Guest Post: The Scent of a Handshake

Today's guest blogger is Idan Frumin, a student in the group of FruminProf. Noam Sobel in the Neurobiology Department.  Their research on the transmission of odor compounds while shaking hands appears today in eLife.

It all started one day after lunch, sometime back in 2011. We sat in the lab’s living room (Yeah, we have a living room. And a bedroom. And a blind pet cat. But that’s a different story), when Noam asked – ever wonder why people shake hands?

– To show you don’t have a saber up your sleeve – I immediately retorted.
– But that seems odd, doesn’t it? After all, we’re not in the Middle Ages anymore, he responded.

Noam had just gotten back from an international conference, one of many, and did there what all better scientists do in their leisure time: observed.

– and what if I tell you people sniff their own hands right after they shake someone’s hand?
–You’re kidding right? what are we, rodents?!
–Well, you should know by now we’re not that far from that...

So we devised a simple paradigm to test this. Do people really sniff their hands following a handshake? And is it directly related to the handshake? And more importantly – is it related to our sense of smell?.. Which is our lab's frame of reference for, well, almost anything.

We already had most of what it takes – we have rooms where we can put human subjects and sit them relatively comfortably on a dentist-style chair (talk about comfortable…), we have CCTV cameras that only need to be set up, and plenty of subjects that come and go for the various experiments taking place in the lab. So off we went. We knew we needed a big sample of subjects to be able to say something meaningful, so we started with 60. The paradigm was pretty simple – A person was seated alone in the room, unaware at that point that they are being filmed. After three minutes of idle seating, one of my lab mates (or myself at times) would enter and either shake or not shake the subject’s hand, saying the same “greet” sentence. The subject thought they’re waiting for the “real” experiment to ensue, so we told them we are getting everything ready, and that the experiment will start momentarily. After an additional three-minute period, the experiment was essentially over.

Analysis of substances on the rubber glove after a handshake revealed that chemicals from human secretions were transmitted through handshake alone Analysis of substances on the rubber glove after a handshake revealed that chemicals from human secretions were transmitted through handshake alone

Then the fun part started. Watching this quantity of videos could be "a bit" tedious, but it has its perks embedded - people do the most hilarious things when they are alone... the most interesting for us - they constantly touch their faces. Much as Noam and that late-90's song both foresaw - "you and me baby ain't nothing but mammals," and may we add - indeed not very far from rodents so it seems. We constantly "groom."

One of the more perplexing results was the "self-sampling" behavior after encountering another individual -- as if to assess or validate one’s own place within some sort of hierarchy.

But the jackpot was the statistics of before and after handshake - there was a significant and substantial increase if a handshake was involved!

After a handshake (left), a volunteer sniffs her “shaking” hand more (right) (photo illustration) After a handshake (left), a volunteer sniffs her “shaking” hand more (right) (photo illustration)

Though we got nice results with 60 subjects, and presented those in two international conferences, we wanted something more comprehensive to tell. Is this effect happening only between males and females? Is it gender specific at all? So up went the count - to 160 subjects, 20 in each possible combination of subject, experimenter and shake/no shake. And this number continued to swell as we added more conditions and more controls. You can check the article to see what we did there. Calvin Klein was unwittingly involved as well...

Along the way the paper got some pretty and colorful additions. One day Ofer came and asked - did you check and see WHERE people touch their faces? I replied "Well it's a very interesting question which I am not going to address, but feel free to check that". So he did just that, and the answer became figure 2C - which I must say is one of my favorite pieces of art since. Another day Yaara wondered what actual chemicals are transferred when we shake hands, and that’s Figure 1.

Sobel-Frumin 2 Heat map: The likelihood of people touching their faces close to the nose was highest (red, yellow) after a handshake (left)

When people ask why study such stuff, and what scientific field or discipline do such studies fall under anyway - we have several answers. First - because it's there - and it's interesting. Everyone shakes hands and if the common explanation as to why is partial - we need to amend it. We do basic science - and the notion of applicability is important but not the main thing. Second, this really serves a broader argument - in which our stand is quite obvious - there is no advantage for man over beast, and we're a part of the greater evolutionary tree.

So here you have it - a story that started off as a casual conversation in the living room of a lab, and 280 subjects / cups of coffee / new grey hair later became the paper you ought to read, if you haven’t done so already!

