Module reference · ISO 17488

Detection response task

The DRT module runs a Red Scientific detection response task unit, plots reaction times as they arrive, and writes one row per stimulus with the reaction time the device measured.

Hardware

The DRT product page describes the kit and the method.

Quick reference

Reaction time: reaction_time_ms, measured on the device, 1 ms resolution
Miss: reaction_time_ms is -1: no press before the next stimulus
Line up with other modules: record_time_mono
ISO 17488 hit window: 100 to 2500 ms after onset. Applied by you in analysis, not by RSLogger

Getting started

Connect the unitPlug the wired DRT into a USB port, or plug the XBee coordinator in for a wireless DRT.
Enable the moduleCheck DRT in the Modules menu. RSLogger scans the serial ports and lists each unit in the Devices panel. Click the unit to connect it; its window opens and its indicator turns green. RSLogger reconnects it on the next start. For a wireless unit, click Rescan if it does not appear.
Set the timingFile > Configure… in the DRT window. Upload ISO loads the ISO 17488 values.
RecordStart a session and click Record. The device starts presenting stimuli and the window plots each response.

Stimulus types

The kit has three stimuli. All three plug into the same controller and the module does not need to know which is fitted.

Type	Description	Typical use
TDRTTactile	A vibration motor worn on the shoulder or collarbone. Places no demand on vision.	Studies of displays and touchscreens, where a visual stimulus would compete with the task under test.
HDRTHead-mounted	A red LED on a headband in the peripheral visual field. It moves with the head, so its visual angle stays constant.	Tasks where the head moves and the stimulus must stay in the same place relative to the eyes.
RDRTRemote	An LED fixed in the cabin, on the dashboard or A-pillar. Earlier literature calls this the peripheral detection task.	In-vehicle studies with a fixed reference point in the cabin.

The DRT window

DRT module window with a stimulus trace, a reaction time plot and the capture statistics — DRT window during a session. Misses are marked at zero on the reaction time plot.

The upper plot shows the stimulus state over the last 60 seconds and the lower plot marks each reaction time. Capture Stats below them show the stimulus count, the last reaction time or Miss, the number of button presses, and the battery level of a wireless unit. The menus are File (Configure…), View (Stimulus: ON and Stimulus: OFF, to test the stimulus by hand) and Help.

Configuration

File > Configure… opens the Runtime Parameters dialog. The values live on the device and survive power cycles.

Parameter	ISO value	Meaning
Lower ISI (ms)	3000	Shortest interval from one stimulus onset to the next.
Upper ISI (ms)	5000	Longest interval. The device draws each interval at random between the two.
Stimulus Duration (ms)	1000	How long the stimulus stays on if there is no response. A response turns it off at once.
Stimulus Intensity (%)	100	LED brightness or motor drive.

Upload ISO writes the four ISO 17488 values to the device. Upload Custom writes whatever is in the fields.

What is logged

The module writes one CSV per unit for the whole session, in the DRT folder, and appends one row for each stimulus.

OUTPUT PATH CSV

{session_dir}/DRT/{token}_DRT_dev_ttyacm0.csv

Column	Description
`reaction_time_ms`	Onset to first press, in milliseconds, measured on the device. -1 when there was no press before the next stimulus.
`responses`	Button presses between this stimulus and the next.
`device_time_offset`	Stimulus onset in milliseconds since the device started the experiment, on the device’s clock.
`trial`	The device’s stimulus count. It restarts at 1 each time you press Record, so tell trials apart by `label` or by the session’s control file.
`record_time_mono`, `record_time_unix`	Host time when the result message arrived. Use for lining up with other modules.
`stim_type`	Wired unit only. 1 for the standard stimulus. Standard firmware never writes 2.
`battery_percent`	Wireless unit only.

The data output reference lists all eleven columns in order.

Misses are data

A row with -1 is a stimulus the participant did not answer. ISO 17488 treats hit rate and reaction time as two separate measures, and both rise and fall with cognitive load, so keep the miss rows and report both.

How the reaction time is measured

The device measures the reaction time itself. Its firmware notes the time it switches the stimulus on and the time it sees the first button press, and reports the difference. Host latency does not enter into it. The two units do this differently, and the difference is worth knowing when you compare them.

	Wired DRT	Wireless DRT
Clock	Millisecond timer	Microsecond timer, rounded to 1 ms
Press detection	Polled through a switch debounce that reports a press once the contact has been steady for 5 ms	Hardware interrupt on the contact’s first edge, then a lockout against bounce
Effect on the value	Every reaction time is reported about 5 ms late. The offset is the same on every trial, so it cancels in comparisons between conditions on the same unit	No debounce delay
Connection	USB serial	XBee radio to a USB coordinator
Power	USB	Battery, level in `battery_percent`
Several units at once	Each unit on its own USB port gets its own window	Several units on one coordinator, each with its own window

These statements come from reading the firmware. Neither unit’s timing has been characterized on a bench, and no accuracy figure is claimed.

Applying the ISO 17488 window

ISO 17488 counts a response as a hit when it comes 100 to 2500 ms after onset. A response inside 100 ms is premature, and the standard excludes that stimulus from the hit rate. A response after 2500 ms does not count. RSLogger records the raw reaction time and leaves this classification to you:

PYTHON PY

import pandas as pd

drt = pd.read_csv("20260318_143022_DRT_dev_ttyacm0.csv")
rt = drt["reaction_time_ms"]

premature = rt.between(0, 99)
hit = rt.between(100, 2500)
scored = ~premature                       # ISO excludes premature stimuli from the hit rate

hit_rate = hit[scored].mean()
mean_rt = rt[hit].mean()                  # reaction time is reported over hits only

A row with -1 is a miss. A row with a reaction time above 2500 ms is also a miss under the standard, although the device recorded a press.

Troubleshooting

The unit is not detected

Confirm that it appears as a serial port: a COM port on Windows, /dev/ttyACM* on Linux, /dev/tty.* on macOS. If no port appears, try another cable. Some USB cables carry power only.

On Linux, your user must be in the dialout group to open the port. Log out and in after adding it.

No stimulus appears

Check that Stimulus Intensity is above 0 and Stimulus Duration is not 0. Check that the stimulus is plugged into the stimulus port on the controller. Stimuli are presented only while a trial is recording. View > Stimulus: ON turns the stimulus on by hand for a test.

Every stimulus is a miss

The response switch is not registering. Check that it is plugged into the response port and that Responses in Capture Stats counts up when you press it.

A wireless unit drops out

Keep the coordinator in range of the unit and away from large metal surfaces. Check battery_percent in the last rows written. Click Rescan in the Devices panel after the unit comes back.