What’s in a blink?

Some of the best “gems” we get from our children are those moments before they go to sleep.  Our children are still young enough to want five minutes with Mum or Dad at bed time.  As frustrating and distracting as I sometimes find the task, once I lie down in the bed next to them and tune into their thoughts and ramblings, I am always grateful that I took the time.

In fact, these precious moments have been the inspiration for many of my blog posts here.  This one is no exception… I lay down with my nine year old daughter last night at bedtime and the first thing out of her mouth was…

…”Mom, how many times do we blink in a day?”
Humans usually blink about 10 to 20 times a minute.  A blink flushes the eye with fresh tears, supplying essential nourishment to maintain a healthy eye surface.  This can refresh the eyes, clear away any dust and debris and prevent infection.  Blinking can also brighten and refresh images received by the retina.

How long does a blink last?

A blink typically lasts about half a second.  If you add all this up we actually have our eyes closed for at least 120 minutes a day.  Blinking does serve the necessary purpose of moisturising the ocular surface but apparently the rate at which we blink exceeds the requirement for clearing the eye.  So are there other reasons for this process?
Yes! Recent studies  have shown that blinking also gives our brain a little “nap”, switching from cognitive to non-cognitive focus (from conscious focused mode to day-dreamy imagination mode), a “micro” respite from the task at hand.  This process allows us to “reboot” and refocus!

Do women blink more than men?

When I mentioned to my husband that I was writing this blog on blinking he said “Oh, do you mean how women blink more often than men?”  I went off, a little indignant to double check, and I am happy to report that this one is a myth.  There is no discrimination between the sexes on blinking rate.  Other factors, such as fatigue, environment and medication can of course effect how often we blink.

Blinking and social cues?

Although we tend to blink unconsciously we do still follow certain social cues or natural pauses. An interesting study observing an audience watching a short video found that they synchronized their blinking to occur at points in the video that required less attention or where they were less likely to miss something of importance.

During social conversation we are more likely to time our blinking with pauses in speech, both for the person talking and, a second or two later, the person listening.

The frequency of blinking also depends on the particular type of social interaction and the emotional state of the person.  Blink rate tends to increase after a lie has been told, for example, but remains unchanged when telling the truth.  Stress, anger and anxiety also increase blink rate.  People suffering from depression have exhibited faster blink rates as well as those with certain mental health issues.

What about blinking in other animals?

Some animals (such as the tortoise) blink their eyes independently of each other. Some have a very slow blink rate (such as cats and rabbits).When birds blink their lower eye lid comes up to meet the upper lid, in mammals it is the reverse.An interesting study conducted on the blink behaviour of 71 different species of primates reported a correlation between primate size and increased blink rate.  Of even more interest was the observation that blink rate increased in species that lived in larger greater group sizes and experienced more social interaction.

 Blinking and Art…

I came across an interesting reference to blinking while writing this blog that I thought it was worth sharing.   It refers to the famous Mona Lisa painting by Leonardo da Vinci.  The enigmatic face of Lisa Gherardini captured on the canvas has lead to centuries of speculation as to the secret behind her smile.  It appears that da Vinci used a layering and blurring technique that causes our eyes to re-adjust every time we blink, thus restarting the puzzling scrutiny of that mysterious expression.
The Mona Lisa – image source Wiki Commons
Sticky toes

Sticky toes

We are amassing quite a collection of geckos around our house these days.  Not the organic variety of course, although that would really please the kids!  No, our collection consists of ornaments, wall hangings, trinkets and even jewellery.  It all started ten years ago when on honeymoon in Barcelona … the little guys were everywhere and we were drawn to them with fascination – especially their ability to scale any surfaces they encountered (even glass).  So the collection started from there, anytime we come across a quirky gecko decoration or ornament we like, we purchase and add it to the collection!


Ten years on and our fascination has grown along with our collection.  I was delighted to show my children a recent photo from National Geographic of a gecko.  Of course that lead to the children asking questions, that lead to questions, that led to the ultimate… “How do they walk up walls?” After answering their questions I decided this might be a good topic to start my 2013 blog with.  So…how do these amazing little creatures manage their “spiderman-like” feats? It truly is a marvel of nature but before I delve into that, I want to tell you a few other quirky facts about these lovely little creatures.

Geckos are a type of lizard.  They are found on all continents except Antartica.  They come in many shapes and sizes and are in fact the most species rich order among lizards.  They are also among the most colourful lizards in the world.

Most species of geckos can actually sever part of their tail, usually to escape the hold of a predatory or threat.  The released tail segment can keep wriggling as a distraction while the gecko escapes.  PRETTY COOL DON’T YOU THINK?  This process of severing the tail is called caudal autotomy!

photo credit: Tambako the Jaguar via photopin cc
photo credit: Tambako the Jaguar via photopin cc

Another very interesting fact about geckos is that nearly all species of geckos have no eye lids and can therefore not blink. Instead, they use their long tongues to clean any dust from their eyes.

Already you can begin to see how fascinating these creatures are, and that is before we have even looked at their ability to apparently defy gravity! DID YOU KNOW THAT A GECKO CAN SUPPORT ITS ENTIRE BODY WEIGHT ON ONE TOE?

So here is the science bit behind HOW THEY DO IT…the toes of a gecko are covered in hundreds of small ridges called lamellae.  Each ridge is covered in millions of hairs called setae.  Setae are much thinner that human hair (up to 30 times thinner).  Each seta then splits at the top into tiny strands called spatulae – there can be up to 1000 spatulae on one seta (if you think you have problems with split ends, pity the poor gecko!).  So you can begin to imagine how tiny these spatulae are, in fact, they are so tiny that they can bond with the molecules of the surface they are touching.  This bonding is referred to as van der Waals interaction!   The great thing about it is that it is what is called dry adhesion – it doesn’t require any sticky compounds or leave any messy residue.

photo credit: bernat... via photopin cc
photo credit: bernat… via photopin cc


This gives us an idea of how the gecko sticks to the surface, but HOW DOES IT UNSTICK?  The adhesion (sticking) process is said to be one-directional…imagine sticking a piece of sticky tape to a surface and then taking hold of one edge and peeling it back to remove it… the gecko does something similar.  Geckos toes bend in the opposite direction to humans so they can “peel” their toes off the surface from the tip backwards.  Add to this the fact that geckos have rotating ankles and you start to understand how they can move in any direction.

As you can imagine this ability has captured the interest of Scientist for a long time.  Imagine if we could copy this adhesion from the gecko… what could we do with the technology??? Robots that can scale any surface would be great in extreme or rescue situations, right?  Or how about a suit we could wear to allow us to climb like a gecko? Did you know that geckos can climb in a vacuum? So now we can start thinking about using this technology in space!  Or how about using the technology in bandages – inspired by the observation that geckos can climb in wet conditions… a bandage that stays on when wet.

Maybe YOU can think of another novel way to use gecko technology?  If you have any ideas I’d love to hear them!

More on geckos…
Nat Geo Kids Creature Facts – Geckos
The dance of the disembodied gecko tail
Geckos evolved sticky feet many times