When adults move their eyes across a line of text, adult readers focus - it s called the fixation. Our eye span is typically two to three letters to the left and fifteen letters to the right of where we fixate. So we can see quite a bit. If space between words is too small, they keep having to search for where the next word starts. There is also the psycholinguistic element of reading.
Children respond to repetition almost innately, and they respond to rhythm and rhyme naturally.
They have inferred enough about the English language that they have a sense of how it flows. So if the text matches their sense of the language, it helps. For instance, Todd said, I want to play. Beginning readers stop after I want to play, so said Todd seems to run into the next sentence, but young readers know we don t start a new sentence with said Todd. The way the text is laid out, and how it flows with the rhythm, rhyme, repetition and matches children s knowledge of how language is organized are important.