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The ability of smell in humans is actually very good, as demonstrated by research conducted by Porter et al (2007). In this study, people were required to follow a trail of chocolate oil using only their noses, with their eyes and ears covered. The research revealed that human beings are proficient at performing and following scent trails, guided by their sense of smell. Moreover, humans are capable of discriminating more than a trillion smells.
Why do we look down on our ability to smell?
→ We find it hard to talk about smells and name them. Odors operate below the surface, affecting lower brain regions shared with other mammals and reptiles (limbic brain regions and even lower, regions that produce survival instincts). This bias might explain why we perceive smells as less important to us.
The smell brain: anatomy
→ The sense of smell is chemical, consisting of molecules.
→ Remarkable features include:
- Limbic overlap: a connection between emotions and odors, with many regions close together and overlapping. This makes smell memories highly emotional.
- Ipsilateral projection: smell information entering the brain on one side is processed on that same side, with no thalamic intermediary or delay.
- Feedback to the bulb: top-down modulation, learning, and plasticity, affecting the olfactory bulb, allowing us to rewire which smells we attend to.
Key features of the function of smell:
→ Metastudies have identified typical regions that are active in smell:
- Piriform cortex (PC): registers stimulus identity (what is this smell) and extends to the amygdala, targeting emotional relevance.
- Orbitofrontal cortex (OFC)
- Anterior insula (AI): encodes the affective property of the smell (whether we want to approach or avoid the smell).
Plasticity of olfaction: we can quickly learn the importance (and dangers) of smell, for example, the smell of gas.
Odor discrimination after conditioning:
→ Research by Li et al (2008) showed that when a stimulus (hand) was given a shock, the brain could update the importance of a particular smell in connection with that stimulus. Participants could distinguish between two stimuli (hands) even though both emitted the same odor, emphasizing the role of conditioning.
Smell functions:
- Approach/Avoid (for example, food)
- Detecting environmental hazards
- Social communication
Chemical communication: types of information we can smell:
- Neuro Identity (we are all different)
- Strong genetic components to body odor (monozygotic twins)
- The ability to smell illnesses
- Smelling ages, gender
- Smelling emotions
Experimental set-up:
→ In two conditions, the sender watched a horror movie and a nature documentary. The receiver was then exposed to the fear odor and neutral odor of the sender.
- Emotional expressions were measured.
→ The hypothesis was that there would be more sensory intake in the fear condition (evolutionary functional to detect threats).
What they found: Exposure to a fearful body odor elicits a fearful facial expression in the receiver. This process is called emotional contagion.
Senders' results:
→ Also, the higher the fear experience, the more molecules are emitted. However, over multiple trials, the molecules decrease.
Receivers' method (n=31, double blind, within subjects):
- Olfactometer presented 4 body odors randomly: neutral, low fear, medium fear, high fear.
- Tested in fMRI scanner
- Face morph task (FMT): classify emotion expressions morphed between disgust and fear: individually calibrated for a more sensitive task. Calibration of emotional expressions was done to create a more sensitive experiment.
Example of trial:
Validating FMT: a disgusting artificial sweat-like odor causes participants to see more disgust in morphed faces morphed between disgust and fear.
Fear odor-induced bias to see more fear in ambiguous faces. No quantitative effects:
→ This suggests that emotional information from smells and faces interact, changing our perception of the world.
Fear odor-induced physiological effects: nasal aperture:
Fearful odors open the nose, allowing for increased detection (evolutionarily functional to detect threats).
Fear odor-induced brain activity (vs. neutral) in social brain regions:
→ Different brain regions are active in response to fearful odors, particularly the left amygdala.
Finding pheromones needs a multidisciplinary approach.
Emotional disorders and smell:
1. Social anxiety disorder (SAD):
→ The startle reflexes to the smell of fear are higher in highly anxious subjects.
2. Autism spectrum disorder (ASD):
→ Individuals with ASD show altered responses to (social) smells/stimuli, like the smell of fear.
3. Psychopathy and smell:
→ The more psychopathic traits, the poorer the smell ability and the poorer the level of empathy. Less empathy has been linked to a lesser ability to smell.
Oxytocin: reduces the smell of fear effect:
→ Investigation by Maier et al (2018) explored whether oxytocin diminishes behavioral and neural responses to social chemosensory stress cues. Oxytocin was found to reduce activation in certain areas of the brain, such as the amygdala, the anterior cingulate cortex in females, and the hippocampus in males.
Urbach-Wiethe disease (UWD) and smell:
- Rare recessive genetic disorder (~400 reported cases since discovery in 1929)
- 1/4th in South Africa. Thought due to founder effect (Dutch, German settlers)
- Located on chromosome 1, extracellular matrix protein 1 (ECM1)
- Causes thickening of the skin, hoarse voice, (basolateral) amygdala damaged
- Typically can test only small samples, but marked effects:
→ Hyper reaction to innate fear stimuli, hypo reaction to learned fear
- Investigation of the smell of fear is an interesting subject for future research.
