The Somatic Marker Hypothesis: Human Emotions in Decision-Making

Transcription

1 The Somatic Marker Hypothesis: Human Emotions in Decision-Making Presented by Lin Xiao Brain and Creativity Institute University of Southern California

2 Most of us are taught from early on that : -logical, rational calculation forms the basis of sound decisions. -Emotion has no IQ. -Emotion can only cloud the mind and interfere with good judgment. But what if we were wrong?! What if sound, rational decision making in fact depends on prior accurate emotional processing?

3 I will make the case that: Decision-making is a process critically dependent on neural systems important for the processing of emotions. Conscious knowledge alone is not sufficient for making advantageous decisions. Emotion is not always beneficial to decision-making; sometimes it can be disruptive.

4 A Brief History Phineas Gage was a dynamite worker, and survived an explosion that blasted an iron-tamping bar through the front of his head.

5 A Brief History Before the accident, Phineas Gage was a man of normal intelligence, responsible, sociable, and popular among peers and friends. He survived this accident with normal intelligence, memory, speech, sensation, and movement. However, his behavior changed completely: He became irresponsible and untrustworthy. Impatient of restraint or advice when it conflicted with his desires.

6 A Brief History

7 Patients with Ventral Medial/Orbital Prefrontal Cortex damaged

8 Patients with Ventral Medial/Orbital Prefrontal Cortex damaged Before brain damage: Normal intelligence. After the damage: Normal intelligence. But Difficulties making good decisions in real-life. Their choices are no longer advantageous, and are remarkably different from the kinds of choices they are known to make in the premorbid period: Their decisions and actions often lead to losses of diverse order, including: -losses in financial status-bankruptcies. -losses in social standing-involvement with unscrupulous people. -Break-up of family and distancing from friends.

9 Patients with Ventral Medial/Orbital Prefrontal Cortex damaged This particular class of patients presented a puzzling defect: difficult to explain their disturbances in terms of defects in knowledge, general intellectual compromise, language comprehension or expression, or in memory or attention. However, their ability to express emotion and to experience feelings in appropriate social situations becomes compromised. Along with normal intellect, these patients show: 1. Abnormalities in emotion and feeling. 2. Severe impairments in judgment and decisionmaking in real-life.

10 Somatic Marker Hypothesis (SMH) Especially this latter observation was what led Antonio R. Damasio to propose what has become an influential neural theory of decision-making, the Somatic Marker Hypothesis (SMH). The central feature of this theory is that emotionrelated signals (somatic markers) assist cognitive processes in implementing decisions. A further aspect of this theory is that these somatic markers can be non-conscious: they can bias behavior even when a person is not really aware of them.

11 Somatic Marker Hypothesis (SMH) Definitions: EMOTION as a collection of physiological changes in body and brain states triggered in response to an event: Some changes are non-perceptible to an external observer, e.g., heart rate, skin conductance, endocrine release. Some changes are perceptible to an external observer (e.g. skin color, body posture, facial expression). The signals generated by these changes towards the brain itself produce changes perceptible to the individual and are ultimately perceived as a FEELING. Emotion= What an outside observer can see, or at least can measure. Feeling= What the individual senses or subjectively reports.

12 Testing the Somatic Marker Model: -The Iowa Gambling Task (IGT) paradigm for measuring decision-making.

13 Iowa Gambling Task (IGT)

14 Iowa Gambling Task (IGT)

15 Iowa Gambling Task (IGT)

16 (a) The Iowa Gambling Task (IGT) Bad Decks Good Decks A B C D Gain per Card $100 $100 $ 50 $ 50 Loss per 10 Cards $1250 $1250 $250 $250 Net per 10 Cards -$250 -$250 +$250 +$250 (b) Skin Conductance Response (SCR) ANTICIPATORY SCR (Before Choice) REWARD/ PUNISHMENT SCR (After Choice) Onset of Card Selection 5 sec

17 Bechara A, 1994

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19 Card Selection Card Selection Card Selection Anticipatory Anticipatory R/P R/P R/P 0 second 10 second 20 second

20 Do these somatic (emotional) signals have to be conscious? No! 1. Somatic signals may bias decisions covertly. 2. Conscious knowledge alone is not sufficient for making advantageous decisions.

21 A Diagrammatic Summary of the Results of Bechara et al. (1997) Study (a) Knowledge Level (b) Anticipatory SCR Level Bad Decks Good Decks (d) Bad Decks Good Decks (c) (e) Number of Choices From Decks Sequence of Card Selection Controls Did not Reach Conceptual Period VMPC Did Reach Conceptual Period

22 Anticipatory SCRs represent unconscious biases that are linked to prior experiences with reward and punishment. Deprived of these biases, conscious knowledge of what is right and what is wrong may become available. However, by itself, this conscious knowledge is not sufficient to ensure an advantageous behavior. Therefore, frontal patients may be fully aware of what is right and what is wrong, but they fail to act accordingly: These patients can say the right thing, but they do the wrong thing.

23 Modulating Factors

24 1.Time: information conveying immediacy (e.g. getting a heart disease tomorrow) exerts a stronger influence on decisions than information conveying delayed/future outcomes (e.g. getting a heart disease 20 years from now). 2.Probability: people prefer a sure gain over a probabilistic one, or they avoid a sure loss and prefer a probabilistic one instead. 3.Tangibility: people have an easier time spending money on credit cards as opposed to spending real money.

