128 Inside the Living Cell 



continuing process — in fact of something which has been going on 

 since birth. The new sense impressions just take their place as a 

 continuation of a long series and the interpretation which is found 

 in them depends on what has been learnt about the previous 

 experiences. 



This means that the memory record is not a static thing — some- 

 thing finished and done with. It is like a message on a long tape, on 

 which fresh signals are appearing all the time. But there is a vital 

 difference from a tape message. The messages which arrive in the 

 brain are co-ordinated and compared with previous part of the 

 record. We recognize this feature or that feature — in fact the meaning 

 of the sense impression is determined entirely by this comparison 

 with previous experiences and by the interpretations which we are 

 able to make as a result. 



Our experience at any one moment is thus a combination of the 

 sense images of the moment with memories of the past, and it is 

 difficult to separate the one from the other. This characteristic, i.e. 

 that sense impressions are interpreted in terms of the meaning 

 which has been found in previous experiences, seems to be a 

 fundamental ability of the human brain and probably also to a less 

 extent of that of the higher animals. The relative importance of that 

 part coming from the sense and that coming from the memory may 

 vary very greatly. But something of this kind seems to be a necessity 

 where behaviour is to be determined both by the present situation 

 and by what has been learnt from past experiences. 



So far we have been thinking of the impressions reaching the 

 senses in a rather simple way. We have actually tried to isolate rather 

 simple sense impressions and see how they are dealt with. But in 

 practice we are receiving all the time a multitude of sense impres- 

 sions, some important and some unimportant. How do we manage 

 to sort them out? 



It is clear that, out of the multitudinous sense impressions that 

 pour in on us, we are able to produce a consistent picture, which 

 includes the most important elements of the situation which need 

 concern us. This picture necessarily involves discrimination between 

 the important and unimportant; it necessarily concerns itself with 

 the broad outlines and not with every detail of the sense impressions. 

 It is to a great extent built up by recognizing features we are familiar 

 with. Thus one glance at an object is sufficient for us to recognize it 

 as a table. We do not have to study it carefully and try to make up our 

 minds whether it is really a camel or an ant-hill. 



So we see that our sense impressions are not used at first hand; 

 it is the interpretations which we are able to make of them which are 



