diff --git a/CHANGELOG.md b/CHANGELOG.md
index eb9bde6..9f2b51b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- **Trials without a response in Visiomode 0.5+ sessions.** Newer Visiomode versions
+  record misses and correct rejections as a response named `"none"`, with the trial
+  timeout (4–10 s) as the response time. These trials were treated as having a
+  response, so the timeout was counted as a reaction time in the session and subject
+  RT metrics and report plots, the trials got a touch position of 0, and gonogo
+  regressors gave them a cued lever push response regressor instead of the hold
+  regressor. They are now treated as having no response
+  (empty `response`, `response_time` and position). `session.summary()` also blanks
+  `"none"` responses in trials CSVs written by earlier versions, so `visiomode-analysis
+  subject` gives correct RTs without re-running `session`. Lever push durations were
+  not affected.
+
 ## [0.4.0] - 2026-10-02
 
 ### Added
diff --git a/src/visiomode_analysis/session/__init__.py b/src/visiomode_analysis/session/__init__.py
index 4d56fad..6af4af4 100644
--- a/src/visiomode_analysis/session/__init__.py
+++ b/src/visiomode_analysis/session/__init__.py
@@ -57,6 +57,10 @@
 # outcome vocabulary so downstream logic only has to deal with one set of labels.
 LEGACY_OUTCOME_LABELS = {"hit": "correct", "false_alarm": "incorrect", "miss": "no_response"}
 
+# Newer Visiomode versions (0.5+) record a trial without a response (a miss or correct rejection) as a response with
+# this name, with the trial timeout as its response time. Older versions leave the response out instead.
+NO_RESPONSE_NAME = "none"
+
 # Companion file holding the duration (ms) of every lever push in a session, one row per push in trial order.
 LEVER_DURATIONS_SUFFIX = "_lever-durations.csv"
 LEVER_DURATION = "lever_duration"
@@ -397,6 +401,20 @@ def _lever_duration_summary(df: pd.DataFrame) -> dict[str, float]:
     return fields
 
 
+def _blank_none_responses(df: pd.DataFrame) -> pd.DataFrame:
+    """Blank out the response and response time of trials whose response is `NO_RESPONSE_NAME`.
+
+    `_flatten_trials` already does this for trials parsed from a JSON; this covers trials CSVs written by versions
+    before 0.4.1, which kept the "none" response and its timeout response time.
+    """
+    no_response = df["response"] == NO_RESPONSE_NAME
+    if not no_response.any():
+        return df
+    df = df.copy()
+    df.loc[no_response, ["response", "response_time"]] = np.nan
+    return df
+
+
 def get_rts(path: str, sdt_type=None, include_corrections=True) -> npt.NDArray:
     return _select_rts(get_trials(path=path), sdt_type=sdt_type, include_corrections=include_corrections)
 
@@ -427,7 +445,7 @@ def summary(path: str | pd.DataFrame, lever_durations: str | None = None) -> dic
         metadata = get_metadata(path)
         df = get_trials(path, lever_durations=lever_durations)
     else:
-        df = path if isinstance(path, pd.DataFrame) else pd.read_csv(path)
+        df = _blank_none_responses(path if isinstance(path, pd.DataFrame) else pd.read_csv(path))
         metadata = {
             "animal_id": df["animal_id"].iloc[0],
             "session_date": df["session_date"].iloc[0],
@@ -839,11 +857,23 @@ def _normalise_legacy_outcome(trial: Any) -> Any:
     return {**trial, "outcome": LEGACY_OUTCOME_LABELS.get(trial["outcome"], trial["outcome"])}
 
 
+def _normalise_no_response(trial: Any) -> Any:
+    """Return a copy of a raw trial with a `NO_RESPONSE_NAME` response rewritten the way older Visiomode versions
+    record no response: no response object and a response time of -1.
+
+    Done up front so the response, response time, touch position, stimulus reconstruction and SDT inference in
+    `_flatten_trials` all treat the trial as having no response, rather than counting the timeout as a reaction time.
+    """
+    if (trial.get("response") or {}).get("name") == NO_RESPONSE_NAME:
+        return {**trial, "response": None, "response_time": -1}
+    return trial
+
+
 def _flatten_trials(session: dict, metadata: dict) -> Iterator[dict]:
     session_start_time = datetime.datetime.fromisoformat(metadata.get("session_start_time", ""))
 
     for trial in session.get("trials", []):
-        trial = _normalise_legacy_outcome(trial)
+        trial = _normalise_no_response(_normalise_legacy_outcome(trial))
 
         start_time = (datetime.datetime.fromisoformat(trial["timestamp"]) - session_start_time).total_seconds()
 
