Psychology of Perception
Stephen F. Austin State University
February 19, 1999
Imagine the smell of some freshly baked cookies hot out of theoven, or the clean smell of a brand new car's interior. Have you everthought what it might be like to never smell these scents again? Whatif you could not smell your dinner burning on the stove or the factthat the baby needs a diaper change? The National Institutes ofHealth in 1979 found that around 200,000 people consult their doctorsevery year for the decreased or total loss of smell (Crawford andSounder, 95). The disorder is anosmia, the loss of the sense ofsmell, usually from a sinus infection or a nasal obstruction, whichlasts only temporarily. Anosmia is also known as a permanentcondition commonly resulting from a head injury or disease, such asairopic rhinitis or chronic rhititus associated with granulomatousdisease, which destroys either the olfactory nerve. This smelldisorder can also be caused by psychological factors, such as aspecific fear of a particular smell (Mosby, 94).
Of then five senses, smell seems to be the least appreciated(Gillyatt, 97). Society always gives attention to the senses thatappear most necessary: sight and hearing. Touch and taste appear moreimportant because it is obvious that without them life becomes morechallenging (Gillyatt, 97). Humans are microsmatic, which means thatthe sense of smell is not necessary for survival like with animals(Goldstein, 99). The sense of smell can protect people and thereforeis important. Smell also makes things enjoyable (Gillyatt, 97). Forinstance, when eating a favorite food the taste is much moreflavorful when feeling healthy opposed to being congested. Humans canrecognize as many as 10,000 different scents, compared to the senseof taste , which is limited to four basic categories: sweet, salty,sour, and bitter (Gillyatt, 97). The sense of smell is veryimportant, but taken for granted. Everyone should be aware of anosmiabecause as people age the disorder becomes more and more common.Approximately fifty percent of people over 65 years of age haveexperienced a decrease in smell (Schiffman, 94). It is apparent thatthe weakening of the sense of smell is age related (Cain and Stevens,86). Anosmia is a disorder that needs to be taken seriously. Thepermanent loss of smell can be hazardous to ones health if not dealtwith properly.
Recently, it has been discovered that odors that are sensedsimultaneously are identified individually and consecutively in thebrain, instead of as a mixed odor. Nagel observed that odorcombinations are similar to combinations of color, rather than sound(JAMA, 98). The sense of smell is very complex. Millions of odorreceptors work to identify different scents. The brain sorts thehundreds of signals representing specific odors into round filescalled glomeruli. The glomeruli are a major part of organizing scentperception (Richardson, 95). These glomeruli line the olfactory bulbswhich are connected to olfactory nerves and olfactory tract, theparts of he brain associated with the sense of smell (Mosby, 94).Airflow patterns in the nose allow for scents to reach the olfactoryreceptor cells located on the dorsal side of the nasal cavity,septum, and superior tubinates. These cells are constantly renewing,which takes about one month. People with olfactory dysfunction havedamaged some of their olfactory nerves. Age-related anosmia isusually due to degeneration of the gloneruli and olfactory bulb(Schiffman, 97).
Health can be greatly affected when a person has anosmia. Taste ismost commonly lost with the disorder since there is a closeconnection of smell and flavor (Goldstein, 99). Because anosmiaresults from an olfactory deficit, there is usually a loss of taste.A taste loss is one of the first things noticed by people losingtheir sense smell. This loss of taste can greatly affect a person'seating habits. Many people with anosmia are known to skip mealsbecause the appeal for food is not there. Nothing seems to taste goodanymore and the flavor is gone. Another reason appetite is effected,is that the aroma of foods does not cause a desire for food becausethe person cannot detect the luring odors from the food (Crawford andSounder, 95). Not eating results in malnutrition and involuntaryweight loss. This can also lead to illness because the proper foodsare not being eaten to keep a person healthy. The primary reinforcersfor eating are saticity and pleasure. Without taste and smell theperson will not experience these sensations (Schiffman, 97). Anosmiacan also have the opposite effect and cause a person to overeat tocompensate for the loss of taste. This can result in a weight problem(Crawford and Sounder, 95). Obesity is a major result of elderlywomen with olfactory dysfunction's (Duffy, Backstrand, and Ferris,95).
A study was conducted in 1995 analyzing smell disorders and howthey effect nutrition of elderly women. Eighty women were studied forodor perception and odor identification using the standard olfactorytest from the study by Cain, Gent, Goodspeed, and Leonard. Almosthalf of the women had problematic risks concerning minimal interestin food related activities, minimal preference for foods withsour/bitter tastes, higher intake of sweets and less intake oflow-fat milk products ( Duffy ,Backstrand, and Ferris, 95) Thesolution to these eating disorders is to find ways to make eatingenjoyable again. The texture of food and how they are combined becomevery important to someone with anosmia. Eating a hot meal with a coldsalad allows for different temperature experiences and when eatingvegetables, mixing partially cooked vegetables with fully cooked onesallows for a texture comparison. Another suggestion is to eat spicyfoods that cause sensations on the tongue (Crawford and Souder, 95).The object is to take some time to make meals interesting and fun, sothere is still an appeal to eat and feel satisfied.