25 Reflective Orbitofrontal /Ventromedial System Feedback: Net Positive or Negative Somatic State immediate high high concrete Time Frequency Magnitude Relation delayed low low abstract Triggering somatic states Strong Weak Impulsive Amygdala System + - Summation: Strong dominates Weak Information conveying immediacy (near future), high probability (certainty), or tangibility engages more posterior VMPC, whereas information conveying delay (distant future), low probability, or abstractness engages more anterior VMPC cortices (Bechara, 2005).

26 Reflective Orbitofrontal /Ventromedial System Feedback: Net Positive or Negative Somatic State immediate high high concrete Time Frequency Magnitude Relation delayed low low abstract Triggering somatic states Strong Weak Impulsive Amygdala System + - Summation: Strong dominates Weak The more posterior areas of the VMPC (e.g. Brodmann area 25) are directly connected to brain structures involved in triggering or representing somatic states, while access of more anterior areas is poly-synaptic and indirect.

27 Reflective Orbitofrontal /Ventromedial System Feedback: Net Positive or Negative Somatic State immediate high high concrete Time Frequency Magnitude Relation delayed low low abstract Triggering somatic states Strong Weak Impulsive Amygdala System + - Summation: Strong dominates Weak It follows that coupling of information to representations of somatic states via posterior VMPC is associated with relatively fast, effortless, and strong somatic signals, while the signaling via more anterior VMPC is relatively slow, effortful, and weak.

28 Reflective Orbitofrontal /Ventromedial System Feedback: Net Positive or Negative Somatic State immediate high high concrete Time Frequency Magnitude Relation delayed low low abstract Triggering somatic states Strong Weak Impulsive Amygdala System + - Summation: Strong dominates Weak The nearer, more certain or more tangible events possess stronger emotions/affects, and things that are far more distant in the future, far less probable, and far more abstract trigger much weaker responses.

29 1.Time: information conveying immediacy (e.g. getting a heart disease tomorrow) exerts a stronger influence on decisions than information conveying delayed outcomes (e.g. getting a heart disease 20 years from now). 2.Probability: people prefer a sure gain over a probabilistic one, or they avoid a sure loss and prefer a probabilistic one instead. 3.Tangibility: people have an easier time spending money on credit cards as opposed to spending real money.

30 The Neuroanatomy of Emotions and Feelings

31 The Iowa Gambling Task in fmri Images From Li X, et al., (Submitted)

32 Is Emotion Always Beneficial to Decision-Making? No! Emotion can be disruptive to decision-making.

33 Risky Decision-making Task Each participant was endowed with $20 of play money, which they were told to treat as real because they would cash the amount they were left with at the end of the study. Participants were told that they would be making several rounds of investment decisions, and that, in each round, they had to make a decision between two options: invest $1 or not invest. If the decision were not to invest, the task would advance to the next round. If the decision were to invest, they would hand over a dollar bill to the experimenter. The experimenter would then toss a coin in plain view of the subject. If the outcome of the toss was heads (50% chance), they would lose the $1 that was invested; if the outcome of the toss was tails (50% chance), $2.50 would be added to the participant s account. The task would then advance to the next round.

34 Risky Decision-making Task The task consisted of 20 rounds of investment decisions. The investment task was designed so that it would behoove participants to invest in all the 20 rounds because the expected value on each round is higher if one invests ($1.25) than if one does not ($1).

35 Shiv B, 2005

36 Shiv B, 2005 Emotional reactions to the outcomes on preceding rounds affected decisions on subsequent rounds for normal participants and control patients, but not for target patients

37 Emotions play a major role in the interaction between environmental conditions and human decision processes, with neural systems carrying emotional signals providing valuable implicit or explicit knowledge for making fast and often advantageous decisions. But sometimes, these emotional signals interfere with rational decisions. Thus it is not a simple issue of emotions are good or bad. It is a matter of discovering the circumstances in which emotions can be useful or disruptive, and using the reasoned coupling of circumstances and emotions as a guide to human decisions.

38 Knowledge Cognition Decisions Actions Affect Emotion Feelings The process of decision-making is not just logical and computational but also emotional.

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41 a. b. c. Reflective Impulsive DLPC AC Striatum Insula Immediacy Delay VMPC A Hyp DA 5-HT During the process of weighing somatic responses, the immediate and future prospects of an option may trigger numerous somatic responses that conflict with each other. The end result is that an overall positive or negative somatic state emerges.

42 a. b. c. Reflective Impulsive DLPC AC Striatum Insula Immediacy Delay VMPC A Hyp DA 5-HT Mechanisms that determine the nature of this overall somatic state (i.e., being positive or negative) are consistent with the principles of natural selection, i.e., survival of the fittest (Bechara & Damasio, 2005).

43 a. b. c. Reflective Impulsive DLPC AC Striatum Insula Immediacy Delay VMPC A Hyp DA 5-HT In other words, numerous and often conflicting somatic states may be triggered at the same time, but stronger ones gain selective advantage over weaker ones

44 a. b. c. Reflective Impulsive DLPC AC Striatum Insula Immediacy Delay VMPC A Hyp DA 5-HT The final decision is determined by the relative strengths of the pain/pleasure signals triggered by immediate and future prospects.