The information is sent by afferent nerves to the brain the thalamus and eventually to the cortex , where we recognize the taste as either pleasant or unpleasant. Interestingly, our mood can affect our sense of taste, explaining various appetite changes associated with mood disorders.
As with sight and sound, taste is dependent on smell. If you cannot smell, like when you have congested sinuses, food will taste bland. Our brain uses signals from our eyes, nose and mouth when we eat, so when one of those signals is missing, our brain can have difficulty differentiating what we are eating.
When you breathe in through your nose, olfactory receptors are stimulated by chemical molecules suspended in the air, and messages are sent to the olfactory bulb at the base of the brain. Smell is the sense most strongly linked to memory. For example, smelling apple pie can trigger a happy memory from childhood. In fact, smelling an odor while experiencing something helps recent memories get recorded into permanent storage. Our skin's three layers, the epidermis, dermis and hypodermis, are made up of millions or sense receptors.
Once stimulated by touch, these receptors trigger nerve impulses that communicate with the somatosensory cortex of the brain, relaying information about temperature, pressure and pain.
Sensory receptors encode information about everything skin comes in contact with. Neurotransmitters, or brain chemicals, are released into our body, giving us the sensations or feelings.
The sense of touch is so important to humans that a lack of touch can lead to physical and behavioral problems, improper brain development, and even death. Updated April 24, Read the following quote out loud:. Notice anything odd while you were reading the text in the triangle? We know this. In other words, your past experience has changed the way you perceive the writing in the triangle!
A beginning reader—one who is using a bottom-up approach by carefully attending to each piece—would be less likely to make this error. When a stimulus is constant and unchanging, we experience sensory adaptation. This occurs because if a stimulus does not change, our receptors quit responding to it. A great example of this occurs when we leave the radio on in our car after we park it at home for the night.
When we listen to the radio on the way home from work the volume seems reasonable. However, the next morning when we start the car, we might be startled by how loud the radio is. What happened? We adapted to the constant stimulus the radio volume over the course of the previous day and increased the volume at various times.
Now that we have introduced some basic sensory principles, let us take on each one of our fascinating senses individually. Vision is a tricky matter. When we see a pizza, a feather, or a hammer, we are actually seeing light bounce off that object and into our eye. Light enters the eye through the pupil, a tiny opening behind the cornea.
The pupil regulates the amount of light entering the eye by contracting getting smaller in bright light and dilating getting larger in dimmer light. Once past the pupil, light passes through the lens, which focuses an image on a thin layer of cells in the back of the eye, called the retina. Because we have two eyes in different locations, the image focused on each retina is from a slightly different angle binocular disparity , providing us with our perception of 3D space binocular vision. You can appreciate this by holding a pen in your hand, extending your arm in front of your face, and looking at the pen while closing each eye in turn.
Pay attention to the apparent position of the pen relative to objects in the background. Depending on which eye is open, the pen appears to jump back and forth! This is how video game manufacturers create the perception of 3D without special glasses; two slightly different images are presented on top of one another.
It is in the retina that light is transduced, or converted into electrical signals, by specialized cells called photoreceptors. The retina contains two main kinds of photoreceptors: rods and cones. Rods are primarily responsible for our ability to see in dim light conditions, such as during the night.
Cones, on the other hand, provide us with the ability to see color and fine detail when the light is brighter. Rods and cones differ in their distribution across the retina, with the highest concentration of cones found in the fovea the central region of focus , and rods dominating the periphery see Figure 2.
Next, the electrical signal is sent through a layer of cells in the retina, eventually traveling down the optic nerve. Information is then sent to a variety of different areas of the cortex for more complex processing. Some of these cortical regions are fairly specialized—for example, for processing faces fusiform face area and body parts extrastriate body area. Damage to these areas of the cortex can potentially result in a specific kind of agnosia , whereby a person loses the ability to perceive visual stimuli.
A great example of this is illustrated in the writing of famous neurologist Dr. Oliver Sacks; he experienced prosopagnosia , the inability to recognize faces. Humans have the ability to adapt to changes in light conditions. As mentioned before, rods are primarily involved in our ability to see in dim light.
