Please, correct my essay.

The reading passage stated that it has been shown that your brain reacts to pain the same way it does if your brain thinks it will receive pain. The lecturer stated that a group of scientists worked with 10 volunteers that wore a device on their right leg. This device created three levels of heat from mild, medium to strong. The time between each exposure to heat would be longer for the hotter levels. After that, scientists started to change the time and amount of heat. Although the delay was 30 seconds and heat was mild, the volunteers still claimed that the level of pain was strong