CHAPTER XX 



The sense of taste 



CARL PFAFFMANN [ Psychology Department, Brown University, Providence, Rhode Island 



CHAPTER CONTENTS 



Receptor Anatomy 

 Neuroanatomy 

 Receptor Mechanisms 



Functional Characteristics 

 Sensitivity and Mechanisms of Stimulation 

 Sour 

 Salty 

 Sweet 

 Bitter 



Electric taste 

 Parameters of Stimulation 

 Temperature 

 Area and duration 

 Reaction time 

 Adaptation 

 Intcnsitivc Relations 

 Behavioral Effects 



THE SENSE OF TASTE, as distinct from the other chemo- 

 ceptors, olfaction and the so-called common chem- 

 ical sense, is associated with specialized receptor 

 organs, the taste buds, which in land-inhabiting ver- 

 tebrates are located in the mouth. In aquatic animals 

 and insects chemoreceptors may be distributed o\er 

 the body surface or on special appendages (68, 152, 

 197). In man taste stimulation is associated with the 

 sensation qualities of salty, sour, bitter and sweet. 



Of the three chemoceptors, common chemical 

 sensitivity is the least differentiated and rcc|uires 

 relatively high concentrations for stimulation. Indeed, 

 the distinction between chemical sensitivity of the 

 mucous membranes or moist skin surfaces and general 

 pain sensitivity has been questioned (60, 112, 161). 

 Some chemical irritants may be classed as lachryma- 

 tories or suffocants (144), depending upon their sites 

 of action, but this may be a differentiation largely 

 because of the surrounding structures. A familiar 



dissociation of taste and smell often occurs in the 

 temporary anosmia during the common head cold. 

 Under normal circuinstances, exclusive stimulation 

 of taste can be insured by placing dilute odorless 

 solutions on regions of the tongue possessing taste 

 buds. But many stimuli will activate all three senses 

 with varying degrees of overlap. 



The chemical senses are often classed among the 

 lower sen.ses (198) perhaps because of simplicity of 

 morphology, relative paucity of information con- 

 veyed and relative unimportance in the sensory life 

 of man. Indeed, the loss of taste is hardly as incapaci- 

 tating as the loss of vision or hearing, at least to civ- 

 ilized man. At the same time, the chemical senses 

 mediate such adaptive functions as food selection or 

 the rejection of noxious stimuli, particularly in the 

 case of lower organisms where dramatic examples 

 may be cited (104, 177). 



RECEPTOR AN.^TO^n• 



The taste buds in man and other mammals are 

 located primarily on the edges and dorsum of the 

 tongue, and adjacent .surfaces of the upper margin 

 of the gullet, epiglottis, soft palate and pharynx (124, 

 150, 198). On the tongue, taste buds lie in the upper 

 surface of the mushroom-shaped fungiform papillae, 

 in the grooves of the foliate papillae, which are a set 

 of three to eight folds at the side of the tongue near 

 the base and in the circular trench of the vallate 

 papillae which form a chevron-like row of from 6 to 

 15 papillae on the dorsal surface of the base of the 

 tongue (see fig. i). The slender keratinized filiform 

 papillae over most of the dorsuin contain no taste 

 receptors. In certain animals like the rodents, taste 

 buds occur on the anterior hard palate, especially in 

 and around the nasoincisor ducts (i 15). 



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