1508 



II WllllllIlK OK PHYSIOLOGY 



NEUROPHYSIOLOGY III 



havioral terms and how we may measure motivation 

 experimentally. 



!'.!■ HAVIORAL DEFINITION OF MOTIVATION 



In order to approach this difficult task of analysis 

 and definition of motivated behavior, it will he help- 

 ful to start with two simple examples of motivation. 

 This first is an instance cited by Lashley (Hfi) of the 

 motivation to ingest Hydra seen in the round worm, 

 Microstoma. This worm uses stinging cells to capture 

 prey and in its defense, but it must acquire these cells 

 from Hydra. When Microstoma has lost its stinging cells, 

 it ingests Hxdra voraciously. As stinging cells are 

 accumulated, they are evenly distributed around the 

 surface of the body, and triggering mechanisms are 

 grown out to them. A point is reached, however, 

 when Microstoma has a full complement of stinging 

 cells and it no longer ingests Hydra, even in the com- 

 plete absence of all food sources. 



Illustrated here are a number of basic concepts of 

 motivation. The first is the concept of 'physiological 

 need,' represented in this case by a lack of stinging 

 cells. Second is 'drive 1 shown by the increased activity 

 of Microstoma in the face of its deficit. Third, there is 

 'goal' and 'goal-directed activity' represented, re- 

 spectively, by Hydra and by the specific selective ac- 

 tivitv M/tttntoma shows in the approach to and inges- 

 tion of Hydra. Fourth, is "satiation' shown by the 

 failure of Hydra to elicit further specific goal-directed 

 activity, and the reduction of general activity in 

 Microstoma, or its quiescence, once it has corrected its 

 defii it of stinging cells. 



I he same concepts derive from a second example, 

 a case of s.ih hunger in a three-year-old child unable 

 to retain -..h because adrenal tumors caused an in- 

 sufficiency of adrenal cortical hormones (169). Here 

 the physiological need is the salt deficit; this child was 

 restless and agitated, especially during feeding, in- 

 dicating an undirected drive. The goal of salt became 

 apparent in the child's marked preference for bacon 

 and sod. i crackers from which he licked the salt. I he 

 goal-directed behavior became eve ire obvious 



when the child accidentally discovered the salt shaker 

 ind ate sail by the teaspoonful. He then learned to 

 ask for salt in his prelanguage years by si reaming and 

 nting to the cupboard where -ah was kept; it is 

 perhaps significant, moreover, thai his firs! word was 

 'salt.' hollow iny bonis of salt ingestion, the child 

 showed satiation; he was no longer interested in the 

 -.ill shaker, he no longer preferred salt) foods, and hi- 



general appetite improved. Of course, as salt was lost 

 from the body, the need returned and the whole cycle 

 repeated itself. In this way the boy managed to keep 

 himself alive until he was brought to a hospital for 

 observation and unfortunately was placed on a normal 

 salt diet which kept him alive for only 7 days. 



These two examples are particularly interesting 

 because they show how the same kind of behavioral 

 analysis applies over a wide range of the phvlogenetic 

 scale, up to and including man. Furthermore, in con- 

 trast to the first, the second example illustrates quite 

 clearly the role of learning in the organization of 

 motivated behavior, particularly in the selection of 

 goals and in the use of specific responses, among them 

 language, as instrumentalities in the development of 

 goal-directed behavior. 



Not all instances of motivated behavior fit this 

 pattern completely nor is it a simple matter to go from 

 this behavioral analysis to experimental investigation 

 of underlying physiological mechanisms. But it is 

 possible to make some headway in this direction and, 

 at the same time, to evaluate these behavioral con- 

 cepts in the light of physiological data and theories. 



Need 



The concept of physiological need was a valuable 

 one in the past, for it gave the study of motivation 

 biological roots. Classically, it has been specified as 

 some physiological deficit or imbalance in the in- 

 ternal environment that, in the extreme at least, would 

 endanger the life of the organism 03°)- Unfortu- 

 nately, however, the term has been badly abused and 

 overworked. First of all, need has lost some of its bio- 

 logical significance for it has been inferred by some 

 workers in almost every kind of motivation, without 

 any physiological reference (111). Moreover, as we 

 have already pointed out, not all physiological needs 

 lead to motivation and not all motivation derives 

 from needs or deficits. From a physiological point of 

 view, furthermore, specification of an internal en- 

 vironment factor in the control of motivation is far 

 more inclusive than a concept of need. And finally, as 

 you will see in a moment, the concept of drive can 



easily be substituted for need at the behavioral level. 

 Thus, il appears that the historical concept of need is 

 superfluous, and perhaps misleading, in the analysis 

 of motivation and should be dropped from use. 



Drivt 



Drive is a purely behavioral concept 1l1.1t refers to 

 the inteiisiiv of motivated behavior, regardless of how 



