Message Coding Scheme

What is a message coding scheme and what is it good for?

For sending arbitrary messages from wake world and also from sleep world, a coding scheme can be necessary. A coding scheme here describes a system by which arbitrary content can be transmitted using a limited way of communication. Most of the stimuli which can be incorporated into dreams and can thus be used for messaging from wake world to sleep world, as for example sinus tones, light flashes or tactile stimuli, are limited in their variability and thus need a coding scheme. An exception is the use of spoken words; however, it is unclear how successful correct incorporations of these can be achieved. Equally, transporting arbitrary messages from the sleep world to the wake world using body signaling needs a coding scheme, too.

Can you give an example for this?

A very old coding scheme which can be used for this purpose and which needs only an ON-OFF capability of a stimulus or body signal, is the Morse code. The Morse code defines for each letter of the alphabet a sign consisting of short and long ONs, separated by short OFFs within a letter, longer OFFs between letters and even longer OFFs between words (see Appendix B). Moreover, there exist Morse signs also for punctuation and for numbers. Since this coding scheme only needs ON-OFF capabilities of a signal, it can be applied to a number of sleep communication stimulus types and body signals. Table gives some examples. As can be seen, the same stimulus type or body signal can be used in various ways.

Stimulus type, body signal

Short ON

Long ON


Sinus tone

Short beep

Long beep

Stimulus muted

Sinus tone

High frequency beep

Low frequency beep

Stimulus muted

Light flash

Short light flash

Long light flash

Light turned off

Eye signal

Eye movement to the left and back to the center

Eye movement to the right and back to the center

No eye movement

Muscle signal

Contraction of left biceps, followed by relaxation

Contraction of right biceps, followed by relaxation

Relaxation of both biceps

Muscle signal

Short contraction of left biceps, followed by relaxation

Long contraction of left biceps, followed by relaxation

Relaxation of left biceps

Morse coding scheme applied on exemplary stimulus types and body signals

Can this be made more effective?

It is also possible to use coding schemes with more than two different signs instead of using Morse code in order to increase the speed of coding. If for instance a stimulus type or body signal with six different variations is used, all 26 letters of the alphabet and the numbers from 0 to 9 can be represented by a combination of only two signs (instead of up to 5 Morse signs). Application examples are: light flashes in six different colors, or six different tones; eye movements to the left, right, up, down, in a clockwise circle and in a counterclockwise circle, or contractions of six different muscles. Disadvantage of such a more complex coding scheme is that it is harder to learn, and more difficult to control than using Morse code.