Cogn & perception: chem senses (smell) w3

Smell fucntions

• warns of danger

• Makes food taste better

• Identification of disease, gender

• Sexual communication?

Smell and disease

• smell nail polish breath diabetic

• Foul smell of lung absess

• stale beer stench of scrofula

• baked bread odor of typhoid fever

• windex smell of liver failure

Smell and taste Mozel 1969

• percentage of ppl who can identify food by smell

• High on coffee, lemon, whiskey

• sugar water was lower

• chocolate pretty high too

• lemon pretty high

• garlic lower

Reognition by smell

• better idetnification of food by taste. Enhances taste of food

• Women outweigh men in smell. Out of stimuli tested, 65 women were better, 15 men were better

The olfactory pathways

• taken in in olfactory mucosa at base of the brain. Cilia of olfactory receptor cells take in.

nose —) olfactory mucosa (cilia —) olfactory receptor cell —) axons —) neuron) —) olfactory bulb

Rhineencephalon (nose brain)

• olfactory bulbs (coding of odour)

• Amygdala (emotional)

• Hippcampus (memory)

The olfactory pathway process

Nose —› olfactory bulb —› hypothalamus —› pituitary gland —› reproductive organs

The olfactory pathways

• short links between incoming olfactory info and hippocampus —) olfaction in memory

• olfactory info and pituitary gland —) reproductive behaviour

The Proust Effect

• smell very good at evoking memory. long lasting in time and place

Smell and memory (Shepard 1967 + Engen & Ross 1973)

• Pictures - clear retention, correct recognition detailed at first, but quickly drops off

• less accurate recognition, but stays for longer with smell

Otherrr

• Inuit - rub noses, rub palms

• Certain indian languages ”kiss” meaning - request for a kiss = please smell me

• Europeans, cheek kisses

Pheromones (bringer of excitement in greek)

• chemicals used in animals for communication

• Dispersers - mark territory

• Aggregators - sexual attractors (pigs, moths, deer)

Pig on a truffle hunt (Dorries et al 1996)

• pheromones in male pigs. Used for truffle hunt

• Female pig for threshold for androstenone is 5-fold lower than make

Human pheromones??

• Apocrine glands produce steroids (androstenes)

• Forehead, nose, lips, ear lobes, genitals etc

• Do we detect pheromones? Not sure

• Are body odours important? Yes

• produced on puberty and onward

Sweaty vest study (1976 Russell)

• wear clean white shirt, shower with non perfume soap, not eat spicy foods, no aftershave etc

• Had ppl identify own vest vs others, male vs female

• Women better at it

Mentrual cycle synchrony (1971)

• 11 female subjects (6 dropped out)

• 1 female donor

• 4-5 synchronised with donor female subject

Why do we mask our odour with perfume?

• many perfumes use other animal pheromones

• - civetone - anal glands of civets

• - musk - anal glands of male musk deer

who knows?? the slides sure as heck not and my notes sure as heck not

Milinski & Wedekind (2001)

• 137 subjects into 3 immune system types

• Tested preferences in perrfumes

• Rose, civet, vanilla, bergamot, etc…

• There is a correlation between immune type

• ppl choose their perfumes to complement their body smell and to advertise their genes

Body odour for distinguishing…?

• can distinguish genders, family etc

• self from others

• women prefer the scent of men with a different immune system (sounds heteronormative but okay)

Perception of colour - what is it for?

• SCENE SEGMENTATION colour aid distinguishing different environments and arguemnts

• CAMOUFLAGE Different animals that may camoflage

• PERCEPTUAL ORGANISATION ,illustrate powerr of color in grouping

How do we perceive colour?

• The colour isnt in our external environment itself, its about how we perceive it

• Will we all perceive red the same?

Dimesion of colour

• wavelength —› hue or colour

• Intensity —› brightness

• Mixture —› saturation

Colour tree

• hue (around)

• Saturation (radius)

• Brightness (up and down)

After image

• eyes have 3 colour receptors (blue red green)

• Staring at the image, fatiguing different cones

• Ex: purple grass - red and blue are fatigued. Green isn’t fatigued and is cleared

• May not always see it bc it must fit just right on the retina of the old image

Neurons habituate - not continually processing same stimuli bc tiring. Happens in touch as well (aren’t thinking about how your clothes are touching you all the time)

Trichromatic colour theory or Yong Helmholtz theory

IMPORTANT FOR MCQ!!