Summary:
- Social anxiety: increased fear odor response
- Autism spectrum disorder: altered fear response
- Psychopathy: instrumental odor response
- Oxytocin: buffered response to fear
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Subjective Measures:
- Emotional experience assessment
- Personality questionnaires (e.g., STAI/STAS, LSAS, EQ-SQ, BIS-BAS)
How to Use in SNS?
- Control variable
- Correlation with other measures
- Comparison across studies
Observational Measures:
- Frequency of behaviors
- Used in animal and infant studies
- Scoring and counting behaviors
- Camera usage (blinding, inter-rater reliability)
- Eye-tracking
Performance Measures:
- Speed, reaction time, accuracy
- IQ tests
- (Emotion) recognition tests
- Selective attention
- Implicit association test
- Stroop task
- Classical task
- Emotional task (interference of emotion)
- Facial fear stroop
Physiological Measures:
- Controlled by the brain and spinal cord
- (Electro)physiological methods
- Skin conductance
- Heart rate, respiration
- Electromyography (EMG)
Skin Conductance Response (SCR):
- Measures sweat gland reactivity
- Related to sympathetic arousal
Heart Rate:
- Declaration and acceleration
- Heart rate variability (HRV)
Electromyography (EMG):
- Measures muscle activity
- Mimicking facial expressions
- Startle potentiation (e.g., eye blink potentiation)
Electrophysiological Brain Imaging:
- Neuron structure: cell body, axon, dendrites
- Single-cell recordings for firing rate measurement
Electroencephalography (EEG):
- Measures neural activity in the cortex
- Frequency bands (e.g., delta waves, beta waves)
- Event-related potentials (ERPs)
Advantages/Disadvantages of ERP:
- Advantage: Excellent temporal resolution
- Disadvantage: Poor spatial resolution
Magnetic Resonance Imaging (MRI):
- Better for spatial resolution compared to ERP
- Relies on alignment of water molecules
- Functional MRI measures blood oxygenation
Advantages/Disadvantages of fMRI:
- Advantage: Good spatial resolution (voxel size as low as 1mm3)
- Disadvantage: Poor temporal resolution
Structural Imaging Methods:
- Diffusion Tensor Imaging (DTI) for mapping white matter microstructure
- Measures communication bundles
Brain Imaging Conclusion:
- MRI measures brain structure, connections, and activation location
- Event-related potentials for timing of activation
- Subcortical brain imaging with high temporal resolution not currently available
Lesion Methods:
- Reversed engineering to infer function by removing a region
- Techniques include chemo/optogenetics
- Human research relies on accidents, stroke, lobectomy, genetic disorders
Transcranial Magnetic Stimulation (TMS):
- Coil with electric current induces a magnetic field
- Focal, reversible, and movable
- Investigates time-course of cognitions
Advantages/Disadvantages of TMS:
- Advantage: Focal stimulation
- Disadvantage: Lack of good placebo condition
Conclusion of Imaging Methods of SNS:
- Different temporal and spatial resolutions and invasiveness
Knowledge Clips Part 2: Amygdala and Emotional Processing
Amygdala Structure:
- Part of the limbic system
- Studied as a single structure in humans
- Evolutionary changes in amygdala size (BLA vs. CeA)
Low and High Routes (LeDoux):
- Visual processing routes in threat
Amygdala Structure:
- Part of the limbic system
- Studied as a single structure in humans
- Evolutionary changes in amygdala size (BLA vs. CeA)
Low and High Routes (LeDoux):
- Visual processing routes in threat perception
- High route: Thalamus to visual cortex to amygdala
- Low route: Thalamus directly to amygdala for rapid fear response
Fearful White Eyes Experiment:
- Amygdala responds to fearful eyes unconsciously
- Urbach Wiethe disease impairs fear recognition
- Patient SM and South African patients show different responses due to specific amygdala damage
Amygdala and Threat Conditioning:
- Reactivity, attention, recognition, learning, memory, and regulation
- Amygdala's role beyond fear: emotionally intense stimuli, positive/negative experiences
Insula:
- Linked to disgust traditionally
- Also involved in taste, pain perception, and general bodily awareness
- Main node of the salience network
Reward System and Motivation:
- Midbrain, striatum, cortex involvement
- Dorsal striatum for motivated behavior and habit formation
- Ventral striatum (nucleus accumbens) for reward experience and anticipation
Orbitofrontal Cortex (OFC):
- Computes/predicts current reward value
- Activity correlates with transitions in reward value
- Importance in behavioral flexibility
Anterior Cingulate Cortex:
- Cognitive and affective parts for conflict monitoring
- Adjusts behavior and updates based on conflicts
Emotions and Decision Making: Traditional View:
- Emotional decision making for intuitive, fast decisions
- Rational decision making for calculated, slower decisions
- Somatic marker theory suggests combining emotional and rational elements for optimal decisions
Somatic Marker Theory (Damasio):
- Emotional and rational parts combined for decision-making
- Importance of ventromedial prefrontal cortex in updating behavior based on somatic signals
- Conflict between ratio and affect in morality dilemmas
Morality and Decision Making:
- Ventromedial prefrontal cortex damage leads to more utilitarian decisions
- Interplay between emotions and rationality in decision-making
- Criticisms of somatic marker theory but general acceptance of vmPFC's role in integrating affective and cognitive information for decision-making.
