Author: John M. Henshaw
ISBN: 13: 978-1-4214-0436-3
APA Style Citation
Henshaw, John M. (2014). A Tour of the Senses: How Your Brain Interprets the World. Baltimore: Johns Hopkins University Press.
Often, one of the most difficult units in an introductory psychology course is sensation and perception. A Tour of the Senses provides an excellent source of supplemental materials to accompany this portion of the psychology curriculum. This highly engaging book offers detailed explanations of difficult concepts, interesting stories, current and historical research, and simple classroom appropriate demonstrations for each of the senses. The author, John M. Henshaw is a department chair and professor of mechanical engineering at the University of Tulsa. Because A Tour of the Senses is written by an engineering professor, it provides excellent insight into the field of human factors psychology. The book is divided into three main parts: Stimulus, Sensation, and Perception and covers all of the various senses in exceptional detail.
The section on stimuli is divided into electromagnetic stimuli, chemical stimuli, mechanical stimuli, and the overall science of sensation. In each of these sections, the author provides explanations of the various types of stimuli that reach our sensory receptors. There are also many interesting accounts of how stimuli are received and perceived differently by other species as well as remarkable cases of humans using senses typically associated with other organisms. The wide range of animal senses, which differ from human senses in both type and range of ability is examined in the book. Detailed accounts of the unique abilities of certain organisms such as echolocating bats, ultraviolet radiation sensing honeybees, and snakes that can detect heat waves would all be interesting topics for discussion at the beginning of the sensation unit. The most unusual animal sense discussed is that of the narwhal, a type of whale with a long, slender, conical shaped tusk reaching up to 9 feet in length. Although there have been many theories throughout history as to the purpose of this unique appendage (icebreaking, fishing, weapon), the actual answer is even more bizarre. The tusk is, in fact, the left front tooth of the animal. The tusk tooth, which is covered with nerve endings, is a sense organ likely capable of detecting changes in the saltiness, temperature changes and pressure changes in the water.
The opening section details the remarkable story of Ben Underwood, a blind young man who taught himself to see using echolocation. There are many short videos on Ben’s case available online (see additional resources). There are also exceptional descriptions of difficult concepts such as additive and subtractive color mixing and the just noticeable difference. An interesting aspect of this section is the detailed attention the author gives to the stimuli responsible for senses such as olfaction, gustation, vestibular, proprioception, which unlike vision and audition are often not given much attention in introductory psychology textbooks.
The large section on sensation focuses on how the different sensory organs in humans and other animals have evolved to take in information from the environment. The process of transduction for each of the sense is discussed in detail, including how the information travels from the sense organs as an electrical signal to various areas of the brain responsible for perception. The vision section provides a simple demo for illustrating the limited range of the fovea that each student could do individually. Students should place a quarter over the words on a page so that they can read the lettering above George Washington’s head. Have students focus on the quarter and without moving their eyes attempt to read the words on either side of the coin. Typically, it is difficult to identify more than a word or two on either side of the coin due to the limited range of foveal vision. Although they will be aware of words, they will not be able to read them if they are truly focusing on the quarter.
The importance of visual acuity in relationship to professional athletics is discussed, highlighting how much this sense is responsible for success at the highest levels. In golf, where athletes can enjoy a much longer career span, declines in vision often lead to the end of a career. Many top golfers such as Tiger Woods and Vijay Singh have had laser eye surgery to increase their visual acuity to twenty-fifteen or better to improve their putting ability. In other sports such as baseball, tennis, and football exceptional vision is often one of the aspects that separate the best in the sport from others. In recent years, more and more top athletes have begun incorporating eye exercises to train the muscles that control eye movement.
The chemical senses are explored in great detail and also include various disorders related to problems with smell and taste. The taste section includes demos and detailed information about supertasters, sensory interaction, and the history of the search for an effective sugar substitute. Anosmia or the complete absence of smell is likely present in 2 million Americans. The loss of smell that occurs as part of the aging process is called Presbyosmia. Some individuals experience an overly sensitive sense of smell (hyperosmia) and others with parosmia sense as unpleasant what many others perceive to be pleasing scents. The use of dogs and other animals whose sense of smell is greater than humans is explored in terms of how animals have been successfully trained to find explosives, bodies, and drugs. Dogs have been trained to complete “dog-scent lineups” which may be used in court.
The book refers to audition, touch, pain, temperature, balance, and bodily awareness (kinesthesis) as mechanical senses because these are generally activated by the energy of motion or kinetic energy. Audition, on the other hand, involves the transduction of vibrating (motion) air molecules, balance and body position are connected to the movement of the head and body, and the sense of touch typically involves the movement of one surface over another. The most detailed section relates to hearing, and the book examines the structure of the inner ear from an engineering perspective. There are also excellent explanations for various types of hearing loss and solutions designed to assist individuals with these disabilities. As in other areas of the book, examples of animals with exceptional sensory abilities are examined to find ways to engineer artificial senses for human use. Research regarding touch and pressure sensation has led to advances in robotics including surgical applications.