 

 

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Im and throwed. I was studying in the library recently, and the guy who sat next to me had a friend come over and JUST shake his hand. He proceeded with his 'studying', but occasionally scratched his nose (which I noticed because moment generating functions were not generating ... 'moments'). I understand why now.

By Mmabyala Malete (not verified) on 05 Mar 2015 #permalink

I personally think that people smell their hands because it way of know what the person you shake hands with have been touching or doing.

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By Siphokazi Gqirana (not verified) on 15 Mar 2015 #permalink

this is interesting,so i can basically get a person to sniff any substance i want by just applying it on my hand and then shake their hand...cool
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By Tumiso Monaiwa (not verified) on 16 Mar 2015 #permalink

when I read the topic, I was expecting something to do with bacteria and what-so-not, interestingly enough I found something more interesting. I am so going to take note of this from now on. My question is now, does it come naturally or people do it deliberately or maybe it is the matter of the mind?

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Definitely mind, and subconscious. If you tell people they have been sniffing their hands, they won't believe you.

I find it fascinating that most people actually smell their hands after a handshake. It could be because the subject was exposed to either familiar or unfamiliar smells that concern the subject from the person shaking hands with the subject. Then again it could also be a seasonal issue as in Winter people are more likely to touch their noses due to the common cold.

I do not think that people smell their hands after a handshake because I have never noticed it and I have never done that myself. I believe there is confusion between just touching your face and smelling your hands after a handshake.

By Anthony Micklesfield (not verified) on 29 Mar 2015 #permalink

Indeed, the scientists thought of that: They checked to see if the subjects inhaled more -- sniffing, on other words -- after the handshake.

I do not think that people smell their hands after a handshake because I have never noticed it and I have never done that myself. I believe there is confusion between just touching your face and smelling your hands after a handshake. 15120521

By Anthony Micklesfield (not verified) on 29 Mar 2015 #permalink

I once read that people subconsciously choose partners according to their scent. This, apparently due to the fact that everybody's scent is unique to their genetics. People would then choose someone that smell completely different than they do. This it is a natural process to ensure stronger offspring due to genetic diversity. Maybe people identify possible partners by subconsciously smelling their hands after greeting someone? I do believe that many people may deny this because the cannot recall smelling their own hand after greeting someone by hand, but I also believe this is subconscious and not at all intentional.

By Cherise Swanepoel (not verified) on 30 Mar 2015 #permalink

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By Cherise Swanepoel (not verified) on 30 Mar 2015 #permalink

Interesting, considering the fact that I may have also unconsciously touched my face after a handshake. Is there a mental shift in the way the individuals view the other person after they have sniffed their hands or is just simply an unconscious act?
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By Michaela Govender (not verified) on 31 Mar 2015 #permalink

This is very interesting and I'm not finding it hard to believe because I might have smelled my hand after a handshake more than once. It could have been subconsciously or it could have been out of curiosity. But I also think that people don't necessarily smell their hand but they do touch their nose with the hand they used to shake with. It is also interesting to find out what your hand smells like after a handshake and you identify that person by that particular smell.

By Liza van Rooyen (not verified) on 31 Mar 2015 #permalink

This is very interesting and I’m not finding it hard to believe because I might have smelled my hand after a handshake more than once. It could have been subconsciously or it could have been out of curiosity. But I also think that people don’t necessarily smell their hand but they do touch their nose with the hand they used to shake with. It is also interesting to find out what your hand smells like after a handshake and you identify that person by that particular smell.
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By Liza van Rooyen (not verified) on 31 Mar 2015 #permalink

i think higher classes are the ones who do this to lower classes. what i have noticed is that rich people are the ones that tend to do this , since they think they are more clean that people at lower level and i think they do this knowingly and if you tell them after they just pretend they did not know to hide there snobbish behaviours
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By sendra kawa (not verified) on 31 Mar 2015 #permalink

Do you think we subconsciously form our first impressions of people based on the scent of a handshake? If so, would it not make sense that people with a heightened sense of smell have difficulty changing their first impressions of people? 15037780

By Olga Neveling (not verified) on 31 Mar 2015 #permalink

What an interesting research task! This is definitely not something i would ever have noticed or looked into in the past, but now that it has drawn my attention ill be keeping an eye out as this may be very intriguing to witness. One has to consider that there could however be a clash between natural instinct for us humans to touch our faces regularly and the intention to smell our hands after a handshake. This could lead to a mistaken conclusion. This is still, undoubtedly a topic which grabbed my attention.
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By Kaycee Skinner (not verified) on 31 Mar 2015 #permalink