The sense of smell is not only important to taste, but it is alsoessential for detecting signs of danger such as smoke, gas leaks andspoiled food. A person living with anosmia needs to take extra safetyprecautions. Smoke detectors are a necessity in all areas of thehome, especially in the kitchen and near fireplaces (Gillyatt, 97).An extra safety is having fire extinguishers in case of a small fire(Crawford and Sounder, 95). Another safety precaution is electricstoves instead of gas stoves. Gas leaks are recognizable by smell andcould not be detected by someone with this disorder (Gillyatt, 97).Household cleaners can be a risk factor because the odor of thechemicals will not be noticed to warn the person that the chemicalsare toxic and should be used in a well- ventilated area. Warninglabels should be read as a reminder of the chemicals involved in suchthings as hair products, bathroom and kitchen cleaners, insecticides,etc. Our sense of smell keeps people aware of automotive troubles.Regular checkups should occur to prevent problems. The sense of smellis also very important in detecting spoiled food. To prevent thisleftovers need to be marked with throwaway dates and specialattention needs to be given for freshness dates to be sure the foodis good and safe to eat (Crawford and Sounder, 95).
Some people are more likely to have olfactory deficits. People,ages 65 and over, commonly experience progressive impairment in bothtaste and smell. The proportion and population of the elderly isconstantly increasing and they are experiencing age related sensoryloss. The most publicized sensory loss of the elderly has been sightand hearing. There has not been much attention or research doneregarding the loss of smell. The main cause of olfactory loss isnormal aging. Diseases, medications, surgical intervention andenvironmental exposure can also be related. One study found arelation with seizures and smell disorders. Patients who had sufferedfrom two types of seizures, mesial temporal lobe and neocortical,were studied to see if testing olfactory functions is useful todistinguish between the two seizures. The results found that mesialtemporal lobe seizures impaired olfactory quality discrimination andresulted in lower delayed recognition scores than neocorticalseizures (Savic, 97). These results imply that the seizures affectdifferent parts of the brain, and that the many different aspects ofare sense of smell can be impaired without complete damage.
Anosmia with the elderly can be a real problem. Many elderlypeople live in nursing homes. This is a situation where a person withanosmia may tire of the food because it is bland to them. Eatingbecomes boring and can cause a person to not eat, which can lead toweight loss. Younger individuals are able to distinguish the degreesof difference between odors of different quality much better than anelderly person is. The difficulty of identifying odors becomes verycommon once over the age of 80 (Schiffman, 94). One study thatsupports the age-related olfactory loss also found that both men andwomen's sense of smell decrease with old age, but women didsignificantly better than the men when using Pennsylvania's SmellIdentification Test (Brant, Cruise, Metter, Pearson, and Ship, 96).The topic of anosmia is growing. More and more people have becomeaware of this disorder in the past few years. Today's sense of smellis mostly for practical purposes when compared to the early stages ofthe evolution (JAMA, 98) but, it should not be taken for granted.Medical research will hopefully discover ways to rehabilitate thesense of smell when it is lost so meals can always be enjoyed,healthy living practical, and everyone can live safer.
Crawford, D. C, Sounder, E., (1995). Smell disorders = danger. RN,58 (11), 40-44.
Duffy, V. B., Backstrand, J. R., Ferris, A. M., (1995). Olfactorydysfunction and related nutritional risk in free-living elderlywomen. Journal of American Dietetic Association, 95 (8), 879-885.
Mosby (1994). Mosby's Medical, Nursing and Allied HealthDictionary. Mosby-Yearbook Inc.
Gillyatt, P., (1997). Loss of smell: when the nose doesn't know.Harvard Health Letter, 22, 6-8.
Goldstein, E. B. (1999). The Chemical Senses. Sensation andPerception. M. Taflinger (5th Ed.). Pacific Grove, CA. Brooks/ColePublishing Company.
JAMA, (1998). The psychologic psychology of smelling. The Journalof the American Medical Association, 279 (1), 16G.
Richardson, S., (1995, August). The smell fires. Discover, pp.30-32.
Savic, I., (1997). Olfactory bedside test: a simple approach toidentifying temporo-orbitofrontal dysfunction. The Journal ofAmerican Medical Association, 278 (6), 464E.
Schiffman, S. S., (1997). Taste and smell losses in normal agingand disease. The Journal of the American Medical Association, 278(16), 1375-1381.
Ship, J. A., Pearson, J. D., Cruise, L. J., Metter, E. J., (1996).Longitudinal changes in smell identification. The Journals ofGerontology, Series A., 51 (2), M86-92.
Stevens, J. C., Cain, W. S., 1986). Smelling via the mouth: Effectof aging. Perception and Psychoanalysis, 40 (3), 142-146.