The vestibular sense is especially quick at interpreting the position of the head. If you shake your head from side to side while reading this text, you are still easily able to focus on the words and read the material due to what is called the vestibular-ocular reflex. The vestibular-ocular reflex is a sophisticated coordination between the vestibular sense and the muscles that position the eyes. If you keep your head and eyes stationary and move the book from side to side, however, you will not be able to read the text as well. Just as there are hearing and vision tests given by doctors, there are also tests for the vestibular sense. Doctors examine patients for balance related problems by using the “rapid head impulse test” explained in the book. One of the most interesting sections is how sensory illusions can impact pilots. As a result of these common illusions, pilots must trust their instruments because their perception has been disrupted by errors in vestibular perception. Problems with proprioception are rare but also possible. Without proprioception, no movement can ever be automatic, and even simple actions such as sitting up, walking, or holding a cup become incredibly difficult.
The final section of the book details how perception occurs in the brain including various examples of perception problems due to problems in the brain as opposed to problems in sensory organs. There are methods for enhancing or replacing human sense organs and sending information directly to the brain. One of the first perceptual issues discussed is the problem with recognizing faces. Some people are exceptionally good at remembering faces, and other have little or no ability in this area. Those who are very skilled at facial recognition are sometimes referred to as super-recognizers. On the lower end of the curve is a condition called prosopagnosia or “face blindness” in which individuals have difficulty recognizing faces including friends, family, or even their own face. Prosopagnosia may be present from birth or acquired as a result of damage to the area of the brain that specializes in facial recognition. Individuals with face blindness may need to use the less sensitive object recognition systems in the brain. Face blindness is estimated to impact approximately 2% of the population with more than 6 million individuals experiencing dramatic impairment. Also, some individuals suffer from an even less well-understood condition called phonagnosia, which is essentially the sound equivalent of face blindness. For example, these individuals can identify general features of a voice on the phone (e.g. gender, age, pitch, accent) and can understand what is being said, but do not recognize the person who is speaking even if it is a close friend or family member. Phonagnosia involves a perceptual problem specifically related to damage in the areas of the brain responsible for processing voice recognition of familiar people.
The author provides a detailed section differentiating between bottom-up and top-down processing including several examples and demonstrations. Bottom-up processing occurs when the brain takes unfiltered signals received from sensory receptors and breaks them down into individual packets of information. Top-down processing, on the other hand, involves the process by which the brain applies meaning to the information it receives by using background knowledge and experience to interpret the information. A part of top-down processing involves filling in missing pieces of information to create complete perceptions, which is referred to as perceptual completion. There are also auditory examples of perceptual completion.
A Tour of the Senses is a fun, easy to read book that provides a great deal of background information on the area of sensation and perception. As an engineer, the author describes the human sensory perception system but also discusses exceptional sensory abilities in other animals and the technology involved in enhancing human sensory capabilities. The book is an engaging combination of personal examples, unique stories, research, and practical applications for sensation and perception research.
Other Related Resources
Video documentary about Ben Underwood, a blind teenager who taught himself to see using echolocation
Warning: A few times during the video Ben Underwood is filmed inserting his glass eyes, which may be startling for some students.
Testmybrain.org - Are You a Super Recognizer? Determine if you are exceptionally talented at recognizing faces.
Rippin’ the Rainbow a New One - NPR Radiolab podcast about color perception in humans and other animals. The program answers the question of exactly what dogs can see in terms of color.
Why Food Tastes Different on Planes - BBC article about why airplane food tastes different which is an excellent example of sensory interaction.
The following links are to a two part 60 Minutes episode on face blindness.
World Science Fair Presentation on Face Blindness: Creation of a bell curve in the audience with ten images. Images used, however, include many celebrities many students do not know (e.g. Fred Astaire, John F. Kennedy Jr., Audrey Hepburn).
Faceblind.org – Harvard website which provides detailed information on Prosopagnosia including several tests of face blindness.
Pride and a Daily Marathon –Video about Ian Waterman who suffers from a rare neurological problem that involves a complete loss of his kinesthetic sense.
King of Fruits –Videos related to the Durian fruit, which is considered a delicacy in parts of Southeast Asia but is seen as repulsive by Western tastes. http://video.nationalgeographic.com/video/malaysia_durian
Absolute Threshold, Difference Threshold (JND), Weber’s Law https://www.youtube.com/watch?v=wVhiezByMSU
My Stroke of Insight - TED talk by Jill Bolte Taylor based on her book My Stroke of Insight referenced by the author in the section on neural plasticity.
The Science of Scent – TED talk by biophysicist Luca Turin referenced in the book. He is the subject of Chandler Burr's book The Emperor of Scent. He is currently working on developing an artificial nose.
Video – Oliver Sacks on Face Blindness
Psychological Figures and Concepts
Pierre Paul Broca
Joseph Francis Gall
Sir Francis Galton
Hermann von Helmholtz
Agnosia (Prosopagnosia, Phonagnosia)
Color <ixing (Additive and Subtractive Color Mixing)
CT, fMRI, MRI, PET
Just Noticeable Difference (JND)
Perception (Bottom-Up v. Top-Down)
Photoreceptors (Rods and Cones)
Presbyopia and Presbyosmia