diff --git a/book-1-lesson-1.module b/book-1-lesson-1.module
index 19042e10..20d8a4ac 100644
--- a/book-1-lesson-1.module
+++ b/book-1-lesson-1.module
@@ -1259,7 +1259,7 @@ LINE: This is my chair. That's your chair.
 # Source: ST §That's Your Pen
 $DIALOGUE That's Your Pen
 ID: l1-s16
-INTRO: Two students sort out whose things are whose. Just listen and read along — no repeating this time.
+INTRO: Two students sort out whose things are whose. Notice the switch: A holds something up and asks "What's this?" — it's near A, so B answers "That's your pen" (near you, not me). "This" and "that" flip depending on who is speaking. Just listen and read along — no repeating this time.
 INSTRUCTION: Listen and read the questions and answers.
 
 StudentA: What's this?
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