Research gap at a glance
- Question: Does acute blockade of peripheral autonomic feedback in healthy people, or focal insula damage studied with bodily measures, degrade decision-making under ambiguity, and if so through loss of the bodily signal, loss of its perception, or something unrelated to the body?
- Why it matters: The somatic marker hypothesis predicts that removing the body loop should harm decisions under ambiguity. Existing patient tests may have missed this because patients had long-standing damage and could have adapted, and the lesion studies that do show deficits never measured the body, so the causal role of bodily feedback remains untested.
- Theme: Emotion and self
- Status: open
What the wiki already knows
- By 2005 four patient-group tests of peripheral feedback had been reported, and in aggregate they favour little peripheral impact on decision-making, but every group had long-standing damage and may have adapted onto the as-if loop (Dunn et al. (2006), Does somatic feedback guide decisions?).
- Dunn et al. proposed acute successors: the peripherally acting beta-blocker nadolol in healthy volunteers, patients with facial paralysis, and peripheral blockade within pure autonomic failure patients (Dunn et al. (2006)).
- Three lesion studies targeting the insula report a decision deficit, but none recorded anticipatory skin conductance, heart rate or any interoceptive measure, so the deficit fits loss of the signal, loss of its perception, or loss of an expected-value computation (Jones et al. (2010), Does somatic feedback guide decisions?).
- Whether ambiguity engages the body loop and certainty the as-if loop has not been tested on tasks matched for everything except epistemic character (Body loop and as-if body loop).
What would answer it
- A double-blind crossover in healthy volunteers comparing nadolol with placebo on ambiguity and risk versions of a card task matched in structure, with anticipatory Skin conductance response (SCR) and heart rate recorded per choice; and a lesion study comparing focal insula, focal ventromedial prefrontal and dorsolateral control groups on the same task with the same bodily measures and a cardiac accuracy task.
Connections
- Raised on: Does somatic feedback guide decisions?, Dunn et al. (2006), Body loop and as-if body loop, Jones et al. (2010)
- Related concepts: Somatic marker hypothesis, Body loop and as-if body loop, Insular cortex, Ventromedial prefrontal cortex (VM)
- Related debates: Does somatic feedback guide decisions?, parietal workspace?
Everitt’s experiment, testing decisions in people without peripheral feedback, was proposed decades ago and has since been run in several patient groups. Dunn et al. (2006) found the aggregate closer to Damasio’s 1996 expectation of little peripheral impact than to later claims. What remains open is the acute version, because every patient tested had lived with the damage for years and the hypothesis itself allows an as-if loop that simulates bodily states centrally (Body loop and as-if body loop).
The lesion evidence pulls the other way but without the needed measure. Damage to the insula, a core interoceptive structure, degrades risky choice, which looks like causal support. Yet Does somatic feedback guide decisions? points out that none of these studies recorded the body or measured interoception, so they cannot say why choice suffers. The design the debate page proposes combines Clark’s three-group lesion comparison with Dunn’s per-choice bodily-differentiation term.
The two designs are complementary. Pharmacological blockade removes the signal in otherwise healthy brains without time to adapt; the lesion design removes cortical processing while leaving the signal intact. If decisions suffer in the first case, bodily feedback matters; if only in the second, the deficit may lie in central computation. The same nadolol design is proposed for the ageing question on Does interoception decline with age because the signal fades or because perception does?.