1. Multidisciplinary Approach:
- Sociology, psychology, neuroscience
- Martin Luther King's quote emphasizing the importance of diverse perspectives to understand prejudice.
2. Sociology:
- Study of social behavior, origins, development, organizations, networks, and institutions.
- Recognition of in-group favoritism and inherent prejudice.
3. (Social) Psychology:
- Explores individual thoughts, feelings, and behaviors.
- Examines phenomena like dehumanization to understand motivations and emotions underlying prejudice.
4. Neuroscience:
- Studies behavior by examining brain circuitry.
- Example: Oxytocin's role in bonding but also potential for reinforcing racist stereotypes.
- Social neuroscience aims to integrate biology, individual psychology, and group sociology.
5. The Social Brain: Modular or Non-Modular?
- Discussion on whether the social brain functions through specialized routines or a more integrated, non-modular approach.
- Consideration of the triune brain model, highlighting reptilian, mammalian, and primate brain components.
6. Evolution and the Triune Brain:
- Bigger brains influencing both social and non-social intelligence.
- Social intelligence hypothesis: Pressure to outwit peers leading to increased intelligence in non-social domains.
- Social and non-social cognition interdependent.
7. Brain Evolution:
- Triune brain model overview, highlighting reptilian, mammalian, and primate brain structures.
- Mirror neurons as a social mechanism for observational learning.
8. Mixed Mode of the Social Brain:
- Parts may be modular, module-like, or non-modular, depending on specific functions.
- Advocacy for a network approach rather than assigning discrete social functions to specific brain regions.
9. Electrical Connections and Neuromodulators:
- Action potentials for motion, more diffuse for emotion.
- Role of neurotransmitters (glutamate, GABA) and neuromodulators (norepinephrine, serotonin, dopamine) in emotion.
10. Autonomous Nervous System:
- Rest and digest vs. fight or flight balance.
- Hypothalamus regulation and its connection to emotional states.
11. Motivation and Emotion:
- Distinction between motivation (reward seeking and punishment avoidance) and emotion.
- Approach/avoidance actions and subjective liking/disliking.
12. Theories of Emotion:
- James-Lange, Cannon-Bard, Papez and Maclean, and Schachter & Singer models.
- Body and brain connection in emotional states.
13. Basic and Complex Emotions:
- Exploration of basic emotions (fear, happy) across cultures.
- Evolutionary perspective on emotions with dedicated neural substrates.
- Introduction of complex social emotions like guilt, pride, and jealousy.
1. Cognitive Model: Bruce & Young (1986) vs. Neurobiological Model: Haxby et al. (2000)
- Two models for recognizing faces, emphasizing cognitive and neurobiological aspects.
2. Occipital Face Area (OFA):
- Early perceptual analysis of faces.
- Strong fMRI activity in response to faces, sensitive to physical changes (e.g., haircut, skin color).
3. Fusiform Face Area (FFA):
- Recognizing known faces.
- Strong fMRI activity in response to faces, sensitive to identity changes.
4. OFA vs. FFA:
- OFA primarily active in physical change conditions.
- FFA primarily active in identity change conditions.
5. Superior Temporal Sulcus:
- Responds to changeable aspects of faces and bodies (e.g., eye gaze, motion).
- Stronger fMRI response to eye gaze relative to person identity.
6. Body Recognition:
- Importance of recognizing bodies for additional information beyond faces.
- Distinct brain regions for body recognition: extrastriate body area, fusiform body area, superior temporal sulcus.
7. Processes in Face and Body Interpretation:
- Three parallel routes for interpreting faces and bodies (Wood et al., 2016).
- Unconscious linking of visual processing with emotional response.
- Conscious inferring of emotional state based on prior experience.
- Sensorimotor stimulation for empathy and understanding.
8. Emotion System:
- Different emotions activate overlapping brain areas.
- Amygdala and middle occipital gyrus activated in all emotions.
9. Emotional Body Language:
- De Gelder's model highlighting rapid, unconscious perception and conscious, detailed perception of emotional body language.
10. Disorders of Face and Emotion Recognition:
- Prosopagnosia (face blindness): Impaired face recognition without affecting object recognition.
- Types: apperceptive (visual analysis deficit) and associative (linking face to identity impairment).
