In pavlov's experiments on classical conditioning, prior to associating the sound of the bell with the food, the dog's salivation in response to the food was the

They were conditioned to salivate in response to the sound of a bell.

measuring light intensity

light meters can be used to measure light intensity. the meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

errors can be made when measuring light intensity by accidentally shading the light meter. the reliability of the results can be checked by taking many samples.