They are the photoreceptors responsible for allowing us to see in a dark room. You might notice that this night vision ability takes around 10 minutes to turn on, a process called dark adaptation. This is because our rods become bleached in normal light conditions and require time to recover. We experience the opposite effect when we leave a dark movie theatre and head out into the afternoon sun. During light adaptation , a large number of rods and cones are bleached at once, causing us to be blinded for a few seconds.
Light adaptation happens almost instantly compared with dark adaptation. Interestingly, some people think pirates wore a patch over one eye in order to keep it adapted to the dark while the other was adapted to the light. Our cones allow us to see details in normal light conditions, as well as color. We have cones that respond preferentially, not exclusively, for red, green and blue Svaetichin, This trichromatic theory is not new; it dates back to the early 19th century Young, ; Von Helmholtz, This theory, however, does not explain the odd effect that occurs when we look at a white wall after staring at a picture for around 30 seconds.
Try this: stare at the image of the flag in Figure 3 for 30 seconds and then immediately look at a sheet of white paper or a wall. According to the trichromatic theory of color vision, you should see white when you do that. Is that what you experienced? This is where the opponent-process theory comes in Hering, This theory states that our cones send information to retinal ganglion cells that respond to pairs of colors red-green, blue-yellow, black-white.
These specialized cells take information from the cones and compute the difference between the two colors—a process that explains why we cannot see reddish-green or bluish-yellow, as well as why we see afterimages.
Color deficient vision can result from issues with the cones or retinal ganglion cells involved in color vision. Some of the most well-known celebrities and top earners in the world are musicians. Our worship of musicians may seem silly when you consider that all they are doing is vibrating the air a certain way to create sound waves , the physical stimulus for audition.
First, one may argue that vision is by nature easier or that the other senses are by nature harder to investigate. In contrast, it seems hard to imagine how there could be off-the shelf technology for studying the chemical senses, for instance: Although researchers have tried to, no one has yet found a digital way of stimulating the chemical senses, which would be an important precondition for setting up standardized and easily controllable experiments see Spence et al. The same can be said about haptic long-term memory: Whoever wants to study the haptic exploration of everyday objects will have to collect the respective objects.
There seems to be no way around this. Even if there is a way around this in some cases, however, the tools developed to study other senses such as touch see e. Rather than demonstrating that present-day technology used to investigate haptics is equal to the technology to investigate vision, these efforts to create adequate instruments in the absence of an established technology remind of the situation at the end of the 19th century, when the first experimental psychological laboratories were founded see e.
At that time, creating tools for research on vision was a laborious process. Hence, one can get the impression that the development of haptic technology lags behind in time. Thus, one could hypothesize that instead of or at least in addition to being naturally better suited for investigation, vision may have had an arbitrary advantage in the beginning of experimental research and that this initial advantage has perpetuated and possibly even reinforced itself since then.
Classen et al. Expressed differently, funding for research into vision might be much easier to obtain than funding for smell or touch. This might in turn bias researches toward doing research on vision as it is easier to get funding, and so on. There are various possible reasons why the study of vision may have had an advantage in the beginning of experimental research: 1 researchers at the time may have had personal reasons to study vision instead of other modalities e. In conclusion, the methodological-structural explanation claims that there is more research on vision because the available, present-day technology is better suited for studying vision than for studying other modalities.
Although one may claim that vision is easier to investigate by nature, it seems quite likely that this claim and thus the technological advantage for vision is at least partially the result of a Matthew effect: As there is more research on and easier accessible technology for vision compared to other modalities today, there will most likely be more research on and technology for vision tomorrow. In addition to the self-perpetuating process proposed by the Matthew effect, there may also be a cultural explanation for the bias toward vision.
At first sight, one may think of visual dominance as a cultural constant that can be traced back to antiquity for a history of the senses, see e. In a similar manner, Aristotle creates a ranking of the senses, putting vision first, followed by hearing, smell, taste, and touch.
