diff --git a/sktalk/corpus/conversation.py b/sktalk/corpus/conversation.py
index 0b90abf..2af1580 100644
--- a/sktalk/corpus/conversation.py
+++ b/sktalk/corpus/conversation.py
@@ -120,25 +120,17 @@ def _subconversation(self,
                 "`time_or_index` must be either 'time' or 'index'")
         return Conversation(utterances=returned_utterances)
 
-        # TODO should metadata be part of this?
-        return Conversation(returned_utterances, self.metadata)
-
-    def _time_to_next(self) -> int:
-        # if len(self.utterances) != 2:
-        #     return None
-        try:
-            return self.utterances[0].until(self.utterances[1])
-        except (TypeError, IndexError):
-            return None
-
-    def _dyadic(self) -> bool:
-        participants = [u.participant for u in self.utterances]
-        return len(set(participants)) == 2
+    def _count_participants(self) -> int:
+        """Count the number of participants in a conversation
+
+        Importantly: if one of the utterances has no participant, it is counted
+        as a separate participant (None).
 
-    CONVERSATION_FUNCTIONS = {
-        "dyadic": _dyadic,
-        "time_to_next": _time_to_next,
-    }
+        Returns:
+            int: number of participants
+        """
+        participants = [u.participant for u in self.utterances]
+        return len(set(participants))
 
     def apply(self, field, **kwargs):
         """
diff --git a/tests/corpus/test_conversation.py b/tests/corpus/test_conversation.py
index e90a284..b4cf81b 100644
--- a/tests/corpus/test_conversation.py
+++ b/tests/corpus/test_conversation.py
@@ -99,15 +99,9 @@ def test_overlap(self):
         assert not Conversation.overlap(
             70, 80, [90, 110])  # utterance after window
 
-    def test_dyadic(self, convo):
-        assert not convo._dyadic()
-        convo2 = convo.subconversation(0, 2)
-        assert convo2._dyadic()
-        convo3 = convo.subconversation(0)
-        assert not convo3._dyadic()
-
-    def test_apply_dyadic(self, convo):
-        convo.apply("dyadic", before=1)
-        assert convo.utterances[0].dyadic
-        assert convo.utterances[2].dyadic
-        assert not convo.utterances[8].dyadic
+    def test_count_participants(self, convo):
+        assert convo._count_participants() == 3
+        convo2 = convo._subconversation(index=0, before=2)
+        assert convo2._count_participants() == 2
+        convo3 = convo._subconversation(index=0)
+        assert convo3._count_participants() == 1