diff --git a/code/lydianlights/correlation-detective.py b/code/lydianlights/correlation-detective.py
new file mode 100644
index 0000000..76bc329
--- /dev/null
+++ b/code/lydianlights/correlation-detective.py
@@ -0,0 +1,115 @@
+import numpy as np
+
+# algorithm: correlation-detective
+# by: lydianlights
+
+TRIAL_PERIOD = 10
+CERTAINTY_THRESHOLD = 0.8
+CORRELATION_THRESHOLD = 0.65
+REVENGE_TIMER = 3
+
+# Try to predict whether our stimuli have an effect on the opponent, then try to take advantage
+def strategy(history, memory):
+  t = history.shape[1]
+  if memory == None:
+    memory = initMemory()
+  
+  if t < TRIAL_PERIOD:
+    return titForTat(history), memory
+
+  memory = updateMemory(history, memory, t)
+  defectPrediction, coopPrediction = calcPredictions(memory, t)
+
+  # we think opponent will coop when we defect -- take full advantage
+  if defectPrediction > CERTAINTY_THRESHOLD:
+    return 0, memory
+
+  # we think opponent will coop when we coop -- work together unless we have a grudge to settle
+  if coopPrediction > CERTAINTY_THRESHOLD:
+    if memory["grudge"] > 0 and memory["lastRevengeAt"] > REVENGE_TIMER:
+      return 0, memory
+    return 1, memory
+
+  # we think opponent will defect on us -- defect in return
+  if defectPrediction < -CERTAINTY_THRESHOLD or coopPrediction < -CERTAINTY_THRESHOLD:
+    return 0, memory
+
+  # we think the opponent is watching us but we're still unsure of their strategy
+  if abs(defectPrediction) > CORRELATION_THRESHOLD or abs(coopPrediction) > CORRELATION_THRESHOLD:
+    return titForTat(history), memory
+
+  # we think opponent is unpredictable, so treat them like a random agent
+  return 0, memory
+
+
+# === Memory === #
+def initMemory():
+  return {
+    "grudge": 0,
+    "lastRevengeAt": 0,
+    "defCausesDef": [],
+    "defCausesCoop": [],
+    "coopCausesDef": [],
+    "coopCausesCoop": [],
+  }
+
+def updateMemory(history, memory, t):
+  myStimulus = history[0, -2]
+  myPrev = history[0, -1]
+  oppPrev = history[1, -1]
+
+  if myStimulus == 0:
+    if oppPrev == 0:
+      memory["defCausesDef"].append(t)
+    elif oppPrev == 1:
+      memory["defCausesCoop"].append(t)
+  elif myStimulus == 1:
+    if oppPrev == 0:
+      memory["coopCausesDef"].append(t)
+    elif oppPrev == 1:
+      memory["coopCausesCoop"].append(t)
+
+  if myPrev == 1 and oppPrev == 0:
+    memory["grudge"] += 1
+  elif myPrev == 0 and oppPrev == 1:
+    memory["grudge"] -= 1
+    memory["lastRevengeAt"] = t
+
+  return memory
+
+
+# === Correlations === #
+def calcPredictions(memory, t):
+  defectSampleSize = len(memory["defCausesDef"]) + len(memory["defCausesCoop"])
+  coopSampleSize = len(memory["coopCausesDef"]) + len(memory["coopCausesCoop"])
+  correlations = (
+    createCorrelation(memory["defCausesDef"], defectSampleSize, t),
+    createCorrelation(memory["defCausesCoop"], defectSampleSize, t),
+    createCorrelation(memory["coopCausesDef"], coopSampleSize, t),
+    createCorrelation(memory["coopCausesCoop"], coopSampleSize, t),
+  )
+
+  # Map what we think will happen when we defect/coop to a value -1 to 1
+  # -1 means we think they will defect, 1 means we think they will cooperate, 0 means we are unsure
+  defectPrediction = correlations[1] - correlations[0]
+  coopPrediction = correlations[3] - correlations[2]
+
+  return defectPrediction, coopPrediction
+
+def createCorrelation(positives, sampleSize, t):
+  if sampleSize == 0:
+    return 0
+  
+  # Strength of predicted correlations goes down over time, guarding against inconsistency
+  strength = 0
+  for turnFound in positives:
+    turnsAgo = (t + 1) - turnFound
+    strength += 1 / turnsAgo
+  return len(positives) / sampleSize * np.tanh(strength)
+
+
+# === Strategies === #
+def titForTat(history):
+  if history.shape[1] > 0 and history[1, -1] == 0:
+    return 0
+  return 1