Does Beauty Lie in the Face?

As the saying goes, ‘beauty is only skin-deep’. However, many times we cannot help but fall for an attractive face: the first impressions of a person do create an impact on our minds. What is considered ‘beautiful’? Are there features of faces across cultures that people find more attractive?

Facial Symmetry

According to researchers, a face is perceived as beautiful if it is symmetrical and represents the average traits of the population. Our eyes recognize symmetrical faces with similar proportions on left and right side of the face. The quest to define a golden standard for a facial feature - for example, the size or shape of the eyes or lips - dates back to antiquity. The Ancient Greeks believed that the essence of beauty lied in the golden ratio of 1:1.618. More recently, researchers have discovered that people find a female face attractive when the distance between the eyes is just under half of the width of the face. They also found that the eye-to-mouth distance should be just over one-third of the height of the face. These two ratios have been termed as the ‘golden ratios’, which correspond to that of an average face [1].

Example of faces with different length and width ratios. Boxes mark the optimal length and width ratios that people found attractive [1].

 

What is the reason behind the choice of such features? This can be explained by two existing theories: one is an evolutionary aspect where humans tend to choose healthy mates with physical characteristics resembling the average population. The other is a cognitive aspect where, due to repeated exposures, we tend to prefer prototypical facial features which are easier to process.

Golden ratio: can beauty be quantified? 

So, are facial preferences based on nature or nurture? Do we have a preference for certain faces as babies? The answer seems to be: yes! Babies of 2-3 months tend to look at attractive faces for longer time than unattractive ones [2]. The perception of attractiveness is also affected by familiarity: Hazda people, hunter-gatherers from Tanzania who have not been exposed to European faces, found the average face of a Hazda more attractive than an European face [3]. But spatial aspects of the face are not the only determinants of attractiveness - sexually dimorphic features like full lips and longer eyelashes also influence what people find attractive [1 ].

The Power of a Smile

A smile has more powerful influence on people’s perception than facial features or makeup, according to psychologists. People with genuine smiles were seen as healthier and more attractive by virtue of being optimistic and cheerful than people with blank expressions [4,5]. Thus, the secret to healthy appearance and being attractive? Smile!

For the evolutionary basis of beauty, check out Helge's article on page 5. Given the fact that there is an innate bias inside all of us towards 'beautiful' faces, it is even more important for us to think twice before making judgements on other people based just on their appearances!

How an average American woman will look like in 50 years
(Courtesy: National Geographic)

What will future humans look like?

It has been predicted that globalization, cultural diffusion and interracial marriages will eventually homogenize the human population, averaging out more and more people's traits such as hair, eye color, facial features, and eye shape. Dominant traits will be expressed more than recessive traits (which need not one but two copies of the gene to be expressed). In other words, we are going to become a huge amalgamated race!

by Aarti Swaminathan, PhD Student AG Schmitz

 [1] Pallett P.M, Link S, and Lee K. Vision Res. 2010.
 [2] Hoss R.A. and Langlois J.H. The Development of Face Processing in Infancy and Early Childhood: Current Perspectives. 2003.
 [3] Apicella C.L et al. Perception, 2007.
 [4] Golle et al. Cognition and Emotion, 2013
 [5] Jones A.L et al. Visual Cognition, 2017.

The Evolution of Love

Let me tell you about the birds and the bees. And the flowers and the trees. And a thing called love…
But hey … what is LOVE, except for the most popular topic of song lyrics?

What is Love?
The urban dictionary gives the following definition: “Love is nature’s way of tricking people into reproducing” [1]. Hm… why didn’t we just continue to be self-copying RNA as described in “The Selfish Gene” by Richard Dawkins, or simply procreate by cell division [2]? The clue is that sexual reproduction brings enormous advantages in terms of fitness: Mutations occur naturally in every organism all the time. Some may be harmful, some without impact and others may be highly beneficial. Maybe a mutation in a structural protein could give a protist sturdier ciliaries, allowing it faster movements and a great advantage in escaping predators. However, only the individual carrying the mutation will benefit from it unless it is shared. And basically, sexual reproduction is nothing else but sharing your genome with someone else. This someone will not benefit in person, but his and your offspring will. Thus sharing is caring. But does caring equal love?

