Is Learning Always Observable?

I believe learning is observable, especially in more social, extroverted students. However, as previously discussed, it is harder to observe whether learning has happened in more introverted students who are less likely to express their thoughts, ideas, questions, etc. With that being said, I also believe people can be both intro- and extroverted in different situations depending on their "comfort zone." 
Now to determine whether or not a student has learned, we can observe the types of questions students are asking. If they are asking thought-provoking questions, it shows they have thought a little about the topic or are in the process of learning. If children participate in discussions freely and openly, that is also an indication learning as happened. Most of the time, I think, if students are engaged in class discussions, show an interest, and can relate the material to their own experiences and stories, they are learning. Testing material in the form of a unit exam or something similar can be a method of evaluation, however, memorization does not always indicate the student has actually learned the material. 
While the above methods of observation/evaluation is great for students who are comfortable voicing their thoughts and opinions, there are some students in the classroom who do not feel at ease when having to talk. So, with those students in mind, learning can also be observed through reflective journals where they have time to write their thoughts down, ask questions and even answer those questions. Learning can also be observed through one-on-one conversations with the student.
Lastly, I believe learning can best be observed by giving individual students most of the control over their own learning. For example, students may design their own projects with teacher approval/support, so that whatever they choose to do, they are able to display exactly what they have learned in a manner in which they are comfortable. 
- Rita Shahi