While both William Golding and Mary Shelley have created hypothetical situations in order to examine the nature of human beings, their approaches and motivations for doing so differ greatly. Yet, at the same time, they do share an examination of how environment affects humans and what is the intrinsic nature of these beings.
Affect of environment
Certainly the affect of environment upon a person's character is one that is examined in both novels. Whereas the deprivation of human society and its nurturing and love is responsible for the evil that the creature does in Frankenstein, in Lord of the Flies it is the the deprivation of society that allows the inherent evil of the boys' nature emerge. For Shelley, then, it is the lack of society which causes evil, but for Golding, it is the lack of society which allows the evil nature of man--the beast--to emerge.
Golding's depiction of humanity is that it is inherently flawed by evil. In Chapter Six of Lord of the Flies, for instance, he writes,
However Simon thought of the beast, there rose before his inward sight the picture of a human at once heroic and sick.
On the other hand, the creature is sympathetic to the Delaceys as he vicariously participates in their lives. It is not until he is rejected by them and others just as he has been rejected by Victor, that the creature seeks vengeance and "[E]vil thenceforth became my good," as he says.
Nevertheless, both the boys of Golding's narrative and the creature of Shelley's work become obsessed with their evil activities. As he talks with Walton, the creature remarks,
"The completion of my demoniacal design became an insatiable passion."
Certainly, the same words can be uttered by Jack or by the sadistic Roger of Lord of the Flies who, having toyed with the littl'uns and tormented Ralph in their climb up the mountain to see "the beast," acts in Chapter Eleven, "with a sense of delirious abandonment, leaned all his weight on the lever" that vaults the granite boulder onto poor Piggy's head, sending him to his death.
The intrinsic nature of man
In their narratives both Shelley and Golding examine the inherent nature of man. As a response to the novel The Coral Island in which Victorian English boys defeat the savages on the island where they are stranded, the boys of Golding's novel display fewer and fewer noble qualities during the progression of the narrative. Without the restraints of society, Jack and the others become virtual savages. However, in Shelley's novel, the creature is much like the "noble savage" of the Romantics as expressed by Jean-Jacques Rousseau; it is only when society interferes with him by rejecting him that the creature becomes corrupted and turns to his evil acts of revenge for the wrongs done to him.
Thus, there are, indeed, parallels between Golding's and Shelley's works in their examination of the affect of environment and the inherent nature of man. However, the conclusions to which each author leads the readers are different.