Reading 2 - 'the scent of you'

Question 1

According to the article, what is one evolutionary function of having newborn babies ‘smell good’?

Answer 1

The smell of a newborn baby’s head up until 6 weeks old activates the reward circuitry in the adult brain - similar to that of receiving a treat or drug. Evolutionarily this rewarding nature of a baby’s smell may help drive the want to care for baby’s and their survival

Question 2

Why do armpits smell? List the major components needed to generate body odour, and note any sex/ethnic difference mentioned in the article

Answer 2

Despite being unpleasant, armpit smells aren’t attributed to the presence of small volatile chemicals (like those associated with bad smells of say off milk etc).
BO is instead attributed to the secretion of;
1. Thiols
2. Steroids
3. A diverse set of acids
- these are secreted as odourless precursors that become smelly as a result of the microbes on our body.
- Men secrete more precursors making them more smelly

Men tend to have lots of Corynebacterium which smells pungent. Whereas, staphylococcus is less smelly

Question 3

Do we sniff people when we first meet them? See if you can argue in both directions, using specific information from the article.

Answer 3

Whilst humans don’t overtly sniff other people (generally speaking), we do still use subtle methods of smelling others. Eg. sniffing our hands after shaking someone else’s hand.
There is evidence against pheromones as a means of communication between people, and our use of smell against other people tends to be less common in modern times due to the pressure to reduce body odour. There is still benefit in smelling people, potentially serving a role in kin recognition, disease status identification, emotion conveyence, mate selection etc

Question 4

Volatile chemicals emanating from our body appear capable of changing the emotional state of people nearby. Give one specific example from the article of chemically-mediated emotional reactivity (i.e., I consciously/subconsciously detect emotion X so I consciously/subconsciously react by doing Y).

Answer 4

1. Mate selection
   Body odour of people carrying HLA (human leukocyte antigen) that is dissimilar to our own will be more attractive (may be evolutionary strength to produce children with stronger immune systems) - a meta analysis suggests the HLA theory is only a small component in mate selection
2. Recognising Dominance - can identify winners and losers of a cage fight based off of their smell
3. Sniffing tears from negative emotions (that contains hexadecanal) can lower testosterone in men
4. Smelling someone’s anxiety can produce empathy in the smeller
5. Smelling a loved one can reduce stress
6. Smelling positive emotions can induce happiness in the smeller

Question 5

Give one specific example from the article of chemically-mediated emotional contagion (i.e., I consciously/subconsciously detect emotion X so I consciously/subconsciously also feel X).

Answer 5

Happiness
Smelling positive emotions can induce happiness in the smeller
This happiness can be measured by physiological changes - promoting the idea happiness is contagious

Question 6

Volatile chemicals emanating from our body appear capable of communicating info about our immune system. Discuss two specific examples from the article.

Answer 6

1. HLA - Human Leukocyte antigen variation can attribute for a variation in a person’s smell and is believed to attract others with a different HLA variation. This way, offspring can be more genetically diverse in their HLA to strengthen their immune system. A 2017 meta-analysis suggests HLA variation doesn’t drive sexual attraction, however, we do tend to prefer people with high HLA diversity
2. Individuals sweat more intensely and with a more unpleasant odour when they’re unwell

Question 7

We can often identify genetically related family members by smell. Briefly discuss how this can beneficially drive approach behaviour, and also beneficially drive avoidance behaviour.

Answer 7

Approach Behaviours
Familial bonding is facilitated by smell
- eg. Babies bond to their mothers likely because they smelt their mothers food when in utero, and ex-utero they smell their mothers food in their breastmilk
- eg. mothers can sometimes recognise the smell of their children and if they do, they prefer it to the smell of other kids
- eg. the HLA genetic component of kin recognition

Avoidance Behaviours
Incest avoidance
- eg. parents dislike the smell of their opposite sex children once they reach puberty
- eg. the scent of aggression can be detected particularly by women presumably to help them avoid aggressive men
- eg. Smelling people who are ill - helps us stay away from them
- eg.

Question 8

Many languages “lack a decent lexicon for smell.” Explain what this means, and how it may influence our perception of smell

Answer 8

It’s hard to distinguish or disambiguate odours when there is not a name for that given scent or odour
It is hard to have a conscious awareness of a smell without a suitable name for that smell

Question 9

What language has a large lexicon for smell

Answer 9

Maniq and Umpila, a language spoken by a small population of nomadic hunter–gatherers in southern Thailand and Australia respectively, are such languages. Maniq has a lexicon of over a dozen terms dedicated to smell.

Question 10

Smell in Utero

Answer 10

Smell begins in utero as the chemicals from our mother’s food can cross the placenta, allowing babies to smell their mum’s food.
This may help with babies identifying their mothers milk after they’re born
Could also be a driver for baby/mother bonding

Question 11

Sense of Smell and Disease

Answer 11

Some people like Joy Milne are super sniffers who can smell diseases like Parkinsons.
Anyone however, can learn to detect pneumonia, diabetes, cholera and certain cancers from odours given off in sweat, breath, urine and faeces

Question 12

Does Everyone Produce BO?

Answer 12

No..
Asian people tend to be naturally odourless
This is due to a one-off mutation in the ABCC11 gene
95% of chinese people have this mutation and 70% of east asians
Results in individuals not producing odour precursors

Question 13

Options to mitigate expert bias and whether these work

Answer 13

• Awareness; doesn’t work - for example in visual illusions, we can be aware of the illusion but still don’t see the correct thing
• Formal bias appraisals for forensic scientists - test to see if they’re biased. This is also a weak measure as we often do things differently in a test than in real life so it may not accurately reflect things
• Sneaky bias appraisals for forensic scientists - doing a test where the expert doesn’t know they’re being tested. ie. airport security - but this isn’t always possible
• Peer review - cross-check results with others. ie. having multiple examiners check a fingerprint. however, presently cross-checking tends to only occur when the first expert finds a match and the first examiner gets to pick the second examiner (source of bias). Evidence suggests that with the present selection method only 1% of examiner 2’s disagreed with examiner 1. Then, 15 - 20% of the 2nd examiner disagreed with the first examiner when a fairer method is used