Roger is an interesting study because he is constrained primarily by fear of punishment for breaking the rules. Once that fear goes away, such as happens on the island, Roger has no inward mechanism to keep him from sadism.

Golding very carefully sets up the way Roger tests the new boundaries and starts to work out what he can get away with. We learn that Henry is the smallest of the little boys, making him the easiest to pick on. While at first Roger contents himself with kicking apart the castles in the sand the little boys have made, he waits to throw the stones at Henry. Roger only begins to do this when Henry has wandered off to play by himself. Roger also carefully looks around to make sure that older boys like Piggy and Ralph are far away and busy. At this point, he begins to throw the stones at Henry cautiously:

Yet there was a space round Henry, perhaps six yards in diameter, into which he dare not throw.

Ralph knows from past experience that someone in authority might punish him for throwing stones at another boy. Therefore, at this point, he restrains his aggressive impulses: the rules of civilization still operate for him

In this chapter, however, Roger begins, tentatively, to shed civilized norms. He chooses Henry because the boy is small, weak, and can't easily fight back. He is a safe subject on which to experiment. A boy like Roger will quickly revert to savagery once he realizes that he can, but at this point, he does not feel free to do so.

In chapter 4, Roger throws stones at Henry from distance but aims to miss because he has been conditioned by society not to harm others. At this point in the story, the boys have not spent a significant time on the island and are still heavily influenced by their previous lives. As former British schoolboys, Roger and the others are used to obeying rules and behaving civilly. Although Roger is a sadist at heart and will eventually transform into a cruel savage, his previous experiences have conditioned him not to hit other people with stones.

When Roger sees Henry distracted and playing in the sand, he takes the opportunity to entertain himself by throwing stones in his direction. Roger is experimenting with his newfound freedom and unconsciously getting in touch with his primitive instincts. In Roger's former life, he would have certainly been punished for hitting Henry with stones and understands that doing so would be considered taboo. Even though there are no adults or authority figures to punish him for hitting Henry, Roger is predisposed to avoid the consequences typically attached to this deviant behavior. However, the longer the boys spend on the island, the more they embrace their primitive instincts and savage nature. Eventually, Roger quits Ralph's group to join Jack's tribe and develops into a hostile sadist, who enjoys torturing and killing others.

In chapter 4, Roger watches from a distance as several littluns play on the beach. Roger then picks up a handful of stones and begins to throw them at Henry, who continues to play in the sand. Roger throws stones at Henry because it amuses him and because he is experimenting with breaking the rules that he grew up obeying. Interestingly, Roger is careful not to hit Henry and purposefully aims approximately six yards away from him. Golding writes,

"Here, invisible yet strong, was the taboo of the old life. Round the squatting child was the protection of parents and school and policemen and the law. Roger’s arm was conditioned by a civilization that knew nothing of him and was in ruins" (87).

Essentially, Roger is still influenced by society's laws and expectations, which is why he is careful not to hit Henry with any of the stones. Roger has not been on the uninhabited island long enough to disregard the rules and customs of his childhood, which he learned growing up in Great Britain. At home, Roger would have been punished for hitting Henry with stones and avoided breaking the rules. Roger's intentionally poor aim illustrates the extent of his conditioned behavior. As the novel progresses, Roger gradually descends into savagery and completely disregards his learned civil behaviors.

Chapter four is an interesting chapter in that it represents the boys losing their sense of what it means to be civilized. Roger is losing the restraints that society demands which allows him to throw the rocks, however he is still the tied to the traditions and restraints that is required by a civilized society. It is the latter that prevents Roger from actually hitting Henry. Golding  suggests that there is a moment for all human beings when they have the capability of possessing both of these powerful conflicting emotions. Once the 'rules' are ignored, whatever those rules are, most of humanity will have trouble being 'human'.

Roger's throwing rocks at Henry seems merely like a boyish game at first. He is, after all, "throwing to miss" the child. The narrator tells us that Roger does not hit Henry because around him there circled a "taboo of the old life"--a life full of "parents and school and policemen and the law." These things have always kept Roger and the other boys in line. Roger, whose arm is "conditioned by a civilization that knew nothing of him and was in ruins," will not respect these taboos for much longer. He will become one of the most brutal members of Jack's tribe.