Monday, 28 January 2013

A DOGS FIVE SENSES


If we were to think of our brains as computers we can imagine them receiving and processing data received typically from a keyboard. This data is then analysed and an output is produced either to a screen or a hard copy like a print out. Our brains receive input not through a keyboard but through our senses of which we have five. Touch, taste, hearing, seeing and smell. The sensory data received travels up through our cerebral cortex to our brains which then analyse the input and produce an output which it sends back again.In Stanley Coren’s book “How dogs think” he writes about the Greek philosopher Protagoras who summed up this notion around 450 BC by saying “we are nothing but a bundle of sensations”. Dogs share the same five senses as man. Both man and dog translate the sensory information the same way, but with noticeable differences.
The quality of the information received by man and dog is different, and that is what separates us when we compare sensory input.

Man has known for thousands of years that dogs possess abilities that are far more sophisticated than man. This is evident in how man has harnessed those abilities for their own use in work and play. Dogs have been taught to herd, guard, protect, scent, retrieve, attack and in times of war send messages for us. As mans needs have evolved dogs abilities have evolved also. Nowadays we use dogs to search and rescue in areas of avalanches or earthquakes for people. For drugs and explosives and lately to even detect cancer in people. All of this using the dogs remarkable senses. In our efforts to better understand dogs we have first understand how they perceive and respond to the world around them. To some extent this has been done for some of the senses. For example we know that dogs do not see the spectrum of colours that humans do. Much like human colour blindness, dogs are red and green colour blind. They see rudimentary colours not just shades of grey. Trying to understand some of the other senses though is not as simple. Bruce Fogle in his book “The Dog’s Mind” writes “it’s almost impossible to ever appreciate the awesome capacity of the dog to differentiate thousands of different odors”. He goes onto say “we humans can only really use our own capacities for terms of reference and it is this massive restriction that inhibits us from really understanding how sensory input touching, smelling, tasting, seeing and hearing affects the dogs behaviour.

The five senses.
As discussed previously, a dog’s sense of smell is far more sophisticated than that of man’s. Here are some facts taken from Bruce Fogle’s book “The Dogs Mind”.
*   The average dog has 220 million scent receptors in his nose.
*   Humans have 5 million.
*   If the membranes lining the inside of a dogs nose were laid out flat, the total surface area of those membranes would be far greater than the total surface area of the dog’s entire body.
*   The average dog has seven square metres of nasal membrane.
*   Humans have about half a metre and we are usually bigger
*   The average dog has such acutely sensitive scenting ability that it can detect and identify smells that are so dilute that even the most sensitive of scientific instruments cannot measure them”.

Smell is the dominant sense in a dog, a large part of the dogs brain is devoted to analyzing odors. A dog has two olfactory bulbs attached to the brain which are used to decode every smell they encounter. The bulbs themselves weigh 60 grams. In comparison a humans olfactory bulbs weigh just 15 grams. Compare that to the size of brains in both man and dog, a humans brain is on average ten times the size of a dogs, means the dog has forty times as much of its brain dedicated to smelling as we do. Dogs have mobile nostrils which they can use independently. They do this sometimes to establish in which direction a scent is coming from. A dog also has an amazing sniff. Scent particles get trapped in nasal passageways when a dog sniffs. These particles get converted into electrical signals which go up to the cerebral cortex and the limbic system which controls dogs emotions. The action of sniffing interrupts the dogs natural breathing action which can be a bit of problem when rescue dogs are working in a hot climate. Dogs will pant when hot and if the dog is panting it will affect its ability to sniff and collect scent particles. When search teams are using dogs to find people trapped in places were there has been an earthquake, they will take lots of rest periods and work the dogs for a smaller amount of time than normal. Although dogs in general have good scent detection.\selective breeding has meant certain breeds of dogs have been selectively bred to enhance the scent detection qualities in dogs. The Beagle, Bassett and Bloodhound are examples of breeds which have been bred for their scent detection abilities. A dogs nose was initially evolved to help them hunt. The dogs ability to not only detect its prey through scent, but the direction and species that left the scent were extremely important. Dogs differ from humans not only in their ability to sense smell particles far smaller than humans can detect, but also their scent discrimination powers are fantastic. It can be likened to a humans ability to differentiate objects by sight. In Stanley Coren's book "How dogs think". He writes, "Imagine a quilt with a bright colourful flowery pattern, on top of which we throw a flashlight, a hammer, a pen and a book. The task of finding, identifying and separating these objects using our visual processing system is really quite simple for humans".

According to Bruce Fogel in his book "A Dogs mind", Touch is the first and most important senses that a puppy develops. He writes in his book that research carried out by Dr. Y. Zotterman of the Swedish research council concluded that pups have infra red sensors in their muzzles which even when they are blind and deaf can lead puppies back to their mothers. And it is touch - contact comfort - that not only soothes the pup but is very important in developing a mature and sensible mind in a dog. According to Bruce Fogel dogs'' who are deprived of touch "will grow to become subordinate, fearful and withdrawn." The importance of touch continues throughout a dogs life. It is well know that stroking a dog not only reduces the heart rate and blood pressure of the dog, but it actually has a similar effect on its owner who it has formed an attachment with. We have a female lab called Tess who we have trained as a Therapet. My wife is a member of Canine Concern and visits a local old folks home with Tess. There the patients appear to get some happiness when Tess site and allows them to stroke and pet her. The fact that she gets the odd biscuit doesn't go wrong either. Although humans have the sense of touch also, dogs differ from humans because dogs have a set of scent receptors that humans dont have, Whiskers. Men do have whiskers but they are largely unfunctional. The dogs whiskers are very important and provide an early warning to the dog like a proximity sensor. Whiskers let a dog know when it is close to bumping into the door or chair. It also prevents damage to the eyes from flying objects, by warning the dog to close its eyes or turn its head. In Stanley Corens book "A Dogs Mind" he uses the example where if you tap a dogs whisker his eye will blink on the same side you tap his whisker. The comfort dogs get from touch can not only be from the pups mother but as mentioned earlier even later in the dogs life dogs can get comfort from a humans touch. There are different types of touching methods and in the book The Dogs Mind, Stanley Coren describes a touch method which was developed by Linda Tellington-Jones. This method was more of a massage than just merely a touch. However this massage procedure was used to reduce tension and anxiety and was called The Tellington Touch or T-Touch.

