Detection Response Task
The Detection Response Task (DRT) module measures cognitive workload by recording reaction time to a periodic stimulus — typically a red LED — while the participant performs a primary task such as driving.
Looking for the hardware? See the Detection Response Task product page.
- Primary metric
reaction_time_ms- Miss recorded as
-1- Cross-module sync
record_time_mono- Valid response window
- 100–2500 ms (ISO 17488)
Getting Started
Bring a DRT online and start collecting reaction-time data in four steps.
- Connect the DRTPlug the DRT into the host machine via USB, or connect wirelessly over XBee for the wDRT.
- Enable the DRT module in RSLoggerOpen the module panel and toggle Detection Response Task on. RSLogger will scan the serial ports and bind the device.
- Configure timing parametersSet the inter-stimulus interval, stimulus duration, and intensity, or click ISO Defaults to load the ISO 17488 values.
- Start a recording sessionBegin the session. Stimuli fire at the configured intervals and reaction times stream to disk in real time.
Stimulus Configurations
The DRT supports three stimulus presentations. Each maps to a standardized configuration in the human factors literature.
| Config | Description | Use case |
|---|---|---|
| TDRTTactile | Vibrating motor worn on the shoulder or collar. Avoids interference with the participant’s visual field. | Studies of visual displays and touchscreens, where a visual stimulus would compete with the primary task. |
| HDRTHead-Mounted | Red LED mounted on a lightweight headband in peripheral vision. Moves with the head for a consistent visual angle. | Free-moving tasks where the stimulus must stay fixed relative to the participant’s gaze. |
| RDRT / PDTRemote | Fixed LED in the peripheral field, mounted on the dash or A-pillar. Also known as the Peripheral Detection Task. | In-vehicle studies with a fixed reference point relative to the cabin. |
User Interface
The DRT panel gives you live visibility into stimulus timing and participant response as the session runs.
The interface has three regions. A real-time chart plots two tracks across a 60-second scrolling window: the upper track shows the stimulus state (ON/OFF), and the lower track shows reaction-time bars for each response. A results panel reports running hit rate, miss rate, and mean reaction time. A device menu lists connected DRTs and exposes the timing parameters and ISO Defaults button.
Configuration
Timing Parameters
Defaults follow ISO 17488. Click ISO Defaults to restore these values at any time.
| Parameter | Default | Notes |
|---|---|---|
| Lower ISI | 3000 ms | Lower bound of the inter-stimulus interval. |
| Upper ISI | 5000 ms | Stimuli appear at random 3–5 s intervals. |
| Stimulus Duration | 1000 ms | How long the stimulus stays on if no response is given. |
| Intensity | 100% | LED brightness or tactor amplitude. |
Response Classification (ISO 17488)
Each response is classified by the latency window in which it falls.
| Window | Classification | Recorded |
|---|---|---|
| < 100 ms | Anticipatory | excluded |
| 100–2500 ms | Valid | hit |
| > 2500 ms or none | Miss | reaction_time_ms = -1 |
Data Output
Each DRT writes a CSV file under the session directory, one file per device.
{session_dir}/DRT/{prefix}_DRT_{device_id}.csv| Column | Description |
|---|---|
reaction_time_ms | Primary metric. Latency from stimulus onset to response, in milliseconds. -1 denotes a miss. |
record_time_mono | Monotonic host timestamp used for cross-module synchronization. |
trial | Sequential trial index within the session. |
stim_state | Stimulus ON/OFF state at the sample. |
battery_percent | Remaining battery charge. wDRT only. |
Interpreting reaction time: ~250 ms ≈ low load · ~400 ms ≈ moderate load · ~700 ms ≈ high load · -1 = miss.
A miss is not a dropped sample. As cognitive load rises, participants miss more stimuli, so hit rate and miss rate are core outcome measures alongside reaction time. Report them together; a low miss rate with rising reaction time tells a different story than a high miss rate.
Host timestamps carry roughly 20–50 ms of delay from USB and OS scheduling. For sub-millisecond timing, use the device’s own clock fields where available.
Device Types
RSLogger supports both the wired DRT and the wireless wDRT. The wDRT trades a USB tether for an XBee radio and an onboard battery, with tighter timing.
| Feature | DRT (USB) | wDRT (wireless) |
|---|---|---|
| Timing accuracy | ±5–7 ms | ±1–3 ms |
| Connection | USB serial | XBee wireless |
| Battery | No | Yes |
| Multi-device | Limited | Yes |
| Serial port | COM* / /dev/tty.* / /dev/ttyACM* | |
Troubleshooting
DRT not detected
Confirm the device appears as a serial port on the host (COM* on Windows, /dev/ttyACM* on Linux, /dev/tty.* on macOS). Replace the USB cable if no port enumerates, then re-scan from the device menu.
On Linux, verify your user is in the dialout group so RSLogger can open the port.
No stimulus appears
Check that Intensity is above 0% and that Stimulus Duration is non-zero. For TDRT, confirm the tactor is seated against the shoulder; for HDRT/RDRT, confirm the LED is plugged into the stimulus port. A session must be running for stimuli to fire.
All responses recorded as misses
This usually means the response button is not registering. Verify the micro-switch is connected and that responses are landing inside the 100–2500 ms valid window — presses faster than 100 ms are classified as anticipatory and excluded, not counted as hits.
wDRT connection drops
The XBee link is rated to 30 m line-of-sight. Keep the coordinator radio within range and clear of obstructions and large metal surfaces. Check battery_percent in the results panel; a low battery degrades the radio before the device powers down.