This was actually covered in a drawing book I recently. For one thing, the shadow areas you mention are pretty much defined as the darkest areas, either on the form or the shadow cast by the form. So technically: no. However, a shadow area is sometimes perceived as darker than it really is when bordered by a lighter area. The same can occur with lights, where an area can appear lighter than it is when bordered by a much darker value. I'm not totally sure if this answers your question. Sometimes the shadow cast by an object and the form shadow on the object can merge or appear to merge, depending on the position and brightness of the light source. This may or may not be what you're thinking.
well, I'm not quite sure what you mean. You will obviously have the gradation leading into the form shadow, which is the darkest area on the form. And there is going to be a slight gradation as you move out of the cast shadow.
Do you maybe have an example of what specifically is concerning you?
not exactly, I saw a drawing that had alot of variation inside of a shadow between lights and darks but didn't know if it was abstract work or if the artist was putting something from real life in that I didn't know about lol Never been to art school, your gonna have to be patient with me haha
It might be more specific to say proximity of light source, i.e. a light shined closer to the object will create greater contrast than the light positioned farther away.