Concept:
Learning is considered an internal psychological process. It cannot be seen directly, but its effects can be observed through changes in behaviour, performance, skills, or attitudes.
Since learning occurs internally in the mind, it is inferred from observable behaviour rather than observed directly.
Step 1: Examine Assertion (A).
The statement:
\[
\text{``Learning is not directly observable''}
\]
is correct because learning is a mental and internal process.
Step 2: Examine Reason (R).
The reason states that learning is an internal phenomenon and behavioural change cannot be directly observed as learning itself.
This statement is also correct.
Step 3: Check whether the reason explains the assertion.
The reason correctly explains why learning is not directly observable.
Hence:
\[
\boxed{\text{Both (A) and (R) are correct and (R) is the correct explanation of (A)}}
\]
Therefore, the correct answer is:
\[
\boxed{(A)}
\]