330 BEHAVIOR OF THE LOWER ORGANISMS 



of sand, and in general all lower organisms show discrimination in many 

 phases of their behavior. 



Choice is a term based objectively on the fact that the organism ac- 

 cepts or reacts positively to some things, while it rejects or reacts nega- 

 tively or not at all to others. In this sense all lower organisms show 

 choice, and at this we need not be surprised, for inorganic substances 

 show a similar selectiveness. The distinctive thing about the choice of 

 organisms is that it is regulatory ; organisms on the whole choose those 

 things which aid their normal life processes and reject those that do not. 

 This is what justifies the use of the term "choice," as contrasted with 

 the mere selectiveness of inorganic reactions. Choice in this regulatory 

 sense is shown by lower organisms, as we have seen in detail in previous 

 chapters. Choice is not perfect, from this point of view, in either lower 

 or higher organisms. Paramecium at times accepts things that are use- 

 less or harmful to it, but perhaps on the whole less often than does man. 



The methods by which choice is shown in particular organisms have 

 been set forth in our descriptive chapters. We may refer particularly 

 to the account of choice in the infusoria, given on page 183. The free- 

 swimming infusoria as they move about are continually rejecting cer- 

 tain things and accepting others, and this choice is regulatory. Their 

 behavior is based throughout on the method of trial, and this 

 involves an act comparable to choice in almost every detail. Whatever 

 the condition met, the infusorian must either accept it by going ahead, 

 or reject it by backing and giving the avoiding reaction. We can al- 

 most say that its whole behavior is a process of choice; that choice is 

 the essential feature of its behavior. For the other lower organisms 

 that we have taken up, a consideration of details would discover 

 activities involving regulatory choice almost as continuously as in the 

 infusoria. 



Is not what we call attention in higher organisms, when considered 

 objectively, the same phenomenon that we have called the interference 

 of one stimulus with the reaction to another ? At the basis of attention 

 lies objectively the phenomenon that the organism may react to only one 

 stimulus even though other stimuli are present which would, if acting 

 alone, likewise produce a response. The organism is then said to at- 

 tend to the particular stimulus to which it responds. This fundamental 

 phenomenon is clearly present in unicellular organisms. Stentor and 

 Paramecium when reacting to contact with a solid "pay no attention" 

 to a degree of heat or a chemical or an electric current that would pro- 

 duce an immediate reaction in a free individual. On the other hand, 

 individuals reacting to heat or a chemical may not respond to contact 

 with a mass of bacteria, to which they would under other conditions 



