A researcher conditions rats to associate a light stimulus with a wavelength of 530 nm530\text{ nm}530 nm (the conditioned stimulus) with the presentation of a sugar solution. After training, the rats salivate when they see the 530 nm530\text{ nm}530 nm light, even in the absence of the sugar solution. The researcher then tests the rats' response to four other light wavelengths: Wavelength A (420 nm420\text{ nm}420 nm), Wavelength B (510 nm510\text{ nm}510 nm), Wavelength C (550 nm550\text{ nm}550 nm), and Wavelength D (640 nm640\text{ nm}640 nm).
Explain how a simple reflex response, such as salivation, differs from a voluntary response, such as pressing a lever.
Identify the sense organ and the specific type of receptor cell the rats use to detect the light stimulus.
The researcher observes that Wavelength B and Wavelength C produce a significantly greater salivation response in the rats than Wavelength A and Wavelength D. Suggest a reason for this observation.
Suggest two ways the researcher could measure the quantity of the saliva produced.
