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Jun25-10, 09:08 PM
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Nice post and interesting results, you said,
The variations are so subtle, complicated and mostly so continuous that it's hard to know what to time.
I agree, as an adaptation we could try using powerpoint, create slides with words, with timed unmasking of words and sequences of letters using different widths and time between letters, (this would ensure consistency and repeatability to the test). This is the long hard way to do things but is the most flexible.

Or use an online color-grapheme test if one is available (which may not be as flexible as we would like, a tradeoff). There are (at least) two more variables to consider, one, eye tracking, after reading the article in full I realize that there are many things to consider, the most important was the way the eyes process move to distinguish and then process data, through fixation and saccade except below:
Humans and other animals do not look at a scene in fixed steadiness; instead, the eyes move around, locating interesting parts of the scene and building up a mental 'map' corresponding to the scene. One reason for the saccadic movement of the human eye is that the central part of the retina—known as the fovea—plays a critical role in resolving objects. By moving the eye so that small parts of a scene can be sensed with greater resolution, body resources can be used more efficiently.

In addition, the human eye is in a constant state of vibration, oscillating back and forth at a rate of about 30–70 Hz. These microsaccades are tiny movements, roughly 20 arcseconds (one five thousandth of a degree) in excursion and are completely imperceptible under normal circumstances. They serve to refresh the image being cast onto the rod cells and cone cells at the back of the eye. Without microsaccades, staring fixedly at something would cause the vision to cease after a few seconds, since rods and cones respond only to changes in luminance.

Timing and kinematics:
Saccades are the fastest movements produced by the human body. The peak angular speed of the eye during a saccade reaches up to 1000°/sec in monkeys (somewhat less in humans). Saccades to an unexpected stimulus normally take about 200 milliseconds (ms) to initiate, and then last from about 20–200 ms, depending on their amplitude (20–30 ms is typical in language reading). Under certain laboratory circumstances, the latency of, or reaction time to, saccade production can be cut nearly in half (express saccades). These saccades are generated by a neuronal mechanism that bypasses time-consuming circuits and activate the eye muscles more directly.[3][4]

The amplitude of a saccade is the angular distance the eye travels during the movement. For amplitudes up to about 60°, the velocity of a saccade linearly depends on the amplitude (the so called "saccadic main sequence"). For instance, a 10° amplitude is associated with a velocity of 300°/sec, and 30° is associated with 500°/sec. In saccades larger than 60°, the peak velocity starts to plateau (nonlinearly) toward the maximum velocity attainable by the eye.

Saccades may rotate the eyes in any direction to relocate gaze direction (the direction of sight that corresponds to the fovea), but normally saccades do not rotate the eyes torsionally. (Torsion is clockwise or counterclockwise rotation around the line of sight when the eye is at its central primary position; defined this way, Listing's law says that when the head is motionless, torsion is kept at zero.)

Head-fixed saccades can have amplitudes of up to 90° (from one edge of the oculomotor range to the other), but in normal conditions saccades are far smaller, and any shift of gaze larger than about 20° is accompanied by a head movement. During such gaze saccades, first the eye produces a saccade to get gaze on target, whereas the head follows more slowly and the vestibulo-ocular reflex causes the eyes to roll back in the head to keep gaze on the target. During these head movements Listing's law is no longer obeyed.

Saccades, as well as microsaccades, can be distinguished from other eye movements (ocular tremor, ocular drift, smooth pursuit) using their ballistic nature: their top velocity is proportional to their length. This property can be used in algorithms for saccade detection in eye tracking data.
In addition if you look at this figure: see attached thumbnail: you will see the fixation times vary, for instance in the fourth line down, after "syd-" the eye slowed to analyze the hypen and space after it. Interesting...

The second issue is environment you test in, preferably a comfortable place with few distractions.

You also said,
The letters of RED stay quite distinct in the various arrangements I've set up, with just a little bit of bleed through of the red E to the R
that is interesting because for you red is your most predominant color, maybe it is "most quickly primed in your visual cortex", you said it was "quite distinct".

A lot to consider and I think you will agree not an easy thing to do after taking a peek a "bit deeper under the covers", I for one appreciate a more detailed understanding of how we visually acquire and process information, which can't be a bad thing, right ? hehe.


All of what follows is my on-line search for a test close to the one we have in mind. A scary thought just came over me, what if no one has ever done this test before, hmmm.

I found this pdf doc by Dr Cytowic including results from: "A new measure: the speeded congruency test" but this was only for recognizing individual letters. You may find this interesting because it shows with 1 to 2 ms accuracy how synesthetes differentiate individual letters on various levels of shaded backgrounds.

You may find this interesting as well: Grapheme-Color Synesthesia Mapper where all people reading this thread can take the test and then record for posterity their personal maps !
There are about two dozen or so there right now. I found it interesting, (assuming of course that most of the testers did not lie cheat) that there were some "fragmentary associations". This is consistent with waht experience for sound -> color, only certain frequency ranges played a specific way for a specific duration cause the sensation.

I also found this: The Synesthesia Battery From a quick scan of it, it doesn't seem to have the test we are trying to accomplish.

I can't say for certain, but after a substantial time of not finding a similar test, then it's back to doing it the hard way. What do you think, RasalHague, should I play with Powerpoint to see if I can come up with automated timed slides ? Do you have any creative ideas ? I am open to them, or from anyone else following this thread ?


P.S. I will be away for the next two days without computer access so, please don't get the wrong impression, I will check back in on Sunday evening. Thanks...
Attached Thumbnails
eye tracking.jpg