▶ Your Answer :
In the lecture, the speaker contends that the theories suggested in the reading passage are groundless. Therefore, she casts doubt on the reading passage's point that brain size has gradually decreased for several reasons.
To start with, the lecturer asserts that it is unlikely that more convenient and large human societies have caused an decrease in brain size. She points out that these days, complex mental processes require people to use their brain. For example, nowadays, people have to interact with diverse people so they need to develop social skills. This is in direct opposition to the reading's argument that the decline in brain size has been caused by more comfortable and large human societies.
On top of that, the speaker argues that the a decline in human body size cannot contribute to the drop in brain size. To be specific, many experts show that the human body has shrunk at a faster rate than the brain did. If the decrease in human body size had been a important reason for the reduction in brain mass, the brain would have been shrunk at a similar rate. This is contradictory to the reading passage's assertion that the decrease in human body size has led the brain to shrink.
Lastly, the speaker maintains it is unreasonable that the visual cortex, the part of the brain responsible for making visual data, has resulted in the drop in brain mass. She supports her idea by saying that this part consists of a very small part of the brain. Therefore, this cannot cause a formidable change in brain size even though the visual cortex has significantly shrunk. This rebuffs the reading's insistence that the visual cortex is the reason for the reduction in the brain mass.
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