- Causes: damage to core face recognition network or white matter pathways.
11. Person Recognition Disorders:
- Inability to recognize familiar faces or use non-visual person-specific characteristics.
- Affects semantic integration, linked to damage in anterior temporal lobe.
12. False Recognition Disorders:
- Patients falsely recognize novel faces as familiar.
- Overreliance on category representation, not considering identity-specific characteristics.
- Linked to damage in prefrontal cortex.
13. Capgras Delusion:
- Belief that familiar people have been replaced by body doubles.
- Lack of emotional response despite correct visual recognition.
- Linked to damage in bilateral frontal, right limbic, and temporal regions affecting memory and reality perception.
Testosterone: hypothalamus - pituitary - gonads (HPG) axis:
→ Testosterone drives dominance behavior in a highly dynamic manner.
Challenge hypothesis:
- High testosterone for competition and challenge
- Low testosterone for parental care and social bonding
Testosterone works recursively: it can build up, and it can decline.
→ It motivates us to go into competition with others, and by going into competition, the testosterone goes up too. So it motivates, but it also goes up by the motivation itself.
→ But if you lose these competitions, the testosterone will go down, and the motivation will decline as well.
Cortisol: hypothalamus - pituitary - adrenal glands (HPA) axis
→ Cortisol is produced in response to stress (reactive threat system: amygdala - hypothalamus - autonomous nervous system)
Cortisol is an end product! → High cortisol is not the cause of stress but the result of stress.
→ Serves a homeostasis function.
→ Can also build up (promotes threat anticipation): it will help to focus your attention on stressors more strongly.
- When this happens, you can reach an excess point of cortisol = allostatic load (when cortisol is overloaded, you won’t be able to reach a point of homeostasis anymore, chronic overload of cortisol).
- Related to different types of diseases, like obesity, cardiovascular diseases, hypertension, etc.
Cortisol (HPA) versus testosterone (HPG): the HPA axis inhibits the HPG axis and thus testosterone production, on all its levels, and cortisol also inhibits the action of testosterone in the brain.
→ This balance helps explain how testosterone can contribute to dominance behaviors.
- For example, when testosterone is high, when in competition, it can inhibit cortisol. And also the other way around.
- The inhibition is not perfect; both hormones can be high or low at the same time as well.
Testosterone and social hierarchy:
- Social hierarchy favors the individual (higher individuals have, for example, more power, food, sex, more chance of surviving).
- It also favors the group (makes the group stronger, more food, in war situations they are stronger, etc.)
Hierarchy dynamics:
- Social aggression: forms and maintains social hierarchy
- Physical violence: causes damage or is symbolic (fight without harm)
- Displays of dominance:
→ Physical displays (without physical contact)
- Like having gorilla groups, the upper gorilla is dominant, shows that in his behavior (eye contact, for example).
→ Cultural displays
- Things like clothing in humans
→ Signaling behavior:
- Staring contest
Eye contact/staring contest:
- Social confrontation: prevents aggression (like a referee looking at a footballer in the eyes with a severe gaze, to make clear he must not show that kind of behavior again).
- Gaze aversion is a subordinate gesture
The (classical/emotional) stroop task compared to eye contact/gaze aversion studies:
→
Eye gaze detection:
- Natural behavior in humans. But in the animal kingdom, it’s often perceived as something threatening or as showing dominance.
- To improve or initiate dyadic communication
- Social interaction and affective bonding
Eye gaze varieties:
Eye gaze detection in babies:
- Newborns preferentially look at faces with direct gaze. They pay attention more to somebody who is looking directly at them.
- This is also associated with increased oxytocin levels in mothers (and fathers); this facilitates direct gaze → first development of social skills of babies
- 6+ months: babies can follow moving head and eyes, preference towards the eyes by the age of 2
The watching eye effect:
- We intuitively know when somebody is looking at us. So when you are sitting in class and you feel that someone is looking at you
→ this enhances prosocial behavior (for example, fewer bicycle thefts, less littering, higher donations). Just because of the feeling that someone/people are watching you
- It also increases self-awareness (larger Stroop effect > larger cognitive interference, thus a harder time processing visual information)
The gaze orienting effect: it is easier with eyes as a cue (directing you to the place of the target, so in a congruent trial) to watch to the correct side of the target.
→ it is situation dependent: larger gaze orienting effect with…
- Fearful, surprised, or dominant faces.
- When the face and object are both positive
- Under joint attention
→ it is also person-dependent:
- Females show a larger gaze orienting effect than males
- Younger people show a larger effect than older people
- Low-esteem people show a lower effect than high-esteem people
But there are also cultural effects:
→ in a study (Cohen et al. 2017) about the comparison of gaze cueing effects in European Americans and East Asians:
- Gaze cueing effect for individuals from East Asia disappears for mismatched conditions. But this was the case for the European Americans. So there seems to be a culturally specific effect, where individuals that come from a collectivistic-holistic society are more likely to show the gaze effect if it's embedded in a specific context where everyone is looking in the same direction.
