SUMMARY 



of a paper on THE EFFECT OF SOME ANTECEDENT DETERMINANTS 



ON THE EMOTIONALITY OF THE RAT AS MEASURED BY THE 



OPEN-FIELD TEST read fo the Psychology Section ot the IU6S at 



Brussels, August 1957 by P. L. BROADHURST 



(INSTITUTE OF PSYCHIATRY ; UNIVERSITY OF LONDON) 



Hall's open-field lest of ■emotionality in the rat has been extensively 

 used in our Animal Psychology Laboratory in a standardized version which 

 was developed from a study of physical stimuli (e.g., noise and light) which 

 elicit the defecation and ambulation responses observed in this test. It 

 is this standardized form of the test which has been used in turn for study- 

 ing the effects of external influences on the rats' scores, such as their life 

 history and their inherited characteristics. Among such factors, the 

 following had no significant effect in our experiments on defecation 

 scores: 



(a) deprivation of form vision from birth until the standard age of 

 testing (100 days), 



(6) handling or gentling daily from 56 days of age until tested, and 



(c) sexual experience, including parturition and suckling a litter in 



females, before testing. 



The ambulation scores were, however, significantly increased by 

 sexual experience. This effect was observed in both sexes, and is atlri- 

 buable in females to the experience of suckling a litter. Defecation was 

 reduced significantly by : 



(e) previous experience of the same test at an early age, though this 

 effect is confined to young rats (50 days old) and is not seen in older ones. 



Both the defecation and the ambulation scores were affected by : 



(/) strain differences, as was seen in a study of five pure-bred strains 

 of different coat colours, which, together with a selective breeding study 

 of emotionality now at the seventh generation, provides a basis for a gene- 

 tical analysis of this behavioural trait in the rat. 