Although subsequent philosophers did not agree with the classical Aristotelian hierarchy in every respect, vision is almost always ranked as the highest sense in Western societies throughout the medieval ages up until today. In this context, it is especially interesting that the study on the frequency of words referring to the different sensory modalities quoted above, did not only find an overall higher frequency of visual words in the investigated English corpora.
When looking at the average frequencies for each modality based on the ten most exclusive words per modality, there was hardly any change in the past years see Winter et al. Although the Aristotelian hierarchy has undeniably had a huge influence on the conceptualizations of generation upon generation of philosophers and although one may argue that there is a long history of visual dominance, matters become vastly more complicated when taking a closer look at the available sources.
Thus, one could claim that the hierarchy proclaimed by Aristotle was not meant to be interpreted that strictly after all. Second, it can be demonstrated that the dominance of the visual — supposedly already existing in the times of Aristotle — was less pronounced for a long time, that is, that the non-visual senses have lost ground against sight in the course of the past centuries.
Hence, rather than being a cultural constant, visual dominance turns out to be heavily influenced by human decision-making.
I will illustrate this idea using three different examples. First, consider the shift from an oral, hearing-dominated to a written, sight-dominated culture e. Note, that this shift from hearing to sight arguably also changed interactions between people: The oral transmission of knowledge — and of literature, by the way — requires at least two people a teacher and a student; someone who is telling a story and someone who is listening to it ; in contrast, reading a book does not require any personal interaction — you can do it entirely on your own.
Second, take the decrease of the importance of smell. Moreover, the strength of the odor of a plant was associated with its presumed medical power: In order to protect themselves against epidemic diseases such as the plague, people in the medieval ages often carried a pomander with them, as they believed that strong scents are an antidote against the odors of illness which were considered to be the cause of infection.
This slowly changed from the 16th and even more so from the 18th century onward: As the belief in the healing power of scents faded away and as gardens were also cultivated for aesthetical and recreational reasons, visuals became increasingly more important.
In contrast to this hypothesis, it has been shown that the olfactory abilities of humans are in fact quite good. Third, imagine walking through a modern museum exhibiting sculptures: You would probably not in your wildest dreams think of touching these sculptures — and if you did, security guards, alarms, not to-be-crossed lines on the floor or transparent cases around the sculptures would remind you immediately that art is not to be touched see Gallace and Spence, , for the few contemporary counterexamples.
Note, that remnants of these haptic worshipping traditions have survived until today: The right foot of the bronze statue of St. Peter in the St. As these three examples demonstrate, one can trace an ongoing shift toward vision throughout history. However, the bias toward vision may be even more pronounced in our present-day societies than ever before: Beginning with the invention of movies, cinema, and television and even more so in the face of the omnipresence of smartphones and computers, visual technologies increasingly regulate our daily lives:.
Modern life takes place onscreen. It is not just a part of everyday life, it is everyday life Mirzoeff, , p. To give one illustrative example, consider the now-common habit of taking a picture of your meal and of sharing it on social media before starting to eat.
It has been hypothesized that this habit has profoundly changed the way restaurants are recommended. This may ultimately lead chefs and restaurant owners to pay more attention to the visual arrangement of the food they serve, or even to prepare the food in a way that is going to look good on Instagram see e.
More broadly speaking, paying attention to visual aspects seems crucial to achieve important goals in life such as finding a job or a partner as well as improving social relationships — just think of the importance of visuals when presenting oneself on an online dating website, sharing holiday pictures on social media or applying for a job with a well-designed resume.
Such a visual turn can supposedly have a double function: it can account for the dominance of the visual by emphasizing the importance of research on the topic and it can help to create both an appropriate methodology to investigate and appropriate theories to describe the visual turn.
Overall, it seems that the dominance of the visual is not a cultural constant. It should not be forgotten, however, that everything that has been discussed so far primarily referred to — pre-modern, modern, and postmodern — Western cultures and societies.
As it will turn out, considering non-Western societies only confirms the ideas presented so far: The dominance of the visual is at least partially the result of human decision-making and should thus not be regarded as an unvarying historical constant. Two examples shall suffice to illustrate the enormous cross-cultural variability.
