Is learning observable?

I feel that it is important to ask students what they learned at the end of each day.  This can be done in journal format, by drawing a picture, speaking into a recording device, or simply having a conversation with the teacher or another student.  It is beneficial for students to look back on their day and jot down a few thoughts about what happened in regards to the curriculum taught, their peers, and themselves.  Having said this, I do believe that learning is observable to a point.  Teachers need to pay attention to what their students are doing by noticing body language and student interactions.  I feel it is important to keep introverts and extroverts in mind when asking this question.  As many of my fellow classmates have already mentioned, a student can possess introverted qualities in the classroom and yet be an extrovert on the playground.  In saying this, it is the teachers responsibility to provide as many options possible for students to be able to express themselves and what they have learned by creating lesson plans that reach all types of learners.  Testing is not always the answer.  However, there is a time and place for everything.  Learning may not always be observable but I do believe that learning mostly occurs in the students who want to learn.