Evaluation of the Extent of Somatic Marker Hypothesis

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Critically evaluate to what extent the ‘somatic-marker hypothesis’ explains how decisions are made in the face of an uncertain outcome.

In mind of Kim Sterelny’s (2007) statement that ‘Human Life is one long decision tree’, it is not surprising that there has been a vast amount of research into the process of how we evaluate the desirability of alternative choices and select a particular option. One area of research, of particular interest here, is Damasio’s Somatic Marker Hypothesis (SMH) (1991) which uses the neuroeconomic approach through its integration of the fields of psychology, neuroscience and economics to invoke an understanding of how one makes a decision (Damasio, Tranel & Damasio, 1998). This Theory supports the RAF hypothesis that significant risky outcomes elicit emotional reactions (Stanfey, Loewenstein, McClue & Cohen, 2006,). The SMH proposes that stochastic decision making is the result of emotion-based biasing signals in the body- in particular from the Ventromedial Prefrontal Cortex (VMPFC) (Bechara, Damasio, Tranel & Damasio, 2005). This concept will be discussed in further detail (with reference to it’s origin and experimental support), followed by a critical analysis of the extent to which the SMH successfully explains what it contends to. Since the SMH focuses solely on the role of emotion in decision making, the Rationale Planning Model (1995) will also be examined in comparison to the SMH for it’s explanation of decision making as a purely logical and rational process. The Rational Planning Model by Banfield (1995) proposes that the decision maker consciously undergoes five steps when coming to a decision and so approaches the choice in a very rational manner. Subsequently, an evaluation of the two theories for stochastic decision making will follow to discern how well they account for stochastic decision making.

The SMH stemmed from attempts to explain why a patient (E.V.R.), with an ablation of the VMPFC, often engaged in behaviors that were detrimental to his wellbeing (Damasio, 1996). Emotion was originally believed to be a disruptive force in decision making, but since the VMPFC is in charge of emotional function, it was now speculated to be essential for the ability to make a decision. Further investigation into this phenomenon through neuropsychological examination, found that those patients with damage to their VMPFC evinced a generally flat affect and an inability to respond to emotional situations (Bolla et al. 2003). Thus, Damasio extracted that the decision making deficits experienced by these patients was a result of this altered psychophysiological response (Damasio, 1996). His SMH contends that when presented with a decision, the normal brain will use the VMPFC to react emotionally to the situation and generate ‘somatic markers’ in order to come to a decision. A somatic marker is best defined as the brains construction of a physiological change that it apprehends for the selection of a particular strategy. It supposedly guides attention towards the more advantageous option (Dalgleish, 2004). This enables the organism to react quicker to external stimuli as it no longer needs to wait for the activity to emerge in the periphery before it can elicit a reaction (Dalgleish, 2004). Furthermore, the VMPFC is thought to support association learning between complex situations and the somatic changes usually experienced during a particular situation (Jameson, Hinson, & Whitney, 2004). Put simply, once a previous situation that elicited similar somatic markers is identified, the VMPFC can use past experiences to rapidly evaluate possible behavior responses. So when the VMPFC suffers impairment, the somatic marker system can no longer be activated, resulting in an absence of physiological feedback and an inability to predict long term punishments and rewards. This occurrence has been termed ‘Myopia for the future’, where a decision may only be formulated by the use of a...
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