diff --git a/js/common/model/AreaUnderCurveScrubber.ts b/js/common/model/AreaUnderCurveScrubber.ts
index 22bffe5d..0415cf4b 100644
--- a/js/common/model/AreaUnderCurveScrubber.ts
+++ b/js/common/model/AreaUnderCurveScrubber.ts
@@ -1,7 +1,8 @@
 // Copyright 2023, University of Colorado Boulder
 
 /**
- * AreaUnderCurveScrubber is the model element for the area-under-curve scrubber.
+ * AreaUnderCurveScrubber is the model element for the area-under-curve scrubber. It can be moved horizontally,
+ * and the accumulated area (or 'net signed area') is the area between x=0 and the scrubber's x position.
  *
  * @author Chris Malley (PixelZoom, Inc.)
  */
diff --git a/js/common/model/TangentScrubber.ts b/js/common/model/TangentScrubber.ts
index eccbc6fa..0e06fa5a 100644
--- a/js/common/model/TangentScrubber.ts
+++ b/js/common/model/TangentScrubber.ts
@@ -1,7 +1,8 @@
 // Copyright 2023, University of Colorado Boulder
 
 /**
- * TangentScrubber is the model element for the tangent scrubber.
+ * TangentScrubber is the model element for the tangent scrubber. It can be moved horizontally to position the
+ * tangent line on the original curve.
  *
  * @author Chris Malley (PixelZoom, Inc.)
  */