According to Scout Jem does not like to turn down a dare, but he is afraid to approach the Radley home. However, after Dill modifies the challenge to just touching the house instead of trying to get Boo to come outside, Jem accepts. So, he touches the Radley house in order to not be accused of lacking courage and because doing so is not as frightening as the first proposal.
In Chapter 1 Scout and Jem meet Charles Baker Harris, alias Dill, who demonstrates quite an imaginative personality. Having heard about the mysterious Boo Radley, Dill feels that they need to flush him out. "Wonder what he looks like?" Dill asks. When he asks this question, Jem warns Dill that Boo Radley could come outside and "kill each and every one of us." But, Dill's retort is that Jem is afraid, moreover, Jem confirms that he is fearful by saying that he has a sister to protect. Scout provides evidence that Jem is afraid because once when she dared him to jump off the house, he made the excuse that if he died, she would have no one to look after her.
Finally, Dill challenges Jem: "You gonna run out on a dare?" Jem tries to reason with Dill; finally, Dill reduces his challenge to just touching the house, and he tells Jem that he won't say that Jem ran out on a dare. Jem definitely does not want to be accused of running out on a dare.
Jem brightened. "Touch the house? That's all?"
Jem speeds to the other house and runs back, panting.