diff --git a/js/common/NaturalSelectionConstants.js b/js/common/NaturalSelectionConstants.js
index 91db75a1..4841bf40 100644
--- a/js/common/NaturalSelectionConstants.js
+++ b/js/common/NaturalSelectionConstants.js
@@ -58,7 +58,9 @@ const NaturalSelectionConstants = {
     xMargin: 6,
     yMargin: 4,
     touchAreaXDilation: 10,
-    touchAreaYDilation: 6
+    touchAreaYDilation: 6,
+    mouseAreaXDilation: 5,
+    mouseAreaYDilation: 3
   },
 
   // Checkbox
diff --git a/js/common/view/proportions/ProportionsGenerationSpinner.js b/js/common/view/proportions/ProportionsGenerationSpinner.js
index 818661f5..6887feb0 100644
--- a/js/common/view/proportions/ProportionsGenerationSpinner.js
+++ b/js/common/view/proportions/ProportionsGenerationSpinner.js
@@ -30,6 +30,10 @@ class ProportionsGenerationSpinner extends NumberSpinner {
       // NumberSpinner options
       xSpacing: 10,
       arrowsPosition: 'leftRight',
+      touchAreaXDilation: 20,
+      touchAreaYDilation: 10,
+      mouseAreaXDilation: 10,
+      mouseAreaYDilation: 5,
       numberDisplayOptions: {
         valuePattern: naturalSelectionStrings.generationValue,
         align: 'center',