Lec 5: Social Perception

Thin Slices of Nonverbal Behavior —> Ambady & Rosenthal (1992)

• what they did: untrained judges evaluated brief video or audio clips (under 5 minutes) of individuals' nonverbal behavior. These quick judgments were then compared against objective, real-world criterion measures, such as teacher ratings, sales figures, and clinical outcomes.

• findings: strong correlation between thin-slice judgments and actual real-world outcomes. Remarkably, observers who viewed clips lasting under 30 seconds were just as accurate as those observing 5-minute clips, and silent nonverbal channels were often as predictive as spoken content. the shorter the clips (30 vs 6 sec) were better at forming a more accurate judgement. Those who were assigned a cognitive task (ex: math problem) while watching the clips has a slightly lower r-value.

• what it means: demonstrate that humans possess a rapid, automatic cognitive ability to accurately judge social and behavioral traits through subtle, hard-to-fake nonverbal cues. Consequently, first impressions hold significant predictive value, allowing researchers and individuals to form reliable assessments from fleeting interactions.

Retinotopic mapping

adjacent points on the retina are represented by adjacent neurons in the cortical visual areas (v1), preserving the geometric layout of the visual field. Two spots next to each other in the world are processed by neurons that are next to each other in the brain.

How does visual information travel though the brain?

1) visual information enters through the eyes/retina and crosses over to the opposite hemisphere

2) arrives at the primary visual cortex (v1) in the back of the brain

3) slow process after as it makes its way back to the front of the brain

4) as it moves forward, the scene keeps being rebuilt, each time with more detail, color, and meaning.

Note: in. the v1 representation is just lines, angles, edge orientations, basic shading. It hasn’t been organized into objects and nothing in the v1 is consciously experienced.

Tell me about the two visual pathways

“Where” Pathway

• located in parietal cortex

• identifies WHERE things are in your field of view

“What" Pathway

• located in ventral temporal cortex

• identifies the THINGS in your vision field

• line orientation and edge detection

• view-dependent: responds to object form particular angle (ex: you see a person from a head-on angle and certain neurons respond. meanwhile, neighboring neurons respond to the same person but from a different angle. The different set of neurons don’t treat those views as the same entity.)

• view-invariant: responds to object from any angle (ex: knows its Matt regardless of the angle you see him form)

• as information moves along the what pathway from the back of brain to the front, it goes through view-dependent representation first then shifts to the view-invariant representation

Explain low and high spatial frequencies. How do other animals see the world?

• LSF: super fast & blurry

• HSF: high level detail like lines and edges but no shading. requires lots of cortical processing.

• Broad spatial frequencies (BSF) / normal vision = LSF + HSF

• animals mostly have LSF (ex: rats, goldfish, cats) b/c it requires lots of cortical processing but there’s animals like eagles who have 2x better vision than humans

Electrode study —> Mendez-Bertolo (2016)

• what they did: recorded electrical activity from brains of the patients using electrode strips placed on the surface of the fusiform gyrus and depth electrodes placed into the amygdala.

• findings: The fusiform gyrus had a large response of N170 regardless of expression and whether it was HSF/LSF/BSF. The amygdala showed a high response at around 250-300 milliseconds, consistent with the info traveling forward from the fusiform gyrus. However, at 20 milliseconds, the amygdala was already responding differently to fearful faces which was way too early to be consistent with the explanation of the back of the brain route. the early response was only triggered by LSF and HSF(because it contains LSF). HSF only affected amygdala at 300 milliseconds

• what it means: The fusiform gyrus does its job on all faces the same. The amygdala gets a blurry draft of the face and the detailed version much later.

process of social perception of fear

High road vs Low road

High road

• through visual cortex

• full detail

• amygdala at 300ms

• thamalus —> primary visual cortex (unconscious) —> fusiform gyrus —> amygdala

Low road

• thalamus straight to amygdala

• blurry gist

• 20-30ms

• helps respond quickly to potential threats

• thalamus —> amygdala

• unconscious

Amygdala

• almond-shaped structures tucked inside each temporal lobe

• has about 15 nuclei that each have a different function but they work together as an early warning system

• helps detect danger, respond to emotional faces, keep an appropriate distance from others

• responds to all emotions but more to fear

• sets physiological preparation in motion (flight or fight response)

why does the amygdala respond to fearful faces?

It is not because we are scared of fearful faces but rather because a fearful face may indicate something dangerous is nearby that they’ve seen but I can’t see it or haven’t noticed. This is also why the amygdala responds more to fearful faces that are not looking directly at you.

Nonconscious emotional processing —> Whalen (1998)

• when participants were shown fearful faces subliminally, the amygdala was immediately activated

• other subliminally presented faces did not trigger the amygdala

• low road is unconscious so it makes sense that the amygdala picks up on subliminal cues that our conscious self does not

• part if it may be because we evolved to pick up threat signals w/o conscious awareness so the body can start preparing before the full 300ms

Amygdala respond to emotional faces in cortically blind patient —> Pegna (2005)

• cortical blindness comes from damage to early visual cortex in back of the brain. people with this have no subjective experience of seeing

• yet when presented with a fearful face, the amygdala still responds but it doesn’t for the other emotions presented

• this means the information has to be traveling through low road since the visual cortex is damaged

No amygdala —> Adolphs (1999)

• what he did: compared people with bilateral amygdala damage to people with brain damage elsewhere and asked how accurately each group could identify emotional facial expressions.

• findings: ppl w/o amygdala recognized happy faces just as well as the controls and for several other emotions the difference was very little. However, the big difference was fear b/c they were terrible at recognizing it.

• what it means: although amygdala responds to many emotions, it seems to do something special for fear faces

people w/o amygdala also stand closer to people because normally if there’s someone in your “safe zone” it triggers a sense of threat, but that sense is missing w/o amygdala.

Does the amygdala generate the FEELING of being afraid?

No, evidence suggests it is more involved in recognizing fearful expressions, physiological preparation, and social behavior rather than involved with people’s subjective feelings of fear. Regions that are more tied to the subjective experience of fear and other emotions are: vmPFC, anterior insula, TPJ (tracks it the best)

Pareidolia effect

its so important to see faces that evolution “decided“ it be better to mistakenly see faces than to miss seeing a face when there is one