In the next experiment {CA-2, CA-3}, interaction (computation) was activated whenever CA-1[count] was 23 (marked by black dots). Between these events, CA-4 evolved on its own.

Process and system computation

The black lines in the first image  mark the computation (interaction) of the entire system, including the stem process which is not shown. The system proceeds from left to right. Each process continually computes its next state, which is called here process computation . Most states do not interact, like the one marked by the red line (system state = i). Two interacting states, or system computations are marked by black lines.

Although the processes are depicted  here discretely, in the model they are joined together. Each system state consists of a string of numbers which are updated by process computations. If following this update some processes interact, the  procedure is called here system computation. In the present example system computation followed the addition rule: CA-4 = CA-2 + CA-3. which was triggered by the stem process.

Stimulus and response

This rule is hardwired into the stem process and triggered when its cell count is 25.  By setting a different triggering condition,  stem process may activate the addition rule more often, like in the second experiment. When turning off its trigger, the system stops computing, and becomes isolated. It may be aroused again by an environmental stimulus, which triggers a computation conceived by us (the observer), as response.

Gene translation

CA-4=CA-2+CA-3 may be regarded as  system gene, stored in the stem process, which when activated is translated into its appropriate phenotype.  In this context, CA-4=CA-2+CA-3 is not an equation but an option.