I have never really noticed this happen ever and maybe i should try and observe people's actions more but I don't necessarily think that people smell their hands each and every time they shake somebody's hand, they could have had an itch or something. In the blog it was not mentioned how successful the experiment was, did every single person experimented on smell their hands or just half? Please may you clarify on this

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By Thembekile Mkh… (not verified) on 31 Mar 2015 #permalink

I live in a rural area and it is more common to greet people by a kiss than with a handshake, unless men greet each other or if you are German. I prefer to be greeted with a kiss as people's lips do not touch public toilet seat lids or shake other people's hands that did not wash their hands after they have been to the restrooms. Interesting enough, people that greet with a kiss also touch their faces, before and after the kiss.

By Lize Claassen … (not verified) on 01 Apr 2015 #permalink

If I meet a person for the first time I often touch my face because I feel nervous and uncomfortable. I researched this and found that people often touch their faces if they feel discomfort. This may be the reason people touch their faces after handshakes as they are meeting people for the first time.
To further this study it could be tested with people who already know each other.

It is interesting to see the natural animalistic behaviors that humans often exhibit. I am studying genetics and so topics on evolution fascinate me.

By Joanne Dilnot … (not verified) on 01 Apr 2015 #permalink

This is a very interesting study as most people can identify other individuals purely by smell. I have experienced this when walking into a strangers home. The smell of certain places can be remembered and associated with specific things, as with the unique smell of "home". I think the same science applies to the handshake experiment. Our instinct is to remember the smell and store it in our memory or to associate it with particular things.

By Alri Richter (not verified) on 01 Apr 2015 #permalink

I have noticed myself smelling my hand after a handshake...and thereafter quickly proceeding to the nearest tap. This was at an age of about 13 but as I became older I found myself becoming more and more against touching my face in public especially after being in contact with other people. How would this instinctive smelling of the hands explain that or am I just the excepting to the rule?

By Charldon Viljo… (not verified) on 02 Apr 2015 #permalink

This is very interesting. I have always thought that most people avoid the handshake because of public health issues. Now i learn about smells and all. Its pretty simple to understand why most people avoid handshakes including myself after reading this. Too much goes on with hands!

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This is a very fascinating study. Every person has a distinct scent and by subconscioulsy smelling one's hand after shaking another person's hand allows us to remember the other person's scent. i believe that once the body has recognised another person's scent, they can pick it up from far the next time they meet, however subconsciously. Does the scent recognised by the body resemble a specific personality trait and does it contain specific elements which allows the person to be attracted to another? u15007473

I agree as the specific smell can be associated with a specific person or even a group of individuals without you even seeing that person or that group. When your smell receptors pick up that specific smell it automatically associates it with the person or group of individual without you actually being able to see them.

By Tholi (15177735) (not verified) on 03 Apr 2015 #permalink

I strongly agree with your statment. Alri because I too can identify my cousin and her family with just the scent they are giving off when ever they I near. I don't have to literally have to see them to know that they are here.

By Tholi (15177735) (not verified) on 04 Apr 2015 #permalink

It's fascinating to observe the unconscious mind! Studies shown that people tend to touch their face even more often if they shaken their hands with someone with the same gender! It would be interesting to study the reason why we subconsciously do this?

By Anike Lucas- 1… (not verified) on 06 Apr 2015 #permalink

This is something that I have never even noticed. So of course I just had to see it for myself. I was astonished by how many people sniff their hands after a handshake. I then started to wonder if I also have this strange habit and if I do, how have I never noticed it before?

By Tane (15001874) (not verified) on 06 Apr 2015 #permalink

Wow! And we thought we left the caveman behind. A very interesting study. I am not completely sure about the scientific significance of the information but will surely be watching closing the next time I greet anyone with a handshake. It would be interesting to find out if the different places touched on the face, could be linked to more than smell; like for instance an attraction or dislike towards a person depending on the place the person would touch their face and whether there would be a difference in the response between opposite genders. This could really give you an advantage in the dating game.

By u15027725 (not verified) on 06 Apr 2015 #permalink

What amazes me about this article is that humans and animals, even rodents, subconsciously act the same in similar situations. The fact that most people would deny their actions, shows that it's not controlled and that it is done unwillingly. These types of researches intrigue me, as it seems simple and is unusual, but the results prove to be very useful and sheds light on other topics.

