The common claim that compounds are fossils of language often complements the argument that they contain a flat, linear structure. However, Di Sciullo provided experimental evidence to dispute this. With the knowledge that there is asymmetry in the internal structure of exocentric compounds, she uses the experimental results to show that hierarchical complexity effects are observed from processing of NV compounds in English. In her experiment, sentences containing object-verb compounds and sentences containing adjunct-verb compounds were presented to English speakers, who then assessed the acceptability of these sentences. Di Sciullo has noted that previous works have determined adjunct-verb compounds to have more complex structure than object-verb compounds because adjunct-verb compounds require merge to occur several times. In her experiment, there were 10 English speaking participants who evaluated 60 English sentences. The results revealed that the adjunct-verb compounds had a lower acceptability rate than the object-verb compounds had a higher acceptability rate. In other words, the sentences containing the adjunct-verb compounds were viewed as more "ill-formed" than the sentences containing the object-verb compounds. The findings demonstrated that the human brain is sensitive to the internal structures that these compounds contain. Since adjunct-verb compounds contain complex hierarchical structures from the recursive application of Merge, these words are more difficult to decipher and analyze than the object-verb compounds which encompass simpler hierarchical structures. This is evidence that compounds could not have been fossils of a protolanguage without syntax due to their complex internal hierarchical structures.