Verbal behaviours constitute one of the most important classes of human social behaviour. cultural evolution possible because of communication (talk/listen, read/write) language makes discoveries cumulative, passing knowledge down from generation to generation. The function of language is to induce others to do certain behaviours. Deficit must be relatively isolated (like they can understand what"s going on around them. Agrammatism: a difficulty in comprehending or properly employing grammatical devices, such as verb endings and word order they actually have a tough time comprehending word order as well. Broca"s area is involved in complex grammar and learning grammatical rules. A critical location for speech articulation is the left precentral gyrus of the insula insular cortex is behind the anterior temporal lobe. Tip of the tongue phenomenon or tot: when you want to say a word but can"t think of it occurs a lot in people with loss of gray matter in this region. Still studies indicate broca"s area is involved as well.