A researcher conditions domestic dogs to associate a flashing blue light of frequency 8 Hz8\text{ Hz}8 Hz (the conditioned stimulus) with the presentation of meat powder. After training, the dogs salivate when they see the 8 Hz8\text{ Hz}8 Hz flashing light, even in the absence of food.
The researcher then tests the dogs' response to four other flashing light frequencies:
Explain how a simple reflex response, such as salivation, differs from a voluntary response, such as walking towards a feeding bowl.
Identify the sense organ and the specific type of receptor cell the dogs use to detect the light stimulus.
The researcher observes that Frequency B and Frequency C produce a significantly greater salivation response in the dogs than Frequency A and Frequency D. Suggest a reason for this observation.
Suggest two ways the researcher could measure the quantity of the saliva produced.