By Van der Walt, M (not verified) on 06 Apr 2015 #permalink

I agree with Alri Richter. The thought of entering a strange home and always noticing the smell also occurred to me when reading this article. It is interesting how big the role of smell is in our senses even though we do not always realize this. 15038336

By Maryke du Plessis (not verified) on 06 Apr 2015 #permalink

I personally think the environment and situation in which people greet each other will have an influence on whether the person smells their hand after greeting another person. For example when you are at a fancy business dinner party you would act more professionally and therefor not smell your hands after greeting someone as it can easily come across as rude.
It would be interesting to further this study with testing the influence of the environment in which people greet each other as well as testing the influence it has when the people already know each other as Joanne Dilnot suggested.
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By A Potgieter 15004512 (not verified) on 06 Apr 2015 #permalink

This is very interesting. I have always thought people touch their faces after a handshake maybe as a reflex action, more like it just happens without really associating this behaviour with any thing peculiar. Could this also be due to man's curiosity or maybe people just trying to associate certain smells with something?

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The concept of smelling my hands after a handshake is quite strange. Although not completely aware of what i do after a handshake i can not recall ever smelling my hands. For this experiment, i was wondering if you had considered that the subjects might have been touching their faces as either a nervous reaction for waiting alone or just some unconscious action that they might do?
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By Davison, K (not verified) on 07 Apr 2015 #permalink

It’s fascinating to observe the unconscious mind! Studies shown that people tend to touch their face even more often if they shaken their hands with someone with the same gender! It would be interesting to study the reason why we subconsciously do this?

By Anike Lucas- 1… (not verified) on 07 Apr 2015 #permalink

It is very interesting to see remnants of our evolutionary ancestors in modern humans. Of course they actually made practical use of this 'smelling' another person. What I want to know is whether our subconscious influences our opinion of a person based on his or her smell.
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By Bertus van Heerden (not verified) on 08 Apr 2015 #permalink

Well it is a very intriguing 'fact" if i may, I myself have never noticed this behaviour, but witnessing this would be very interesting.
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Personally I think the environment and situation in which people shake hands and greet each other also has an effect on their behavior and the way they react after they shook hands, for example when a person is at a fancy business dinner party the chance of them smelling their hands would be less, because it can easily come across as unprofessional. But in a park while walking your dog it would not even be noticed if a person smells their hands or touches their face after greeting someone. Therefore I think to further the study they could place people in different situations to determine if the environment has an effect.
I also agree with Joanne Dilnot that it would be interesting to see whether people smell their hands after greeting someone they already know.
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By A Potgieter 15004512 (not verified) on 09 Apr 2015 #permalink

I've never noticed this before! Such an interesting experiment. I tried it with my aunt and uncle when they came to visit, shaking my uncle's hand and giving my aunt a hug. I watched their actions closely afterwards. My aunt fixed her clothes but never touched her face whereas my uncle rubbed his nose almost immediately after sitting down. Maybe just a coincidence but I'm definitely going to watch people more closely from now on after I've had interactions with them.

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By Z Verster (not verified) on 09 Apr 2015 #permalink

Handshake greetings dated many years shows a symbol of solidarity and appreciation among people. That is why in most of the business meetings whereby a good conclusion is reached it must be ended with handshakes from both parties, but in case of disagreement handshakes are not applicable. Also it is not entirely true that people sniff their hands after a handshake in most of the cases. I

By Michael George… (not verified) on 09 Apr 2015 #permalink

iIt’s fascinating to observe the unconscious mind! Studies shown that people tend to touch their face even more often if they shaken their hands with someone with the same gender! It would be interesting to study the reason why we subconsciously do this?

By 150 32 907 (not verified) on 10 Apr 2015 #permalink

Wow! And we thought we left the caveman behind. A very interesting study. I am not completely sure about the scientific significance of this information, but I will surely be watching people very closely next time I greet them with a handshake. It would be interesting to find out if the different places touched on the face could be linked to more than a smell. For instance an attraction or a dislike towards a person depending on the place the person would touch their face; and if there would be a difference in the response between opposite genders. This could really give you a big advantage in the dating game.

