Final answer:
The part of the brain that increases in activity when parents hear their child cry is the Amygdala, which is primarily involved in processing emotions and emotional memories.
Step-by-step explanation:
When parents hear their child cry, the part of the brain that increases in activity is called the Amygdala. The amygdala is known to play a crucial role in processing emotions such as fear, anxiety, and emotional memories. It is composed of various subnuclei, including the basolateral complex, which is essential for classical conditioning and attaching emotional value to learning processes and memory, and the central nucleus, which is involved in attention and regulating the autonomic nervous and endocrine systems.
The amygdala is a part of the limbic lobe in the medial region of the temporal lobe and makes strong connections with the hypothalamus. This allows it to influence a wide range of emotional reactions. When a parent hears their crying child, it is the amygdala that becomes particularly active as it assesses the emotional significance of the sounds and triggers an appropriate response.