• the combined responses of 3 receptors give rise to the perception of all colours

evidence:

• any colour can be made up by an additive mixture (mixing lights) of 3 primary colours

• Three cone types in retina

• There are types of colour blindness where 1 cone type is missing

• Computer use colour mixing on screens (old ones)

• Pointillism (painting made up of tiny dots)

• 3 diff wavelengths that the cones take in

but why do we experience after images?

Opponent process theory (Hering)

2 opponent processes

• red green, blue yellow, black white

• one fatigued, the other dominates. it’s a scale between one dimension or the other

Evidnce:

• there is no reddish green, No bluish yellow

• Common colour blindness is red-green or blue-yellow. (also red-green is most common, 5% of males)

• Complementary nature of after images

• Retinal ganglion cells code colour in an opponent mater

Ganglion cells code colour

• three cones, opponent process mechanism

• Yellow light stimulates red and green cones etc

Colour and the cortex (Pearlman et al 1979)

• male patient w/ v4 lesion (ventral pathway)

• Poor colour matching. Problems with choosing clothes, ripe fruit, sees life in shades of gray

Oliver Sachs interview

• the case of the colourblind painter

• Tomatoes black, had to close eyes to eat bc all of it looks bac

Perception of colour summary

• mapping of wavelength

• We need both opponent and trichromatic theories to understand colour (stage 1: trichromatic. Stage 2: brain subtracts signals from each other, (if fire for green but stops for blue, separated?)

• Conscious perception of colour in cortex

The puzzle of depth perception

• how construct 3D from 2D retinal perception?

• How do we know true size of any object?

(IMPORTANT FOR MCQ ANSWER THESE)

The principal monocular depth cues

• depth cues: monocular cues, binocular cues

• Monocular: pictorial cues (photos, drawings), motion parallax)

• Pictorial: interposition, size, linear perspective, texture, haze, shading, elevation

• Binocular: convergence, retinal disparity

Occlusion/interposition

• when something is covered, believed to be in the back

Elevation or height

• higher = further back

Reative size

• Bigger object is closer

Linear perspectives

• further away = smaller

• parallel lines converge at a vanishing point

Aerial perspective

• further images travel through atmosphere, more distant less colur. faded like distant mountains

Light and shade

• creates depth through light and shadows

Why pictorial cues effective?

• mimics irl

• we interpret pictorial cues in art in the same way we interpret 2D retinal image

Size constancy

• our perception of size of objects is relatively constant. Estimate of distance

• When perception of stiance is wrong, size constancy breaks down

• Seen in moon illusion and Ames room illusion (IMPORTANT)

Moon illusion

• moon looks larger by horizon than in the sky

• we have a bad understanding of how far the moon is

• objects on the landscape suggest to us that the moon is very far away but for the zenith moon, there are no cues for distance. we assume it is closer this way

• moon subtends the same retinal image in both cases, we erroneously perceive a small (zenith) and a large (horizon) moon

Gibson’s visual Cliff Experiment

• Gisbon and Walk

• Put kids on visual cliffs

• Kids encouraged to climb over cliff, small crawling kids mostly said no

• babies with more crawling experience avoid it more

• suggests human experience plays a role in perception of depth in humans

• 6 month old

(1960)

Smell & taste known as

• chemical senses

• near senses

• the minor senses (okay Kant, 1798)

What are men better at?

mothballs, beer, ivory soap, bananas, brut afershave, bourbon, sherry, black pepper, rasperry syrup, sardines

Ishihara Colour Blindness test

• the numbers and colours thing

The perception of colour & the theories

1. colour and hue are psychological attributes of the wavelength of light

2. our perception of colour (hues we can discriminate) reflect neural coding of both trichromatic & opponent process nature

3. conscious perception of colour is based in cortex