By u15027725 (not verified) on 11 Apr 2015 #permalink

I find this behaviour very interesting and something that I have never noticed myself, although I don't greet people with handshakes very often. This behaviour would be very interesting to test and observe in an uncontrolled environment. However, if I were to test it on myself the results would be unreliable because I am now aware of the behaviour of touching of one's face after shaking hands and would most likely make a conscious effort to avoid said behaviour. Therefore, I would only be able to observe other's reactions following shaking hands.
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By Aimee Serafini (not verified) on 12 Apr 2015 #permalink

This is extremely interesting. I have never noticed it before but that shows how inattentive we are and how much we can improve on our observing skills. I think it is a an excellent way to remind us that we are only animals with basic instincts and we are subconsciously dependent on our senses. I have read an article that explains the connection between the smell of a person and his/her attraction. I would love to see results on male vs. female. Maybe we can change to 'love at first scent'.

By Danielle van Wyk (not verified) on 13 Apr 2015 #permalink

The question I have now is whether a person's smell subconsciously influences our opinion of him or her?

By Bertus van Heerden (not verified) on 13 Apr 2015 #permalink

I think that the research is very interesting but the results rather presumptuous. The fact that the experiment is based on a population of such magnitude or size and the fact that the very same experiment is conducted in a lab portray the idea of the substances used in a lab which everybody knows it is the practical nature of such an environment, and thus many individuals would naturally be eager to sniff anything they make contact with.(15142672)

By Thabang Matsei (not verified) on 13 Apr 2015 #permalink

I find this study very interesting. Growing up, I have developed three main ways of greeting people. When greeting friends, I generally hug them. For family it's usually a hug and a kiss on the cheek. Strangers I tend to greet with a handshake. The way a person shakes your hand gives you an immediate impression of them. It's interesting to learn that the smell and chemical transfer that occurs during the hand shake forms a subconscious part of that impression as well. It's also intriguing to learn that we have certain "habits" associated with the hand shake form of greeting. I wonder if that's the same with the other forms of greetings we have developed?

By Anita van Deve… (not verified) on 13 Apr 2015 #permalink

I find this extremely interesting. I have never noticed it before but it shows how inattentive we are and how much we can improve our observation skills. I read an article about the link between smell and attraction of a person. I would love to see the results of male vs. female. Maybe we can change to "love at first scent".
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By Danielle van Wyk (not verified) on 13 Apr 2015 #permalink

I is a very interesting fact that I have never known before. I would definitely pay more attention to notice it.

By Carike Karsten (not verified) on 13 Apr 2015 #permalink

I think it is strange, but it is human nature.

By Petroné Fechter (not verified) on 13 Apr 2015 #permalink

Very interesting,I just released now that I do the same thing. To be honest, I don't think about it at all, it just happens. Which makes me wonder, did the research reveal whether it is voluntary or involuntary ?
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By Sense Itumelen… (not verified) on 13 Apr 2015 #permalink

I also the very same thing (touch my face a lot when alone), this is very interesting. This post is very scientific though people may think that it is not. It talks about our everyday lives and of what happens daily. According to me and to what I have seen shaking hands shows respect, and it is a way of welcoming the person greeting you.

By Marcos JI (15056024) (not verified) on 15 Apr 2015 #permalink

Very remarkable observation made. It is astonishing what humans do involuntarily and have in common with each other and with other mammals such as rodents. Reading this however makes me ponder upon the fact that do humans do the same when greeting in other ways such as giving a peck on the cheek, or a hug greeting or by simply waving ?

By Sughra Hakim, … (not verified) on 15 Apr 2015 #permalink

One cannot help but wonder how many times they have observed the rather common tradition of shaking hands but never thought that due to several biological changes that are a result of chemicals being transferred during shaking hands would lead to the individuals sniffing their hands. this is quite intriguing that a simple hand gesture could be further explored and explained in such a scientific way rather than a social way.
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By Katlego Ntshudisane (not verified) on 16 Apr 2015 #permalink

This information is very interesting...This makes me think who was the first human being who invented this revolution of this gesture

By Nomaswazi (not verified) on 17 Apr 2015 #permalink

This information is very interesting…This makes me think who was the first human being who invented this revolution of this gesture??
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By Nomaswazi (not verified) on 17 Apr 2015 #permalink

This is a really interesting observation! I always had a different approach on what a handshake told you about a person for example if someone had a firm handshake they would be more hard working and trustworthy.Since I've read this article I think I will be a lot more observant. The only problem I have with the experiment is that all the subjects were waiting, when you are not busy you have a habit of touching your face. Will they find the same results with subjects that shake hands before starting business?
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By Katherine Mcfarlane (not verified) on 17 Apr 2015 #permalink

What an interesting read! I was compelled to observe the people in my surroundings and this has proven to be true most of the time. What's more is that I even caught myself out at some stage, that left me dumbfounded. Human are interesting beings, however it is the things we do when we are not even aware that make us fascinating to observe. What other unusual things have been dicovered about the human race?