diff --git a/tests/test_flatten_trials.py b/tests/test_flatten_trials.py
index d50f616..210ae9f 100644
--- a/tests/test_flatten_trials.py
+++ b/tests/test_flatten_trials.py
@@ -1,10 +1,12 @@
-"""Tests for `session._flatten_trials`'s handling of older Visiomode JSON formats: sessions
+"""Tests for `session._flatten_trials`'s handling of different Visiomode JSON formats: sessions
 recorded before an explicit `stimulus`/`sdt_type` field existed on each trial, where the presented
 stimulus and signal-detection classification instead have to be reconstructed from the trial's
-`outcome`/`response` and the session-level `stimuli` metadata.
+`outcome`/`response` and the session-level `stimuli` metadata, and newer (0.5+) sessions that record
+a trial without a response as a response named "none".
 """
 
 import numpy as np
+import pytest
 
 BASE_TRIAL = dict(
     timestamp="2022-01-01T00:00:01",
@@ -172,3 +174,59 @@ def test_legacy_other_protocol_uses_raw_stimuli_dict_unchanged(flatten_trial):
     assert trial["target_id"] == "movinggrating"
     assert trial["distractor_id"] == "isoluminantgray"
     assert "stim_id" not in trial
+
+
+# -- Visiomode 0.5+ records "no response" as a response named "none", with the trial timeout as its response time. --
+
+NEWER_STIMULUS = {"id": "movinggrating", "common_name": "Moving Grating"}
+
+
+@pytest.mark.parametrize(
+    "outcome, sdt_type, timeout",
+    [("no_response", "miss", 10.001618658035703), ("correct", "correct_rejection", 4.000969302495185)],
+)
+def test_none_response_is_treated_as_no_response(flatten_trial, outcome, sdt_type, timeout):
+    trial = flatten_trial(
+        {
+            **BASE_TRIAL,
+            "outcome": outcome,
+            "sdt_type": sdt_type,
+            "response": {"name": "none"},
+            "response_time": timeout,
+            "stimulus": NEWER_STIMULUS,
+        }
+    )
+
+    assert trial["response"] is None
+    # The timeout is not a reaction time.
+    assert np.isnan(trial["response_time"])
+    assert trial["pos_x"] is None and trial["pos_y"] is None
+    assert trial["dist_x"] is None and trial["dist_y"] is None
+    assert trial["sdt_type"] == sdt_type
+    # No response timestamp, so the trial runs to the end of the stimulus.
+    assert trial["stop_time"] == pytest.approx(1.0 + BASE_TRIAL["iti"] + 4.0)
+
+
+def test_named_lever_push_response_keeps_its_response_time(flatten_trial):
+    trial = flatten_trial(
+        {
+            **BASE_TRIAL,
+            "sdt_type": "hit",
+            "response": {"name": "leverpush", "timestamp": "2022-01-01T00:00:08", "pos_x": 400.0, "pos_y": 240.0},
+            "response_time": 2.23,
+            "stimulus": NEWER_STIMULUS,
+        }
+    )
+
+    assert trial["response"] == "leverpush"
+    assert trial["response_time"] == pytest.approx(2.23)
+    assert trial["pos_x"] == 400.0
+
+
+def test_none_response_is_normalised_before_sdt_inference(flatten_trial):
+    # Without an explicit sdt_type, a "none" response must still be read as no response,
+    # so a correct gonogo trial is a correct rejection rather than a hit.
+    trial = flatten_trial({**BASE_TRIAL, "outcome": "correct", "response": {"name": "none"}, "response_time": 4.0})
+
+    assert trial["sdt_type"] == "correct_rejection"
+    assert trial["stim_id"] == "isoluminantgray"
diff --git a/tests/test_session.py b/tests/test_session.py
index 3ff9f76..e074951 100644
--- a/tests/test_session.py
+++ b/tests/test_session.py
@@ -512,3 +512,21 @@ def test_summary_reads_metadata_from_a_filtered_trials_dataframe(gonogo_session_
 
     assert result["animal_id"] == "MM229"
     assert result["protocol"] == "gonogo"
+
+
+def test_summary_ignores_none_responses_in_trials_csvs_written_by_older_versions(tmp_path, write_trials_csv):
+    # Trials CSVs written before 0.4.1 kept Visiomode's "none" response with the timeout as its response time.
+    rows = [
+        dict(outcome="correct", correction=False, sdt_type="hit", response_time=0.5, response="leverpush"),
+        dict(outcome="incorrect", correction=False, sdt_type="false_alarm", response_time=0.7, response="leverpush"),
+        dict(outcome="no_response", correction=False, sdt_type="miss", response_time=10.0, response="none"),
+        dict(outcome="correct", correction=False, sdt_type="correct_rejection", response_time=4.0, response="none"),
+    ]
+    csv_path = write_trials_csv(tmp_path, "trials.csv", "A1", "2022-01-01", "gonogo", "expX", rows=rows)
+
+    result = session.summary(csv_path)
+
+    assert result["rt"] == pytest.approx(0.6)
+    assert result["rt_wc"] == pytest.approx(0.6)
+    assert result["rt_iqr"] == pytest.approx(0.1)
+    assert result["misses"] == 1 and result["correct_rejections"] == 1