<p>Jean Piaget, a Swiss psychologist, and the first scientist that made systematic studies of how children learn.</p>
<pre><code>* (A) Jean Piaget, a Swiss psychologist, and the first scientist that made
* (B) Jean Piaget was a Swiss psychologist, also the first scientist making
* (C) As a Swiss psychologist, it was Jean Piaget who was the first scientist making
* (D) Swiss psychologist Jean Piaget, the first scientist in having made
* (E) The Swiss psychologist Jean Piaget was the first scientist to make
</code></pre>
<p>I picked (E) only because the other choices seemed more incorrect. If we think in the lines of choice-(E) shouldn't it go more like- The Swiss psychologist, Jean Piaget, was the first scientist to make ... ? Isn't "Jean Piaget" a parenthetical phrase?</p>
<p>Because there is more than one Swiss psychologist, we do not use commas (restrictive apposition).</p>
<p>Just looked up “restrictive apposition.” Thanks.</p>
<p>You can also think of it in this way (if you hadn’t already): Commas introduce modifying phrases. Adjectives are modifying phrases. Modifying phrases can be omitted; they only describe something off-hand (as if they were in parentheses or something) and that’s it. They aren’t crucial to the sentence’s meaning. I’ll bold the actual subject and italicize the modifying phrase.</p>
<p>1) CORRECT: The Swiss psychologist Jean Piaget was the first scientist…
2) INCORRECT: The Swiss psychologist, Jean Piaget, was the first scientist…</p>
<p>In the first case, “the Swiss psychologist” is an adjective that modifies “Jean Piaget.” We know that we are talking about Jean Piaget, who just happens to be a Swiss psychologist. So we call her [the Swiss psychologist] Jean Piaget. We are giving “Jean Piaget” a profession here.</p>
<p>In the second case, “Jean Piaget” renames or modifies “the Swiss psychologist.” We know that we are talking about the Swiss psychologist, who just happens to be Jean Piaget. This does not make sense because that implies that there is only one Swiss psychologist in the world. We are giving “the Swiss psychologist” a name here.</p>