By Mashudu u15387349 (not verified) on 17 Apr 2015 #permalink

what an interesting read! I was compelled to stop what i was busy with and observe the individuals in my surroundings and this theory has proven to be true majority of the time. I even caught myself out at some stage, what an eye-opener! Human beings are indeed an interesting race, but what makes us more fascinating is the things that we do unaware. Are there any more unusual things that humans have been said to do?

By Mashudu Phathe… (not verified) on 18 Apr 2015 #permalink

I would like to start off by saying that my comment is part of a research assignment that I have to complete for the University of Pretoria. I found this topic rather bizarre as I have never noticed that people smell their hands after a handshake. From personal experience I find I always touch my face when I'm feeling uncomfortable or shy, which brings me to the question of whether the smelling of the hand is based on behavioural and emotional feelings towards first introductions, rather than the remembrance and observation of someone.
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By B.S Kramer (not verified) on 18 Apr 2015 #permalink

One cannot help but to think about the number of times they have observed the tradition of shaking hands and never attributed the sniffing of ones hand afterwards to biological changes due to a chemical change with the complex human body. It is quite intriguing that a simple hand gesture can be explored and defined to such scientific lengths.Guess there is never a dull moment when it comes to science.(u14018676)

By Katlego Ntshudisane (not verified) on 18 Apr 2015 #permalink

This something I have also never really taken notice of. People have different ways of choosing who they associate themselves with. For example personality and similar interests. Maybe this is also another way of helping one decide whether they would consider being friends with someone or not. I think people tend to gravitate towards people with good body odour as opposed to people with bad body odour. How someone smells also forms part of the first Impression you have of them

By u15084656 (not verified) on 18 Apr 2015 #permalink

I found this study very curious and fascinating, and so is the personalities and mindsets of scientists. Scientists always want to discover new and interesting facts, but also facts that refers to our daily lives. Handshake is so commonly seen in South Africa as a way of greeting that the study is so effective and let people rethink their reactions on certain actions. Danielle van Wyk I love your saying "love at first scent".

By Marissa Boshof… (not verified) on 18 Apr 2015 #permalink

I do not readily agree with your theory A Potgieter. I feel as this is an act that people are not even aware that they are doing environment wouldn't be that great a factor.

By Mashudu Phathe… (not verified) on 18 Apr 2015 #permalink

One cannot help but wonder how many times they have observed the rather common tradition of shaking hands but never thought that due to several biological changes that are a result of chemicals being transferred during shaking hands would lead to individuals sniffing their hands. This is quite intriguing that a simple hand gesture could be further explored and explained in such a scientific.(u14018676)

By Katlego Ntshudisane (not verified) on 18 Apr 2015 #permalink

One cannot help but wonder how many times they have observed the rather common tradition of shaking hands but never thought that due to several biological changes as a result of chemical being transferred from one individual to another this will lead the other individual to sniffing their hand. This is quite intriguing that a simple hand gesture could be further explored and explained in such a scientific way.(u14018676)

By Katlego Ntshudisane (not verified) on 18 Apr 2015 #permalink

Sense Itmeleng Rapetsoa, I believe this is totally voluntary - I myself prefer to avoid smelling my hands (especially after a handshake). I do - though - find face touching the most contagious habit. I have also witnessed this plenty of times. We someone your are talking to touches their face, you immediately feel the need to do so too. Perhaps smelling your hand after a handshake is an individual's way of linking another individual to a specific scent, but then again - how much of their scent can your hand have?

By Jadene Jacobs … (not verified) on 18 Apr 2015 #permalink

I wonder if it could be related to a natural defence mechanism maybe? where your body is subconsciously checking if you have received any harmful chemicals or dangerous substances

By Johann Smith (not verified) on 20 Apr 2015 #permalink

it would be interesting to come across such behavior now that i have read this article.
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