
200 Chapter 7 ConneCtionist Models
With the perceptron learning rule, the network is unable to determine
the scale by which weights have to be adjusted. The second perceptron
shown in Figure 7.8 does not know the actual inputs, as they are masked by
the first perceptron. Thus, it is difficult for the second perceptron to learn
correctly. Assigning a nonlinear threshold function (like a sigmoid function
instead of a bi-state on/off or 0/1) helps a bit in this situation. This leads to
the need for a multilayer
network, which is an important step in building
intelligent machines from neuronlike components. Figure 7.9 shows the ar-
chitecture ...