The core idea
Damasio observed that some patients with damage to the ventromedial prefrontal cortex retained normal intelligence but made poor personal and social decisions. He proposed that past experience links options to bodily responses, which later act as markers, biasing a person toward or away from a choice. These signals are thought to narrow the range of choices that must be reasoned through.
The Iowa Gambling Task
Bechara and colleagues developed a card game in which participants choose among decks that differ in long-term payoff. Patients with ventromedial damage tended to continue selecting from disadvantageous decks. Early reports stated that healthy participants developed skin conductance responses before risky choices, even before they could explain which decks were bad.
- Some decks offer high immediate gains but larger later losses
- Skin conductance served as an index of bodily arousal
Critiques
Maia and McClelland found that when participants were questioned in more detail, they displayed knowledge of the decks earlier than first thought, undermining the claim that bodily signals operate before awareness. Dunn, Dalgleish, and Lawrence reviewed the evidence and concluded that central claims lacked strong support. Patients' difficulties may also reflect problems with learning to reverse choices. Bodily feelings do seem to influence some decisions, but the specific causal role proposed has remained contested.
Further reading
- Bechara, A., Damasio, A. R., Damasio, H., & Anderson, S. W. (1994). Insensitivity to future consequences following damage to human prefrontal cortex. Cognition, 50(1-3).
- Maia, T. V., & McClelland, J. L. (2004). A reexamination of the evidence for the somatic marker hypothesis: What participants really know in the Iowa gambling task. Proceedings of the National Academy of Sciences, 101(45).
- Dunn, B. D., Dalgleish, T., & Lawrence, A. D. (2006). The somatic marker hypothesis: A critical evaluation. Neuroscience and Biobehavioral Reviews, 30(2).