Sixteen hues sampled evenly around a near-perceptually-uniform hue circle, all at the same lightness and chroma, and all inside what your screen can actually show before it starts clipping.
Where this design comes from
In the Egyptian zar, the thread — khayt — is the distinctive drum rhythm belonging to each
spirit, and the kodia who leads the ceremony is expected to know the songs and rhythms of
each. She performs them one at a time and watches for a reaction, and the rhythm that produces one
identifies the spirit.
Look at the shape of that rather than at the metaphysics. A fixed enumerated set of stimuli.
Serial presentation. A response criterion. Classification by maximal differential response.
That is a within-person psychophysical protocol, and it was built centuries before anybody wrote
down a method section.
We are borrowing the method. We are not borrowing the cosmology. This page will name a
hue. It will never name a spirit, a Thread or a deity, and it does not map any
hue to one — not because that would be impolite, but because no instrument can do it and
the statement would be false.
The khayt-as-drum-rhythm account is the standard one and is consistent across
the sources read, but it is marked partially verified: El Hadidi (2016), Zar: Spirit
Possession, Music, and Healing Rituals in Egypt (AUC Press) is the scholarly source and has not
been read in full here. The protocol does not depend on it — it stands as psychophysics either way —
but this attribution does, and saying so is cheaper than implying otherwise.
What is going to happen, and what will be reported
You will be shown each of the 16 hues for
8 seconds and asked, after each, how much of a response it produced.
There is no right answer and no wrong one, and “nothing at all” is a real answer that is worth
giving.
Your response profile.The shape, across the whole set.
Whether it repeats.The agreement between your blocks, with the number
shown — and it is shown whether it is good or bad. Especially when it is bad.
Which hue reliably produced your largest response— and only
if the profile repeated and the peak held in a majority of blocks. If not, we say we cannot tell it
from noise, which is a real result and not a failure.
This result will never be worded as: “This is your Thread.”
Your key
Your browser made you a random key. We store a one-way hash of it, never the key. It is the only
thing linking this sitting to your next one — write it down.
…
Before you start
Under a minute. None of it is required, every question can be skipped, and
"prefer not to say" is recorded as itself rather than turned into a default. This is not
part of the exam and nothing here is scored.
What your screen cannot do, and why it does not sink this exam
Your display is not calibrated and cannot be.sRGB is a standard, not a description of your panel. Its actual primaries and transfer curve are unknown and unknowable from JavaScript, and auto-brightness means the display can change itself mid-session. Every exam here is therefore built as a within-person, within-display measurement.
Your screen cannot show every colour.An sRGB panel cannot display a saturated spectral green; where a stimulus falls outside the triangle the browser silently clips it to the edge. Clipping is not noise — it is a systematic compression that makes different people’s settings look more similar than they are.
The room you are in is part of the stimulus.A screen in a bright room has a grey veil over it: contrast falls, the black point rises, and your adaptation is set by the room rather than by anything we sent you.
We will never print a wavelength.Converting a screen colour to nanometres requires the display’s primaries, which we do not have. Any site that gives you a nanometre figure from a browser is making it up.
Every one of those is true and none of them is fixable from JavaScript. They are survivable here
for exactly one reason: the comparison is your own first block, on this screen, minutes
earlier. A display error that is present in both blocks cancels. A display error that is present in
only one of them is why we ask you not to change your brightness halfway through.
All sixteen hues sit inside what an sRGB panel can show before it clips, so none of
them is a compressed approximation of a colour we could not send you.
The sixteen hues
How much of a response did that produce?
nothing at alla great deal
And was it pleasant or unpleasant? (optional)
unpleasantpleasant
The other set
The same protocol runs over the sixteen rhythms.
The comparison between the two is the interesting part: a person whose rhythm profile repeats and
whose hue profile does not has learned something about themselves that neither run gives on its
own.
The rules this page is bound by
Report the measurement, not the category."Your VVIQ score was 19 out of 80. Scores at or below 24 are the range in which most published aphantasia research recruits participants." Never "you have aphantasia."
Name the reference class, every time.A percentile is meaningless without saying among whom. Ours is: among people who found this page and chose to take the test. That group is systematically enriched for exactly the traits being measured, because people who suspect something about themselves go looking.
Consistency, not confidence.For every instrument the second administration is part of the instrument. A one-shot result is a reading, not a finding.
Never route a result to anything consequential.No credential tier, no karma weight, no grant eligibility, no payment. The moment a score buys something, people optimise it and the data dies.
Coloured light is presented here as history and as published research, not as a treatment. This is not a medical device and not medical advice. Nothing here diagnoses, treats, cures or prevents any disease, no colour is matched to a condition, and no claim is made that light measures or restores anything about your body. Where the research is strong we say so; where the tradition’s claims are unsupported we say that too.