Day 1, part 4: contact doesn't stay, and what research says about eyes
In short
- Contact faded within about 15 minutes as the skin dried.
- The eye check now checks contact first and saves its recording.
- Research: the gold standard for eye signals is EOG, with electrodes beside the eyes.
On this page
The first eye checks with a real headband
Two runs of the eye check, both 0 of 3 blinks and 0 of 4 eye movements. Before blaming the eyes, we looked at the data again.
Contact changes from minute to minute
| Sensor | 15:11, forehead just dampened | 15:27, sixteen minutes later |
|---|---|---|
| AF7, left forehead | touching skin | identical to AF8, 32% mains hum |
| AF8, right forehead | touching skin | identical to AF7, 32% mains hum |
| TP9, left ear | no contact | still floating |
| TP10, right ear | no contact | touching skin |
As the water dried, the forehead sensors went back to behaving like one antenna. You cannot see eyes through sensors that aren’t touching, so the eye check never stood a chance.
This is the core problem for a whole night: with this headband and this skin, dry contact does not hold. Moisture helps for a few minutes, then fades.
What we changed
- The eye check now shows the forehead contact before it starts and warns when AF7 or AF8 is below 80%, instead of running a test that can’t succeed.
- It saves its recording (AF7, AF8 and the exact time of every prompt) to
Documents/OpenLucid/eyecheck-*.csv, so a failed check can be analyzed. - Two fixes in how it judges: the filter no longer starts with a jolt (raw EEG begins hundreds of microvolts from zero), and a blink is measured against the moment just before it, so a drifting sensor can’t hide it.
What the research standard says
We asked: how does science record eye movements during sleep, and what can a home project realistically use? The full answer, with sources and prices, is on the research page. The short version:
- Sleep labs record eye movements with EOG: two electrodes beside the outer corners of the eyes. Lucid-dream research has verified the left-right signal this way since 1981. A horizontal EOG is the gold standard.
- A forehead headband like the Muse sees eye movements only approximately. One independent study found the Muse S scores REM sleep well against a sleep lab, but nobody has published a test of left-right signal detection on a consumer headband. That is open territory, and worth testing ourselves.
- A cheap way to get real EOG at home: stick-on electrodes beside the eyes with an open amplifier (OpenBCI, or an educational kit like BITalino). Battery-powered only, never connected to a charging laptop.
Next
- Try the eye check again right after dampening the forehead, while both forehead sensors are green.
- Decide whether to add a real EOG channel next to the Muse, to test how well the forehead sees what the EOG sees.