Complex sentence: Research suggests that children overgeneralize stress rules when they are reproducing novel Spanish words and that they have a tendency to stress the penultimate syllables of antepenultimately stressed words, to avoid a violation of nonverb stress rules that they have acquired.
Split into simpler sentences: Research suggests that children overgeneralize stress rules when they are reproducing novel Spanish words and that they also have a tendency to stress the penultimate syllables of antepenultimately stressed words. This is to avoid a violation of nonverb stress rules that the children have acquired.