diff --git a/concordia/agents/basic_agent.py b/concordia/agents/basic_agent.py
index 43f4c554..772cc5d4 100644
--- a/concordia/agents/basic_agent.py
+++ b/concordia/agents/basic_agent.py
@@ -88,6 +88,7 @@ def __init__(
     self._user_controlled = user_controlled
     self._update_interval = update_interval
 
+    self._conversation_prefix = ''
     self._under_interrogation = False
     self._state_lock = threading.Lock()
 
@@ -287,7 +288,22 @@ def get_externality(externality):
 
     return output
 
+  def observe_latest(self, conversation: str):
+    # If the prefix is not found then `find` returns -1.
+    prefix_start_index = conversation.find(self._conversation_prefix)
+    if prefix_start_index >= 0:
+      # Get the part of the conversation the agent heard since their last turn.
+      start_index = prefix_start_index + len(self._conversation_prefix)
+      conversation_suffix = conversation[start_index:]
+      # Replace newline characters with commas.
+      conversation_suffix = conversation_suffix.replace('\n', ', ')
+      # Observe the new part of the conversation.
+      self.observe(conversation_suffix)
+      # Store the whole conversation thus far as the new prefix.
+      self._conversation_prefix = conversation
+
   def say(self, conversation: str) -> str:
+    self.observe_latest(conversation)
     convo_context = (
         f'{self._agent_name} is in the following'
         f' conversation:\n{conversation}\n'