I drive a pick up truck, which has a diesel engine. My wife tells me that if she is home before me she can tell when i am minutes from the drive because our dogs get up and start to pace back and forth firstly at the back door and then they collectively move to the front door. I live in a suburb and our house is surrounded by other houses and vehicles come and go at tea time. But my wife tells me that no matter how many cars or vans pass our door, they only get 'excited' just before i come through the door, maybe five minutes before. We have always thought that they could distinguish between the various car sounds. I used to say it was because i drove a diesel and it was probably because it was so noisy compared to petrol cars. I also thought initially it was a timing thing, as I usually finished work at the same time every day. But my wife would tell me, even those days were I worked late, the dogs would not get up until five minutes before I walked through the door. Stanley Coren writes that this "is evidence of the acute sense of hearing that a dogs has relative to humans - at least for certain types of sounds." Another ability that dogs have over humans is their ability to move their ears independently in the direction of incoming sound waves. This allows dogs to pin point the direction of where the sound is coming from. Northern Timber wolves use this ability to seek out small mammals like mice and voles, which is a main part of their diet. These small mammals make a high pitched squealing sound. Humans can hear sounds that typically fall into the range between 1'000 and 2'000 Hz. We can hear sounds that reach 20'000 Hz, however dogs can hear sounds upto 65'000 Hz. Typically they normally hear sounds 4'000Hz. By being able to hear these high pitched sounds and twisting their ears to pick up which direction they are coming from, makes them prolific hunters. Pitch discrimination was first researched by Pavlov, who wrote that dogs can distinguish tones differing by only one eighth of a tone. Which is why my dogs are good at recognising the sound of my car engine.

In a scene from the movie 'Jurassic Park', Sam Neil is in a scene with Jeff Goldblum where the main character of the film the T-Rex is on the rampage and attacking everything in sight. Sam Neil shouts to Jeff Goldblum not to move as the T-Rex hunts by motion detection. Dogs sight has similar characteristics to this hollywood computer generated beast. Great motion detection, great distance vision but cant see the nose at the end of their faces. This is where we differ from our canine partners. Bruce Fogel writes in his book "The Dogs Mind" Although the dogs is perhaps ten times more sensitive to peripheral movement, he has poor vision up close, though reasonably good vision at a distance. Dogs have more flattened eyes than humans. They can change the shape of their lenses and can alter the focal length, but not as well as humans. Dogs eyes are more light sensitive than humans and can see better in low light but not in total darkness. Not all dogs eyes are placed in their skulls in the same way.

It was once thought that dogs were “color-blind” – only able to see shades of black and white with some grey, but scientific studies have found that’s not true. Dogs can see in color – ranging from blues and greens to greys and crèmes, and of course, black and white. It’s been estimated that humans can distinguish somewhere between 7 and 10 million different colors. Dogs have an additional reflective layer in the eye called the tapetum lucidum, which reflects light back into the receptor cells of the eye, which not only increases their night vision, but gives them that spooky appearance of eyes glowing in the dark.

Taste is the only other sense that is present at the birth of the puppy. Taste is very closely associated with smell. Dogs dont have as good a sense of taste as humans. Humans are reported to have 9000 taste buds in their tongues, whilst dogs have only 1700 approximately. Furthermore dogs dont have the same variation in their taste recognition processes. Where we humans wont eat anything that smells badly, to dogs the smellier the better. Dogs tend to be more concerned with smell than taste. They also have a reflex vomitting action which they do when they eat something that does not agree with them. They will gobble down food as fast as possible, hardly pausing to taste it. Of all the senses the sense of taste is a dogs least developed.

From the research I have done I would say that from the dogs point of view, the dogs most important sense is a split decision. From a well being stand point I would have to say that touch is a dogs most important sense. As described before a comforting touch can reduce a dogs heart rate, blood pressure and anxiety. Humans also benefit from petting or stroking a dog getting much the same benefits. as we all know reducing stress and anxiety can lead to healthier happy lives, who doesn't want that? But smell is also very important for dogs and is probably their most prolific sense. In the wild their ability to scent danger or prey is key to any dog/wolves continued survival. From a humans perspective, smell is undoubtedly the sense that humans most use in a dog. From helping to search for survivors, to seek out bomb making materials, they are now even ably to detect certain types of cancer better than a mass spectrometer. Their capacity to differentiate thousands of different odours is something we can truly never understand. Humans have put dogs superior senses to use for his own benefit and gain. In conclusion, studying the dogs senses is important in allowing us to understand how they communicate. A dogs idea of its environment must be very different from ours, dogs rely mostly on their sense of smell and hearing whilst we are more visually biased. as Protagoras the Greek philosopher put it "we are nothing but a bundle of sensations".