transit Time Discrimination

The present study was designed to determine the effects of feedback on discrimination of pulse transit time (TT). Eighteen normotensive subjects were randomly assigned to one of three groups: (I) Random Feedback Control, (II) Contingent Feedback, and (III) Feedback plus Exteroceptive Cues. For each subject an ABBA within‐session design was used in which subjects compared TT to a predetermined mean approximately every 20 sec across four phases: a 10‐min baseline, followed by two 10‐min experimental phases, and a final 10‐min baseline phase. Results for discrimination accuracy indicated superior discrimination for subjects presented exteroceptive cues and/or feedback (Groups II and III). A decrement in performance was found for both Groups II and III during the final baseline phase, with slightly better maintenance for the feedback plus exteroceptive cues subjects. Measures of EMG, respiration, HR and vasomotor activity were obtained during training and were correlated with discrimination accuracy. Results showed that none of the physiological responses were reliably correlated with discriminative performance, and probably did not function as discriminative stimuli for TT discrimination.