Learning

     Learning is an optional feature in an intelligent system. An intelligent system that knows everything need not learn.

But the amount of knowledge in this universe is exponentially more than atoms. So no systems can have a marked answer to a marked question for every knowledge.

Learning is the ability of a system to change its configuration. It can change its algorithm.


    There are other metrics like effeciency of learning, its precision and accuracy. But that is for later on.


   Why is learning important in a system? It allows the system to pick up knowledge from its immediate surroundings, ensuring that it knows what is necessary.


Let's speak in biology terms:

    Evolution of learning:  There are multiple species in an ecosystem. One species feasts on the other, one species competes with the others for the same resources. Now, it is a constant arm's race between species thanks to evolution. Over the evolution period,  a structure evolved that allowed an organic species to be able to dynamically change its response to the surrounding's stimuli. No more, did a species have to wait for hundreds of generations to adapt its behaviour to a surrounding. Environment changes, ability to learn ensures an organism keeps up with the change.


    A neural network: A simple neural network is a line of neurons with an input neuron, and an output neuron that is connected to a muscle (a way to interact with the surroundings)

Fig 1.0: A basic neural network

    Learning involves: the change in the properties of connection between 2 or more neurons in the network. This is all basic knowledge, but what has me stumped is HOW do each of the neurons change connections to achive a desired result?

How does a dog learn tricks? How does a human learn to walk?
by practice. Each practice makes certain connections stronger and newer connections are formed. 
However, it seems that the intelligent beings also use feedbacks after a practice and somehow figure out what to adjust. And all this happens very fast.

Fig 1.1: a graph of accuracy vs time


This is the famous learning curve.

    So, do the neurons try changing each and every connections and keep the configuration that works out? Theoretically, that will be absolutely ineffecient. In higher intelligent organisms, not all neurons are tested. Only a select few neurons are tested using trial and error. 
    Basically, this points towards another learning algorithm layer on top of the basic neural network that governs the process of learning. Interestingly, the learning algorithm also learns ...to be continued







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