- Cultural differences in social orientation: collectivistic-holistic vs. individualistic-analytical
Neural substrates of gaze perception:
Two different networks:
- Yellow: social processing
- Blue: gaze perception
→ they, of course, show overlap because a lot of gaze perception has to do with social processing, and the other way around.
Superior temporal gyrus:
- Gaze perception
- Sensitive to social attention cues
Medial prefrontal cortex:
- Joint attention
Right temporal parietal junction:
- Live face-to-face interaction (when we have direct interaction with somebody, instead of looking at pictures or recordings)
Neural substrates in infants:
→ fNIRS study
These clips focus on empathy, simulation theory, and autism.
Empathy: the ability to read the mind of others.
→ In daily life, we consider it to be a good thing.
When we talk about empathy, we talk about hypotheses or inferences we make about the mind of others.
→ But how do we even know that others have a mind? We cannot be sure that other people have the same feelings, thoughts, etc., as we do.
- Philosophical zombie problem (David Chalmers)
Daniel Dennett: intentional stance
- Zero order intentionality: we look at things without assuming that there are intentions there. For example, when we look at a rock laying on the ground.
- First order: we assume that another person has a mind
- Second-order: we assume that another person is making assumptions about the mind of others
- Third-order: where you assume that another person is assuming about the mind of others.
Empathy: Two explanations
1. Theory-theory: formal cognitive knowledge about mental states and behavior.
- Inferences about goals or emotions
- Fairly spontaneous
- Stem from an understanding of the situation
- Probe recognition task: [link to the task]
→ Sally Anne task (theory of mind): putting yourself in somebody else’s shoes. Really about cognitive empathy, about knowing what the other one knows
> If children are using a theory of mind, they will say that Sally is going to look in the basket (because that is where they think that Sally thinks the ball is). But if they cannot do that, and thus cannot distinguish between their own knowledge and the knowledge of another, they will say Sally is going to look in the box.
2. Simulation theory: we simulate what we perceive and experience mental states (of what the other person is feeling, believing, or intending to do).
- Empathy: useful for a doctor? → Doctors need to have empathy for their patients when talking to them, but for the doctors, it is also good to be able to switch the empathy off when they have to do surgery.
→ Experiment with empathy of pain: the patients watched an injection with a numb hand (not a painful condition) versus a real injection (painful condition). The participants had to rate the pain and unpleasantness of the pictures, while their brain activity was registered.
- The TPJ (temporal parietal junction): an important brain area involved in switching empathy on and off and an important area in taking different perspectives.
Simulation theory: we understand the emotions, behaviors, and intentions of others because we simulate what we see (De Waal & Preston).
→ Not only humans, but also other species have this simulating behavior.
Barrett (2017): core emotions/affect. We have a limited set of core emotions that we experience and can perceive in others.
→ Activation vs deactivation, and pleasant vs
What is a personality disorder?
A. An enduring pattern of inner experience and behavior that deviates markedly from the expectations of the individual's culture. This pattern is manifested in > 2 of the following areas:
- Cognition
- Affectivity
- Interpersonal functioning
- Impulse control
B. Inflexible and pervasive across a broad range of personal and social situations
C. Significant distress or impairment in social, occupational, or other important areas if functioning
D. Stable and long duration, and early onset (at least adolescence)
E. Not better explained by another mental disorder
F. Not attributable to a substance or another medical condition
The three P’s are important:
- Persistent
- Pervasive
- Pathological
→ Personality traits are diagnosed as a personality disorder only when they are inflexible, maladaptive, and persisting and cause significant functional impairment or subjective distress.
Personality disorders:
1. Cluster A:
- Paranoid personality disorder
- Schizoid personality disorder
- Schizotypal personality disorder
→ Individuals in this cluster often display odd or eccentric behavior, exhibit social withdrawal, and may have unusual beliefs or perceptual experiences.
2. Cluster B:
- Borderline personality disorder (instability in a range of things, more impulsivity)
- Narcissistic personality disorder
- Histrionic personality disorder (excessive emotionality and attention-seeking)
- Antisocial personality disorder (disregard and violation of the rights of others)
→ Individuals in this cluster tend to have dramatic, emotional or erratic behavior, often struggle with impulse control, and may have difficulty forming and maintaining relationships
3. Cluster C:
- Avoidant personality disorder
- Dependent personality disorder
- Obsessive-compulsive personality disorder
→ Individuals in this cluster typically exhibit anxious or fearful behavior, are preoccupied with fears of rejection or abandonment, and may have a strong need for control and perfectionism
How do personality disorders develop?
→ They arise from a complex interplay between genes, temperament, and environment
→ A significant number of BPD patients report experiences of sexual, physical, and/or emotional abuse.
