diff --git a/learning.py b/learning.py
index df5d6fce3..f84017a87 100644
--- a/learning.py
+++ b/learning.py
@@ -35,6 +35,9 @@ def manhattan_distance(predictions, targets):
 def mean_boolean_error(predictions, targets):
     return mean(int(p != t) for p, t in zip(predictions, targets))
 
+def hamming_distance(predictions, targets):
+    return sum(p != t for p, t in zip(predictions, targets))
+
 # ______________________________________________________________________________