B.F. Skinner, the father of Behaviorism (CBT) and those following him adopted a specialized brain model. Areas of the brain are associated to performing tasks, seeing, smelling, language, etc. Each of these tasks is mapped out to see what parts of the brain are involved. Skinner and reductionist brain models make predictions based on manipulating stimuli in a specific region to discover how abnormalities generate. They have a hypothesis, such as Broca’s Area is responsible for speech. Broca’s Area is involved in lips, breath, vocal cords, larynx, word retrieval, and how it is linked to memory. Humans have a Broca’s Area, other mammals do not. Birds are the closest, they have a similar singing area.
Therefore, it is safe to hypothesize that Broca’s Area is necessary for speech. This falls apart quickly when you change the definition of speech to exclude vocalization. The develop in Children with hearing impairment and loss uses the verbalization function of Broca’s Area when signing. https://www.sciencedirect.com/topics/psychology/brocas-area Verbalization is switched for signing. The Deaf person speaking with you is asking a small area of the brain to perform double duty, sign and speak. Your typical brain wonders why their speech is different and begins making up reasons. The reason is simple, running two complex functions out of one outlet leads to complications. Save everyone trouble and ask the Deaf person how they would prefer to communicate with you.
How does your dog understand “sit”, “stay”, or “out of the garbage!”? Tone for sure. Does your dog comprehend those words? How does your dog feel when you talk to it? Are dogs better empaths, sniffers, and body readers than humans that they can understand you without the ability to communicate back? Does your dog communicate with you? Impossible for the dog to comprehend language they have no Broca’s Area, and nor do apes.
Koko was an ape who learned to speak without verbalization. Koko boasted a vocabulary of over 1,000 words. From Time Magazine,
Most remarkably — and most poignantly — were the thoughts and sentences Koko built. “You key there me cookie,” she signed to Patterson, instructing her to unlock a cabinet and bring a treat. It was impressive enough for the clarity of its meaning, but there is also the use of the imperative “you,” silent and implied in human sentences, expressed in Koko’s. And there is the “there,” the designation of a point in three-dimensional space. https://time.com/5318710/koko-gorilla-life/
Without a Broca’s Area how did Koko speak? If you figure it out let me know.