First, a recent study has demonstrated that there is no universal hierarchy of the senses by investigating 20 different languages including three unrelated sign languages Majid et al. The authors created stimulus sets for each of the five Aristotelian sensory modalities and asked their participants to describe them What color is this? What sound is this? Apart from the fact that smell is poorly coded in most languages, there was no common hierarchy of the senses.
While English indeed seems to have a visual bias see the study by Winter et al. Second, let us examine one of the cultures for which sound seems to be more important than vision: the culture of the Songhay of Niger.
It is important to note, that for them, sound is not only important because like in any oral culture, knowledge is transmitted by spoken words, but because the sounds of the words themselves are believed to carry energy and power:.
What can we learn from considering the cultural explanation regarding the question why there is so much more research on vision than on any other sensory modality? The answer is quite simple: Living in a visual society means living in a society placing high value on vision and comparably little value on the other senses — a tendency that is mirrored in the number of studies on vision. Put differently, a society placing higher value on the other senses would probably develop more balanced research agendas i.
This paper has discussed three different explanations. The only explanation that can be found in contemporary books on perception and cognitive psychology, which I have called the textbook explanation, claims that the reason for the bias toward vision is its importance and complexity. Although there are arguments in favor of this explanation, the validity of these arguments seems debatable as it crucially depends on the definition of importance and complexity.
Apart from that, the textbook explanation is at least incomplete as there are other aspects that need to be taken into consideration. As the methodological-structural explanation proposes, the present-day technology is better suited for studying vision than for studying other modalities, which may be the result of a Matthew effect reinforcing the advantage of the visual.
In addition to that, the cultural explanation suggests that the dominance of the visual is not an historical constant, neither in Western nor in non-Western societies, and should consequently be viewed as being influenced by human decision-making. In my opinion, there a two important lessons to be learned from this outcome: the necessity of diversity and the necessity of integration.
Let us consider both. First, the necessity of diversity: Diversity is not necessarily good per se. In the event that there was in fact one modality, which is much more important and complex than all the others, a research bias toward this modality would be perfectly understandable and a visual turn advisable.
This is not only because the other senses deserve more attention, but also because the theories of perception and perceptual memory developed from studies on vision may in fact be theories on visual perception and visual memory, which do not capture the peculiarities of the other senses see e. Thus, basing our theories of perception and perceptual memory mainly on vision may indeed lead to limited and impoverished conceptualizations of perceptual memory.
Second, the necessity of integration: Although I have not explicitly stated this, the ideas presented in the present paper were by and large in line with the Aristotelian view that humans possess five senses. No more than the hierarchy of the senses, however, the number of postulated senses is the same across times and cultures see e. Given that the different sensory modalities share significant parts of their neural underpinnings, given that the processing of information seems to be rather multimodal than unimodal, and given that our everyday experience is characterized by the concurrent stimulation of our senses, investigating their interactions seems more promising than trying to make more and more fine-grained distinctions for the attempt to say more about the different kinds of interactions between the senses see e.
Indeed, it has been shown that the integration and combination of the senses can have an important impact on educational outcomes see e. All in all, investigating the seemingly easy to answer question as to why there is so much more research on vision than on any other sensory modality does not only lead us right into the middle of historical changes and cultural differences, but also gives us the opportunity to take a step back and to start thinking about visual dominance.
If the degree to which vision dominates research on the different sensory modalities is not an unchangeable necessity, what kind of sensory environments do we want to create and what kind of research do we want to conduct?
Ethical review and approval was not required for the study on human participants in accordance with the local legislation and institutional requirements. The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
I would like to thank Felix Hutmacher and Leonard Shapiro as well as the reviewers for their helpful comments and suggestions. Alais, D. Multisensory processing in review: from physiology to behaviour. Seeing Perceiving 23, 3— Alloa, E. Iconic turn: a plea for three turns of the screw. Theory Crit. Axel, R. The molecular logic of smell.
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