Sunday, March 16, 2008

Communicating with Highly Physically Disabled People

I just finished reading the book The Diving Bell and the Butterfly. It is a memoir dictated one letter at a time by Jean-Dominique Bauby, a stroke victim who suffered from locked-in syndrome.

Jean-Dominique was only able to communicate by blinking his left eye. An alphabet was developed that was re-ordered from the usual alphanumeric ordering, so that the most frequently used letters were at the beginning. To communicate, the speaker would cite each letter and Jean-Dominique would blink when the appropriate letter was said. Slowly, words would be built up and sentences would eventually form, conveying meaning. It was a tedious process and it had its drawbacks:
" "Want to play hangman?" asks Theophile, and I ache to tell him that I have enough on my plate playing quadriplegic. But my communication system disqualifies repartee: the keenest rapier grows dull and falls flat when it takes several minutes to thrust it home. By the time you strike, even you no longer understand what had seemed so witty before you started to dictate it letter by letter. So the rule is to avoid impulsive sallies. It deprives conversation of its sparkle, all those gems you bat back and forth like a ball - and I count this forced lack of humor one of the great drawbacks of my condition." (Pages 70 and 71, The Diving Bell and the Butterfly)

Since Jean-Dominique was a native French speaker, the letter frequencies in his special alphabet were based on the French language. The alphabet looked like this:


For the English language, the letter frequencies (which can be found here) would be:


It occurred to me that there had to be a more efficient manner to do this. I see two problems:

  • It takes a great deal of time to get to a letter deep into the alphabet. 
  • The deeper in the alphabet you go, the more likely it is that an error.

In order to improve communications speed, I came up with this alternate "tabular" method:

Note: Since the standard Latin alphabet has 26 letters, a six by five table left four empty spots. I chose letter pairs to fill those spots. The letter pairs were guessed at, as my brief searching was unable to turn up any letter pair frequency tables. I have no doubt that an exhaustive lexical analysis of the English language would turn up the true top four letter pairs. Some pairs like IE and EA are very common, but they are pretty cheap to create one letter at a time, so it's not worth using them in the far bottom corner where it takes more steps to get to them.

This alternative method works as a simple Cartesian coordinate system. That's fancy mathematics speak for "select the row and then select the column". To find the letter M, the letter selector starts at the top row and works down row by row, until the patient blinks when the second row is chosen. This means the patient could be interested in the letters T, I, R, M or B. The selector would then work across the columns until the patient blinks when the M character is chosen. In total, six stops were made to get to the M character. The old system would have required fourteen; more than twice as many. In addition, by locking the selector into a given row, the possibility for error is greatly reduced. If the selector picks the wrong row or misses the target letter, they will know they've done so because the patient never blinks by the end of the row. With the old system, the selector would have to go to the end of the entire alphabet to find that they've missed the letter.

To give you a better idea of the benefit of this system, here's the same table with the relative costs of getting to each letter added. The letter represents the target letter, the number represents the number of steps, or "cost", required to get to that letter and the number in parenthesis is the cost the old system required to get to that letter:

E - 2 (1)A - 3 (3)N - 4 (6)D - 5 (10)W - 6 (15)
T - 3 (2)I - 4 (5)R - 5 (9)M - 6 (14)B - 7 (20)
O - 4 (4)H - 5 (8)U - 6 (13)P - 7 (19)X - 8 (24)
S - 5 (7)C - 6 (12)Y - 7 (18)J - 8 (23)PH - 9 (27)
L - 6 (11)G - 7 (17)K - 8 (22)Z - 9 (26)LY - 10 (29)
F - 7 (16)V - 8 (21)Q - 9 (25)QU - 10 (38)RY - 11 (27)
Some immediate observations are that the letters E and T actually require one more step in this system than the old. In addition O and A cost the same in both systems. However, it should be noted that the overall cost savings is dramatic when you start creating whole words. For example. Let's take the following sentence (chosen from a random poster I saw at my Son's elementary school):

The cost breakdown is as follows:

WordOld CostNew Cost
Thus with the old system, it costs 70 letter stops to spell the test sentence. With the system I am proposing, it only takes 41. It is also important to note that the word SEE costs the same in both systems, which is an example of how the extra step to find the letters E and T are quickly absorbed by economies elsewhere.

Potential improvements on this would be to re-arrange the alphabet on a per patient basis. Since everyone uses a slightly different subset of their native language's words, their letter frequencies would likely be slightly different. If available, recordings and writings from the patient created prior to becoming disabled could be analyzed to alter the table layout. However, after the patient starts using the table, I would suggest that it not be altered unless absolutely necessary, as a familiarity will have been built up that will be difficult to overcome to take advantage of newer efficiencies. It would be interesting to study whether or not patients adapt their vocabulary to the table, thus removing any need to alter the table to introduce efficiencies after being introduced to it.

A potential objection to altering the table on a per patient basis prior to being introduced to it, would be that each patient should use the same letter table to keep communications uniform. I would overcome this objection with the idea that patients will not be using this system to talk directly to each other. This system would only be meant to facilitate communication between a disabled patient and an able bodied person who can work the board. The able bodied person working the board, should be able to adapt to different boards for different patients, especially considering that the incremental improvements in communications speed will far outweigh any inconvenience to the board operator. In addition, there is no reason why the intermediary could not be a computer, thus allowing similarly disabled patients to communicate with each other in real time. I wonder if it would be a positive thing for a patient to share their feelings with someone in the same situation?

It is important to note that this system is only useful for persons who already have the ability to read and can process information relatively normally. It is also only useful to those that have the ability to consistently gesture in a singular fashion, such as an eye blink, or some other "single bit" manner. If multiple gestures can be clearly and consistently mastered, there are much faster ways of communicating than the system that I am proposing. It would be very interesting to be able to study systems that apply to various numbers of feedback bits from the patient. As a general rule, the greater number of feedback bits available from the patient, the more robust and efficient the communication. I should coin the term CFB - Consistent Feedback Bits. A basic eye blink would be one CFB. An eye blink and a finger twitch, would be two CFBs and so on. The various systems of communicating could be indexed by CFBs. A specialist could assess the patients CFBs and perhaps use therapies to expand the number of CFBs, and then a system of communication could be chosen that best fits their unique situation. Again, many of these systems of communications would fall apart if the patient is simply cognitively unable to process information.

I believe that this system requires the ability to see out of at least one eye, but could possibly be used with a blind patient as long as they could hear well enough to memorize the table and give "single bit" feedback as they were learning. If the patient were blind and deaf, it may still be possible to communicate as long as they had relatively normal information processing abilities and could feedback to indicate to their teacher where they were in the learning process.


ydna said...

Is the speaker/author a "patient" in this context? The word strikes me as out of place here. (I realize I'm picking a nit.)

chuckwolber said...

Yes, the speaker/author is the patient.

(don't worry, picking nits is good, precise communications are essential when there are a lot of shades of meaning)