- Meta-analysis showed that patients with BPD are over 13 times more likely to report childhood adversity (traumas) than non-clinical controls (particularly emotional abuse and neglect)
Schema therapy:
→ A schema is a framework through which we interpret certain things/events. The emotions, thoughts, behaviors, and bodily senses are colored by our schemas. Most of the time, you are not aware of your own schemas, but they have a lot of influence on your life and the way you experience things.
→ Events can trigger our schemas
An early maladaptive schema is’:
- A broad, pervasive theme or pattern
- Comprised of memories, emotions, cognitions, and bodily sensations
- Regarding oneself and one’s relationships with others
- Developed during childhood or adolescence
- Elaborated throughout one’s lifetime and dysfunctional to a certain degree
Core psychological needs (according to schema therapy):
- Secure attachments to others (includes safety, stability, nurturance, and acceptance)
- Autonomy, competence, and a sense of identity
The ability of smell in humans is actually very good, as demonstrated by research conducted by Porter et al (2007). In this study, people were required to follow a trail of chocolate oil using only their noses, with their eyes and ears covered. The research revealed that human beings are proficient at performing and following scent trails, guided by their sense of smell. Moreover, humans are capable of discriminating more than a trillion smells.
Why do we look down on our ability to smell?
→ We find it hard to talk about smells and name them. Odors operate below the surface, affecting lower brain regions shared with other mammals and reptiles (limbic brain regions and even lower, regions that produce survival instincts). This bias might explain why we perceive smells as less important to us.
The smell brain: anatomy
→ The sense of smell is chemical, consisting of molecules.
→ Remarkable features include:
- Limbic overlap: a connection between emotions and odors, with many regions close together and overlapping. This makes smell memories highly emotional.
- Ipsilateral projection: smell information entering the brain on one side is processed on that same side, with no thalamic intermediary or delay.
- Feedback to the bulb: top-down modulation, learning, and plasticity, affecting the olfactory bulb, allowing us to rewire which smells we attend to.
Key features of the function of smell:
→ Metastudies have identified typical regions that are active in smell:
- Piriform cortex (PC): registers stimulus identity (what is this smell) and extends to the amygdala, targeting emotional relevance.
- Orbitofrontal cortex (OFC)
- Anterior insula (AI): encodes the affective property of the smell (whether we want to approach or avoid the smell).
Plasticity of olfaction: we can quickly learn the importance (and dangers) of smell, for example, the smell of gas.
Odor discrimination after conditioning:
→ Research by Li et al (2008) showed that when a stimulus (hand) was given a shock, the brain could update the importance of a particular smell in connection with that stimulus. Participants could distinguish between two stimuli (hands) even though both emitted the same odor, emphasizing the role of conditioning.
Smell functions:
- Approach/Avoid (for example, food)
- Detecting environmental hazards
- Social communication
Chemical communication: types of information we can smell:
- Neuro Identity (we are all different)
- Strong genetic components to body odor (monozygotic twins)
- The ability to smell illnesses
- Smelling ages, gender
- Smelling emotions
Experimental set-up:
→ In two conditions, the sender watched a horror movie and a nature documentary. The receiver was then exposed to the fear odor and neutral odor of the sender.
- Emotional expressions were measured.
→ The hypothesis was that there would be more sensory intake in the fear condition (evolutionary functional to detect threats).
What they found: Exposure to a fearful body odor
The ultimatum game is an economic exchange between two people designed to measure fairness. While an economic perspective suggests human behavior is focused on personal gain, experiments, including the ultimatum game, reveal a more complex reality.
Prospect theory, based on experiments by Kahneman & Amos (1979), highlights the role of subjective experience in economic behavior. Loss aversion, where people have stronger emotional reactions to losing than gaining similar things, indicates a conservative and risk-averse nature. The ultimatum game involves a proposer and a responder, an extension of the dictator game with the option to reject.
Rejection in the ultimatum game is irrational and costly for both the proposer and responder. People consistently reject 30/70% offers and lower, showing aversion to inequity or unfairness. Two motivations for rejection include emotional commitment (anger/frustration/envy) and social preferences, aiming to restore equity and reciprocity through altruistic punishment.
The ultimatum game can be played in a single or repeated version, allowing the responder to signal dissatisfaction with proposals in the hope of a fairer outcome. Rejection, a form of altruistic punishment, is not stronger in kidney donors (true altruists) and is related to self-reported altruism.
Emotional and social components of rejection are explored through neuroscientific research. Activation of brain regions like dIPFC, Insula, and dACC in response to human unfairness suggests a social and emotional component. However, studies like Civai et al. (2010) indicate that rejection may not always be driven by arousal but rather by social value orientation (prosocial vs. proself).
In summary:
- Ultimatum game research shows emotional responses to unfairness.
- Punishment of unfairness occurs at a cost to oneself.
