diff --git a/py/20200221_experiment_scheduling.py b/py/20200221_experiment_scheduling.py
index 7eac5fc..9beec24 100644
--- a/py/20200221_experiment_scheduling.py
+++ b/py/20200221_experiment_scheduling.py
@@ -93,7 +93,7 @@
   return t
 
 # 3. games
-games = s.Tasks('Game',length=game_duration, num=n_sessions, is_group=False)
+games = s.Tasks('Game',length=game_duration, num=n_sessions, is_group=False, delay_cost=1)
 games += alt(sessions)
 
 # 3. questionnaires
@@ -103,9 +103,11 @@
 
   if q in prestudy_tasks:
     task += sessions[0] # first session
+    task.delay_cost = 2
     s += task < games
   elif q in poststudy_tasks:
     task += sessions[-1] # last session
+    task.delay_cost = -2
     s += games < task
   elif q in postgame_tasks:
     task += sessions