Augmenting–reducing paradox lost? A test of Davis et al.ʹs (1983) hypothesis

The aim of the experiment was to test Davis et al.ʹs [Davis, C., Cowles, M., & Kohn, P. (1983). Strength of the nervous system and augmenting–reducing: paradox lost. Personality and Individual Differences, 4, 491–498.] hypothesis, that Petrie-style reducers become evoked potential (EP) augmenters at high intensities. Central, autonomic, and subjective responses to auditory stimuli of five intensities from 65 to 105 dB(A) were recorded in subjects classified as augmenters/reducers according to the Vando reducer–augmenter scale (RAS). Forty-five white noise stimuli of each intensity were presented. EEG, ECG, EDA, subjective and behavioral data were recorded. It was hypothezised that augmenters would show a zero- or negative-slope of the evoked potential and a defensive-response pattern in peripheral-physiological variables at higher intensities whereas reducers would exhibit a positive slope and an orienting response pattern. In addition, the relationship between augmenting–reducing as assessed by the RAS and EP-method and Sensation Seeking was investigated. Contrary to expectation, reducers exhibited a lower reactivity than augmenters. This applied to the N1-P2-component as well as to the electrodermal response and partially also to the heart rate response. Reducers rated the noises as less loud and less uncomfortable compared with augmenters. Moreover, reducers scored higher on the sensation seeking scale, but there were no significant correlations between the EP-method and sensation seeking. Additionally, reducers responded faster in a reaction time task than augmenters. Overall, results indicate an enhanced reactivity of augmenters and a diminished reactivity of reducers thereby confirming the construct validity of the RAS.