HIGHER REACHES ANSWERS: Pork opine: Study finds pigs can be optimists or pessimists, depending on personality and mood [February 14, 2017]

4. the interaction of personality and mood 

5. (i) NG 
(ii) T  
(iii) F

6. The pigs with proactive personalities were optimistic about the chance of finding chocolate in the bowl regardless of the quality of their accomodation. Pigs with reactive personalities, were only optimistic about finding chocolate if they'd stayed in the more comfortable pen.

7. A

8. Like humans, reactive animals are more affected by their environment, and their mood likely affects their choices.

9. B