Final answer:
The claim that concentrating can control a cold stream causing goosebumps is false. Goosebumps are an involuntary response to cold or fear due to contraction of muscles in the skin, helping in temperature regulation.
Step-by-step explanation:
True or false: when you concentrate, you can control a stream of cold current to flow down the back of your neck, causing goosebumps to appear. This statement is false. Goosebumps occur automatically when you are cold or afraid because of the involuntary contraction of muscles called the arrector pili. These small muscles in the skin pull on hair follicles, causing the hair to stand up and creating the bumps known as goosebumps. This action traps more air under the hairs, which insulates the skin and conserves body heat, contributing to the body's homeostasis. This involuntary response is part of the body's mechanism to regulate temperature and is not something that can be controlled through concentration.