before. Thus, her 1000 words, or lexicals, should not be regarded as an upper limit, but a benchmark. While there are many components of language that were not demonstrated in this study, the 1000 word benchmark is remarkable because many studies on language learning correlate a 1000 lexical vocabulary with, roughly, 75% spoken language comprehension. Another study on Chaser was published in 2013. In this study, Chaser demonstrated flexible understanding of simple sentences. In these sentences, syntax was altered in various contexts to prove she had not just memorized full phrases or inferred the expectation through gestures from her evaluators. Discovering this skill in a dog is noteworthy on its own, but verb meaning can be fast mapped through syntax. This creates questions about what parts of speech dogs could infer, as previous studies focused on nouns. These findings create further questions about the fast mapping abilities of dogs when viewed in light of a study published in Science in 2016 that proved dogs process lexical and intonational cues separately. That is, they respond to both tone and word meaning. However, excitement about the fast-mapping skills of dogs should be tempered. Research in humans has found fast-mapping abilities and vocabulary size are not correlated in unenriched environments. Research has determined that language exposure alone is not enough to develop vocabulary through fast-mapping. Instead, the learner needs to be an active participant in communications to convert fast-mapping abilities into vocabulary. It is not commonplace to communicate with dogs, nor any non-primate animal, in a productive fashion as they are non-verbal. As such, Chaser's vocabulary and sentence comprehension is attributed to Dr. Pilley's rigorous methodology. In the deaf population A study by Lederberg et al., was performed to determine if deaf and hard of hearing children fast map to learn novel words. In the study, when the novel word was introduced, the word was both spoken and signed. Then the children were asked to identify the referent object and even extend the novel word to identify a similar object. The results of the study indicated that deaf and hard of hearing children do perform fast mapping to learn novel words. However, compared to children with normal hearing (aging toddlers to 5 years old) the deaf and hard of hearing children did not fast map as accurately and successfully. The results showed a slight delay which disappeared as the children were a maximum