Lapses in skin conductance responding across anatomical sites: Comparison of fingers, feet, forehead, and wrist.

The fingers are widely accepted as the gold standard for skin conductance (SC) recording, with the feet as a strong alternative. However, there are gaps in the current literature comparing these sites. There is also a great deal of interest in alternative recording sites to permit mobility, but data evaluating these are few and inconsistent. The present report compared multiple sites (fingers, abductor hallucis of the foot, arch of the foot, toes, forehead, and wrist) from 45 college student participants in a short-term sedentary laboratory setting and found large variation in both tonic and phasic SC responses, as well as crucial lapses in responding at nonpalmar sites. Across-site correlations between participants and within participants were also examined. The present data show that, in the laboratory setting employing commonly used recording techniques and stimuli, the nonpalmar sites are generally less responsive than the fingers, and the wrist in particular is the lowest in responding, whereas the toes are most similar to the fingers in responding. Within-participant correlations between the fingers and other sites were greatest for the plantar sites and least for the forehead.

Can you give me a hand? A comparison of hands and feet as optimal anatomical sites for skin conductance recording.

The fingers and feet have long been accepted as optimal anatomical recording sites for electrodermal activity. The available literature suggests that the feet are more responsive than the fingers. The present report compared skin conductance level (SCL) and responses (SCRs) from the left foot and the distal phalanges of the fingers on the nondominant hand among 19 participants. The principal results were (a) SCRs recorded from the fingers were significantly larger and more frequent with shorter latencies than SCRs from the foot, (b) SCL from the fingers was significantly higher than from the foot, (c) the fingers exhibited significantly greater discrimination conditioning than the foot, and (d) skin conductance measures recorded from the fingers and foot were significantly positively correlated. Specifically, our results demonstrate that the distal phalanges of the fingers are electrodermally more responsive than the abductor hallucis area of the foot.

Can human autonomic classical conditioning occur without contingency awareness? The critical importance of the trial sequence.

Most evidence suggests that awareness of the CS-US contingency is necessary for human autonomic conditioning. However, Schultz and Helmstetter (2010) reported unaware skin conductance conditioning using difficult-to-discriminate visual CSs. We sought to replicate these findings with procedures nearly identical to Schultz and Helmstetter among 66 participants. Results replicated the findings of significantly greater autonomic responding to CS+ than CS-; however, participants also demonstrated greater expectancy of shock to CS+ than CS- despite being classified as unaware. The differential expectancy and conditioning occurred only on trials that followed a CS+/CS- alternating sequence. On non-alternating trials, there was significantly higher expectancy and skin conductance responding to CS- compared to CS+. These results indicate that what initially appeared to be unaware differential conditioning was likely due to differential expectancy arising from a predictable trial sequence. These results underscore the critical importance of controlling for trial sequence effects in the study of learning.