PARALLEL AND SEQUENTIAL PROCESS OF INFORMATION
When I described the pillars that analyze the visual information entering the visual cortex, I spoke not only of modularity, but also of the parallel activity of the modules. From the moment that each module works independently at the same time on the same flow of information, the management of the information is considered parallel. As the activity of each module occurs simultaneously, each module acts without waiting for the results of the analysis of the other modules. Imagine a patient who arrives at the emergency room of a hospital. Medical personnel will take blood and urine samples, for example. They will send what they have obtained to different laboratories, which will each analyze a specific aspect of those samples without waiting for the results of the other tests. During this time, the patient will be sent to radiology for more tests. The synthesis will be done later. Only at the moment of determining the diagnosis and the sequence of care will the attending physician know what test results are pertinent. That form of analysis is different from a sequential analysis procedure. Sequential analysis requires that each analysis is undertaken one after the other and only once the result of the previous analysis is known. This procedure is used in traditional causal models and logic.97 Take, for example, a laboratory that runs tests on blood samples:
1. Sequential analysis: In sequential analysis, one begins with what seems to be the most important analysis required for a certain diagnostic. Once this analysis has been carried out, the clinician may need a second analysis to specify his intuitive diagnostic. He will then carry out this second analysis and continue with this procedure until he can propose the best diagnostic possible. He may, for example, begin by analyzing the cholesterol, then the sugars, then the antibodies, then the concentration of red blood cells, then iron. He may find that the sudden weakness of a person is due to a lack of iron in the blood.
2. Modular and parallel analysis: To carry out these five tests, blood is placed into five separate test tubes. Each tube is placed in a different machine that analyzes a pertinent property (one for sugars, one for lipids, one for iron, etc.). A switch activates these five machines that carry out their test at the same time in parallel fashion. In general, a complete blood test measures about 20 variables of this type. The physician will receive, on paper or on a screen, the list of the results of these tests. He will subsequently evaluate which variables can be considered relevant. Sometimes, analytical software will also indicate if some combinations (low iron and low red blood cell count) require his attention.
The syllogism is an example of sequential reasoning:
If A = B,
And B = C,
Then A = C.
A parallel analysis of the syllogism made by the subroutines of a program runs according to the following procedure:
Module 1: Question: A = B? Answer: yes or no.
Module 2: Question: B = C? Answer: yes or no.
Module 3: If answer 1 and answer 2 = yes, then A = C; if answer 1 and 2 are not equal, then A and C are not equal.
In fact, in modular thinking, it is often simpler to have a routine that directly compares A and C without needing the answers from the two other modules. There is therefore no longer a logical linear thought, even if the empirical result is the same.