suffers from information withdrawal syndrome
a) Volunteers in the experiment had to spend one day without any electronic device, such as telephones or the internet.
b) Two positive effects have been that...
One positive effect has been that volunteers have improved their facilities for surviving. Another has been that they spent more time outside, walking in the streets, for instance or enjoying nature.
Ex. 4. a) developing / highest b) an / who
c) until / became d) on / spent / used to spend