diff --git a/genann.c b/genann.c
index b05fa4f..f707476 100644
--- a/genann.c
+++ b/genann.c
@@ -201,6 +201,15 @@ void genann_randomize(genann *ann) {
     }
 }
 
+void genann_random_tweak(genann *ann, double max) {
+    int i;
+    for (i = 0; i < ann->total_weights; ++i) {
+        /* -max <= r <= max */
+        double r = (GENANN_RANDOM() - 0.5) * 2 * max;
+        ann->weight[i] += r;
+    }
+}
+
 
 void genann_free(genann *ann) {
     /* The weight, output, and delta pointers go to the same buffer. */
diff --git a/genann.h b/genann.h
index e4b7383..a9baf6d 100644
--- a/genann.h
+++ b/genann.h
@@ -79,6 +79,9 @@ genann *genann_read(FILE *in);
 /* Sets weights randomly. Called by init. */
 void genann_randomize(genann *ann);
 
+/* Modifies the weights randomly, with max as a threshold */
+void genann_random_tweak(genann *ann, double max);
+
 /* Returns a new copy of ann. */
 genann *genann_copy(genann const *ann);