- Subjective emotion, rather than arousal, seems related to the rejection of unfairness.
- Prosocial value orientation may be the main motivational drive for costly punishment.
Altruism and Prosociality:
Altruism, doing something at the cost of oneself to help another, prompts the question of whether true altruism exists. Evolutionary arguments suggest sexual selection, kin selection, direct reciprocity (tit-for-tat), and indirect reciprocity (building reputation) as underlying factors.
In the trust game, an economic exchange to measure trust, participants typically invest and return percentages. Direct and repeated trust games explore building reputation and the adjustment of behavior based on social value orientation. Amygdala damage research reveals that individuals with damaged basolateral amygdala (BLA) are more generous, as they do not adjust their behavior based on the behavior of others.
Under perceived and real-time pressure, people become more prosocial, mimicking the effect of BLA damage. Emotion-driven altruism is emphasized in neuroscientific research, showing the joy of giving activates the striatum, subjective experiences activate the insula, and empathic behaviors involve the mPFC and TPJ.
In sum:
- Evolutionary theories emphasize the personal gain of prosocial behavior.
- Neuroscience favors an emotion-driven inherent drive for prosocial behavior.
- The interplay of biology and evolution suggests both cynics and believers may have valid points.
Live Lecture: Part 1 - Olfactory Social Neuroscience
Smell loss is inversely associated with color vision emergence, suggesting a trade-off between these sensory abilities. Humans, however, can outperform some animals in olfaction, but a certain level of olfactory strength is needed to be detected by humans.
The olfactory processing pathway involves the olfactory bulb, piriform cortex, and orbitofrontal cortex. The piriform cortex exhibits ensemble coding for odor identification, creating different maps of activity for various smells.
Smell serves functions such as judging edibility, avoiding environmental hazards, and social communication. Olfactory cues can convey identity, sickness, or diseases. Sickness affects attractiveness and liking, as observed in studies injecting individuals with saline or lipopolysaccharide (LPS).
The smell of fear is examined through individuals with a genetic variance related to body odor. The ABCC11 gene mutation results in almost odorless individuals. Fear-induced experiments show increased signs of fear and higher skin conductance responses.
Emotional contagion in receivers indicates the ability to detect fear odor. Chemical analysis reveals consistent molecules in the smell of fear, with hexadecanoic acid identified as a potential biomarker.
Possible neural mechanisms in the smell of fear involve connections between the olfactory bulb, piriform cortex, and amygdala, suggesting learned connections between odors.
Urbach-Wiethe disease (UWD) and smell research explore reactions to innate and learned fear, providing insights into the neural mechanisms of smell.
Part 2: Social Preferences or Emotion - Irrational Rejection of Unfair Offers
Homo economicus, from an economic perspective, focuses on personal gain. However, humans exhibit sensitivity to equity and inequity, willing to punish unfairness at a cost to themselves.
The ultimatum game (UG) and impunity game (IG) are explored, with the latter indicating rejection of unfairness even without punishment. The study aims to test whether emotion predicts rejection in IG and UG, focusing on real proposer/responder behavior.
Hypotheses from social preferences and emotional commitment accounts are tested, analyzing rejection rates, social value orientation, anger, subjective emotion measures, facial EMG, EEG, and frontal negativity ERP.
Results indicate that rejection rates are lower in IG than UG, supporting social preferences. Prosocialness and anger influence rejection more in UG than IG. Facial EMG and ERP data suggest that MFN (medial frontal negativity) predicts rejection in UG, particularly for prosocial individuals.
Conclusion: The data supports the social preferences account, highlighting the role of social value orientation and expectancy in rejection behavior. The study has limitations, including low data for IG analysis and missing SCR data.
Attachment Across Species:
Attachment is a long-lasting social bond found across animal species, especially in humans, involving romantic partners and infant-parent relationships. The goal of attachment is to maintain close proximity to the partner, both physically and psychologically/emotionally, with the aim of providing comfort and security.
Infant Attachment Styles:
The strange situation test assesses how children respond to strangers in the presence of their mothers, revealing different attachment styles:
1. **Securely attached:** Proximity seeking and moderate distress after separation, with the mother appropriately responding to the infant's signals.
2. **Insecure/avoidant:** Ambivalent behavior toward the mother, unclear and inconsistent in seeking proximity, often associated with neglectful maternal behavior.
3. **Insecure/anxious:** Proximity seeking and high distress after separation, associated with inconsistent maternal behavior.
(Infant) Attachment Styles in the Brain:
A study of 50 young adults determined attachment styles during infancy, childhood, and young adulthood. The study found two key findings:
- **Self > Other:** More activation in ACC, thalamus, midbrain, subcortex, cerebellum, brain regions active in romantic partner interactions and human affect/reward.
- **Infancy > Childhood > Early Adulthood (Time Factor):** More activation in occipital regions, temporal lobe, parietal cortex, and limbic regions during infancy, decreasing with age.
