Validity of electrodermal activity-based measures of sympathetic nervous system activity from a wrist-worn device.

Measuring electrodermal activity (EDA) on the wrist with the use of dry electrodes is a promising method to help identify person-specific stressors during prolonged recordings in daily life. While the feasibility of this method has been demonstrated, detailed testing of validity of such ambulatory EDA is scarce. In a controlled laboratory study, we examine SCL and ns.SCR derived from wrist-based dry electrodes (Philips DTI) and palm-based wet electrodes (VU-AMS) in 112 healthy adults (57% females, mean age = 22.3, SD = 3.4) across 26 different conditions involving mental stressors or physical activities. Changes in these EDA measures were compared to changes in the Pre-ejection period (PEP) and stressor-induced changes in affect. Absolute SCL and ns.SCR frequency were lower at the wrist compared to the palm. Wrist-based ns.SCR and palm-based ns.SCR and SCL responded directionally consistent with our experimental manipulation of sympathetic nervous system (SNS) activity. Average within-subject correlations between palm-based and wrist-based EDA were significant but modest (r SCL = 0.31; r ns.SCR = 0.42). Changes in ns.SCR frequency at the palm (r = -0.44) and the wrist (r = -0.36) were correlated with changes in PEP. Both palm-based and wrist based EDA predicted changes in affect (6.5%-14.5%). Our data suggest that wrist-based ns.SCR frequency is a useful addition to the psychophysiologist's toolkit, at least for epidemiology-sized ambulatory studies of changes in sympathetic activity during daily life.

The short Sing-a-Song Stress Test: A practical and valid test of autonomic responses induced by social-evaluative stress.

The Sing-a-Song Stress Test (SSST) was recently developed as an alternative to the Trier Social Stress Test (TSST) to investigate autonomic nervous system responses to social-evaluative stress. In the SSST, participants are suddenly cued to sing a song in the presence of confederates. However, the SSST is still quite long (~15 min) and the requirement for confederates makes it labor-intensive. The current study tested whether a shorter (~6.5 min), single-experimenter, version of the SSST can still reliably elicit subjective and physiological stress reactivity. Our sample consisted of 87 healthy young adult participants (age range: 18-35 years). During the short SSST and a speeded reaction time task, in which aversive loud tones were to be avoided (TA), we measured heart period (HP), sympathetic nervous system (SNS) activity using pre-ejection-period (PEP), skin conductance level (SCL), and non-specific skin conductance responses (ns.SCR), and parasympathetic nervous system (PNS) activity using respiratory-sinus-arrhythmia (RSA) and the root-mean-square of successive differences (RMSSD). The short SSST induced significant decreases in positive affect and increases in negative affect. MANOVAs on the clusters of SNS and PNS variables showed that the short SSST elicited significant HP (-118.46 ms), PEP (-7.76 ms), SCL (+4.85 µS), ns.SCR (+8.42 peaks/min) and RMSSD (-14.67) reactivity. Affective, SNS, and PNS reactivity to the new SSST social-evaluative stress task were of comparable magnitude to that evoked by the TA mental stressor. We conclude that the short SSST is a valid and cost-effective task for large scaled studies to induce social-evaluative stress to a sufficient degree to evoke measurable changes in PNS and SNS activity and affective state.

Legibility of video-blended TV menus.

This article describes three experiments relating to the legibility of TV menus. Special emphasis is placed on the influence of a relatively new feature in TVs: the possibility to blend graphics and video. Three experiments are presented: one concentrating on the influences of blending level and video content; one concentrating on the influences of content and of colour combinations; and one concentrating on the influences of various font characteristics. The results are interpreted in terms of guidelines for blended TV menus.