The answer to this question can be found in Chapter II, which is where the tour of how this curious world operates continues, and both the reader and the visitors to the Hatchery see how social conditioning in its most extreme form occurs in this future dystopia. The children who are given electric shocks when they approach books or flowers are selected to be "lower caste workers," and therefore associating books and flowers with pain and loud noises means that they will spend more time working uncomplainingly rather than reading and fomenting revolutionary ideals:

...you couldn't have lower-caste people wasting the Community's time over books... there was always the risk of their reading something which might undesirably decondition one of their reflexes...

It was decided to abolish the love of nature, at any rate among the lower classes...

The children referred to in the book therefore are given shocks whenever they approach flowers or books as a form of extreme social conditioning, so that their future life is shaped for them and they are prepared for the role that this dystopian society has decreed they should have.