Additionally, higher ACC activity during interactions with the mother correlated with more child initiation of social communication, positive affect, warmth, motivation, and involvement, emphasizing ACC's role in representations of attachment, emotional processing, and social functions.
Consequences of Deprivation:
Using Romanian orphanages as an example, children faced malnourishment, limited social contact, and caregiving, leading to persistent neurodevelopmental disorders. A study compared Romanian and British individuals adopted in their first weeks of life, showing significantly lower brain volume and volume reductions in emotional processing regions among deprived individuals.
Take-Home Messages:
- Long-lasting social bonds involve different attachment styles.
- Attachment styles correlate with functional brain responses in adulthood.
- Childhood deprivation can have lasting behavioral and structural effects.
Adult Attachment:
Similar to infant attachment styles, adult attachment is often self-reported. Studies, such as Vrticka et al. (2008) and DeWall et al. (2012), explore neural responses based on attachment styles.
In the social support condition, higher self-reported avoidance attachment correlated with decreased activation in the ventral striatum and ventral tegmental area, suggesting that avoidant individuals show reduced activation of affective processes.
In the social punishment condition, higher anxious attachment correlated with increased activity in the left amygdala, indicating enhanced processing of situations associated with emotional arousal and fear for those with higher anxious attachment.
A study by DeWall et al. (2012) revealed positive correlations between anxious attachment and activity in the dorsal ACC and anterior insula, indicating greater negative responses to imagined social rejection and interpersonal conflict. On the other hand, avoidant attachment showed negative correlations with the activity in dACC and anterior insula, suggesting lower activity in attachment-relevant experiences.
Take-Home Messages:
- Adult attachment mirrors infant attachment.
- Attachment styles link to variations in
The Self Concept:
The self-concept involves self-referential processing, with different aspects:
1. **Sensorimotor self:** Includes a sense of agency and embodiment.
2. **Ongoing self:** Encompasses personality traits, motivation for self-esteem, and personal memories.
3. **Cultural/collective self:** Involves group membership, shared beliefs, skills, and rituals.
Personal vs. Social Identity:
- **Personal identity:** Identifying as an individual, influenced by motivations and self-esteem maintenance.
- **Social identity:** Identifying as a group member based on commonalities and positive social distinctiveness. People strive for a positive sense of self in both personal and social identity.
Better-Than-Average-Effect:
People tend to think more positively about themselves than the average of the group, serving self-enhancement and contributing to a positive self-view.
Self-Referential Processing and mPFC Activation:
Self-referential processing involves activation in the medial prefrontal cortex (mPFC). Studies show that mPFC activation facilitates self-judgment tasks, suggesting its role in self-referential processing.
Cultural Effects on Self-Referential Processing:
Cultural effects influence self-referential processing, as observed in studies where Chinese participants showed more activation for the "mother" condition, reflecting a collective-oriented interdependent culture, while Westerners exhibited self-judgment regardless of the closeness of the other person.
Social Identity:
Social identity involves social categorization, social identification, and social comparison, aiming to maintain a positive self-concept and social identity. Individuals strive for positive self-concept and social identity simultaneously.
Social Categorization:
Social categorization includes quick attentional processing (N1 and P2) with greater peaks for outgroup members. Deeper processing (N2) shows heightened responses for ingroup members. Ingroup identification influences social categorization, as evidenced in ERP studies.
Importance of Morality for Social Identity:
A study with an implicit association task revealed that emphasizing moral values reduced social bias towards the outgroup, suggesting a connection between moral values, social categorization, and bias.
Ingroup Preference and Group Dynamics:
Ingroup preference was studied in mixed-race groups, showing rapid categorization of ingroup faces. Likability for team members was enhanced in the ingroup condition, reflecting activity in brain regions like the fusiform face area, amygdala, orbitofrontal cortex, and striatum.
Criticism and Social Bias:
Studies on criticism (moral vs. competence) indicated increased attention to ingroup feedback, with greater activation in the ventral tegmental area and enhanced categorization in the N200 for participants highly identifying with the ingroup.
About Love
Triangular Theory of Love (Sternberg, 1988):
Perfect love involves passion, intimacy, and commitment, but these factors rarely align perfectly in real life.
Evolutionary Origins, Endocrine Factors, and Neural Correlates of Love:
Love's stages have evolutionary origins, endocrine factors like oxytocin and vasopressin, and neural correlates. Prairie voles' monogamous behavior is linked to oxytocin and vasopressin receptors, emphasizing the role of these hormones.
Long-Term Relationships and Neural Correlates:
Long-term relationships show enhanced activation in reward-related brain areas like the ventral tegmental area and nucleus accumbens. The frequency of sexual activity correlates with higher brain activation.
Grief and Neural Correlates:
Complicated grief involves distinct brain activation patterns, including heightened nucleus accumbens activity in
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