Source

I'm Too Sexy...
In general, mating means higher cost for an individual at first, but pays off with increased fitness of its progeny and gene propagation. But of course, not every individual wants to mate with any other. Hence, mating strategies developed to maximize benefit. Mating strategies vary in complexity: a pretty straightforward strategy is to release attractive molecules to acquire a random partner. However, the more costly the reproduction itself, the more prudence in partner choice is advised. The decision about a partner is usually made by the female, thus males of many animal species have developed specific attributes and/or courtship behaviors that may not serve any practical purpose other than attracting a female’s attention and influencing her choice.
Birds give great examples of this: peacocks grow their beautiful and immense tails to impress females. These have no use other than to signal “I am so fit and healthy, I can afford an entirely useless, giant plumage!” (see also 'You Have Beautiful Eyes, Hundreds of Them'). Similarly, bowerbird males construct little lodges from sticks, grass, and leaves, which they even decorate with flowers, shells, and other colorful and shiny things they collect. If the lodge is impressive enough and the female decides to mate, they entirely abandon the lodge to build a nest suitable for breeding elsewhere.
Humans, too, possess attributes that serve reproductive rather than survival purposes. Compared to other primates, humans have features such as “concealed ovulation, extended female sexuality when not fertile, large visible breasts even when not lactating, large spongy boneless visible pensises relative to body size even when not sexually aroused, relative hairlessness that reveals skin quality, full lips that may mimic female genitalia by exposing skin that simulates mucosal membranes”, as discussed in detail by psychologist Lawrence Josephs [3].

You and Me, Forever
But mating alone does not yet guarantee successful procreation. A lot of further effort needs to be invested by parents to actually ensure the survival of offspring, especially in higher mammals. For humans, this can be up to twenty years! For this purpose, nature developed strategies beyond the "hit and run" approach to make mating partners cooperate until their progeny can survive on its own. Bonding mechanisms cause partners to team up and cooperate until descendants can survive independently [3,4]. This may lead to monogamy (or serial monogamy) as a favored type of relationship.
Nowadays, psychologists discuss compassion, a feeling most of us would also associate with love. Compassion also developed to ensure survival chances for vulnerable offspring because it motivates individuals to join forces and cooperate for the sake of their progeny [5]. Even early evolutionists such as Darwin considered what he called “sympathy” to be one of the strongest human instincts. While all of this totally makes sense, it does not really fit our modern-day definition of “love”.

LOVE IS THE ONLY SOCIALLY ACCEPTED FORM OF MADNESS

Maybe, it is more appropriate to talk about the psychological term “romantic love”. Psychologist James Leonard Park provides a sarcastic explanation of romantic love as a hoax or urban legend [6]. Indeed, considering archeological finds from the beginning of mankind, there is evidence for different forms of courtship behavior and for the concept of marriage, i.e. partnership between man and woman in order to maintain monogamy and raise children. Still today across the globe, people get married for practical reasons only, without any romantic consideration. Where does romance come into play then? Apparently, it is the relatively modern invention of medieval troubadours and minstrels in France [7]. Since then, European culture has spread all over the world, the newly invented concept of romantic love has entered folk psychology and is ubiquitous in songs, novels, television, and movies. Cultural imprinting, one could say.


You Drive Me Crazy
Nonetheless, most of us have experienced romantic love, and it is commonly perceived as an altered state of consciousness or “the only socially accepted form of madness” [8]. Not only because of these definitions, involving consciousness and insanity, psychologists and neurobiologists began to explore what underlies romantic feelings in the brain. Even though research has so far correlated brain regions and autonomous nervous system activity with feelings of love and identified some brain chemistry that elicits affection, science is far from answering the question: What is love?
It's good to know that instead, there are plenty of songs still to come that can tell us the answer.

[1] http://bit.ly/1fTAtUl
[2] Dawkins, "The Selfish Gene", Oxford University Press, New York, 1976
[3] Josephs, Am Acad Psychoanal Dyn Psychiatry, 2010
[4] De Boer, Neuroscience, 2012
[5] Goetz, Keltner and Simon-Thomas, Psychol Bull, 2010
[6] http://bit.ly/1mHJD9x
[7] http://bit.ly/1g2veC6
[8]http://bit.ly/1nnGFXd

by Bettina Schmerl, PhD Student AG Shoichet
This article originally appeared 2014 in CNS Volume 7, Issue 2, Neuroscience of Love

From Molecules to Mouthwatering - An Overview of Taste Physiology

By now the stores are overloaded with easter-candies and it gets harder and harder to steer clear of the tempting sweets. Ever wondered why so many people have a sweet tooth? Or how we can taste the wide range of flavors that span all the different types of global cuisine? 

