diff --git a/7t_trt/participants.json b/7t_trt/participants.json
index 693d4584e..a0c05a7fe 100644
--- a/7t_trt/participants.json
+++ b/7t_trt/participants.json
@@ -17,5 +17,9 @@
   "age_at_first_scan_years": {
     "LongName": "age_at_first_scan_years",
     "Units": "years"
+  },
+  "handedness": {
+    "LongName": "Edinburgh Handedness Inventory",
+    "Units": "arbitrary"
   }
-}
\ No newline at end of file
+}