Our sense of taste is important for both of the above. Taste is a chemical sensation critical for survival because it allows us to detect nutrients and toxins in the foods we eat. Although it works in conjunction with the olfactory system [1], it can be considered the final step in consumption at which we accept or reject food. Chemoreceptors on the tongue detect five different fundamental tastes: salty, sweet, sour, bitter, and umami (glutamate) [1]. 

WE HAVE 1000 ODOR RECEPTORS AND 50 TASTE RECEPTORS

Taste buds consist of 50-100 taste receptor cells with a central taste pore, and are located all over the surface of the tongue and soft palate. The taste buds line small projections on the surface of the tongue called papillae and project to dendrites from the cranial nerves 7, 9, and 10, which are responsible for conveying taste information from various regions of the tongue and palate. At the ganglion level, most neurons receive input from exactly one taste modality, but there are also neurons that respond to combinations of taste-receptors such as bitter-sour, sweet-umami or sweet-salty [2].

Taste vs. Smell
The senses of taste and olfaction work closely together to create our perception of flavor. There are as many as 1000 odor receptors in the olfactory bulb, but only 50 different taste receptors – the less precise taste receptor system recognizes fewer different chemical cues, and multiple ligands can bind to the same taste receptor. In fact, some very distinctive flavors cannot be detected without the aid of olfaction, such as coffee or chocolate [1].

An Evolutionary Function
Let's think about each of the five fundamental tastes in terms of its survival-relevant function for the organism. A family of specialized taste receptor proteins (TR) detect the different tastes. The T1R family of receptors detects sugars and amino acids. These receptors have a relatively low affinity, which allows them to detect only the foods that are rich in these tastes (i.e. that have a lot of sugars or amino acids). Bitter taste is mediated by the T2Rs, which have a relatively higher sensitivity. This is helpful because bitter tastes are often associated with compounds that are poisonous. Salty taste is mediated by the detection of sodium chloride and is mediated by ENaC’s – epithelial sodium channels [1]. Sour taste, however, is a mechanism for the detection of low pH, or acidic substances, found in spoiled or unripe foods [3]. 

Species and Individual Differences 
The sequence of these receptors is very important for determining the specific chemical signals that are recognized by a given receptor. For example, humans are able to detect the chemical aspartame as sweet, while rodents cannot detect it at all. In fact, if transgenic rodents express the human sequence of T1R receptor, they gain the ability to taste aspartame. Cats, on the other hand, lack the functional T1R receptor for sweetness and therefore cannot detect sweet tastes.

CATS CAN'T TASTE SWEETS

The same precise structure-function relationship exists for amino acids as well. For example, the human TR for amino acids can recognize glutamate with a 10-fold higher affinity than other amino acids while the same receptor for rodents is a general amino acid receptor, which recognizes all amino acids relatively equally [1].
Going one step further: The sequence of the genes for the taste receptors gives rise to threshold differences and the ability to detect different tastes between individuals. For example, about 75% of people detect the compound phenylthiocarbamide (PTC) as sharply bitter, while 25% cannot taste it. The ability to (or not to) taste PTC depends on two major variations in the sequence for the bitter taste receptor gene. There is one primary allele that allows for tasting and one that does not. Individuals who have inherited two non-tasting alleles cannot detect the compound, those who have inherited only one “tasting” allele can detect it, and those who have two of the “tasting” alleles are super-tasters, detecting PTC at even lower concentrations [1].

Taste Map Debunked
While the sequence of a person’s individual taste receptors is very important for their ability to perceive tastes, the location of the taste on their tongue is not. In spite of the commonly taught “taste map” in which different tastes are said to be detected on different regions of the tongue, recent work suggests that the taste buds in all regions of the tongue contain a variety of different types of receptors. Although the distribution is not necessarily uniform, the differences in the relative sensitivities of tongue regions are likely to contribute only subtly to the distinct perceptions of taste [1]. 

[1] Squire, Fundamental Neuroscience, 2008
[2] Barretto et al, Nature, 2015
[3] Huang et al, Nature, 2006

by Lauren Mamer, PhD Student AG Rosenmund
This article originally appeared September 2015 in CNS Volume 8, Issue 3, Food for Thought.