Adjust weights and bias to see how a single sigmoid neuron draws a linear decision boundary through the XOR input space.
Parameters
Weight A (wa)4.0
Weight B (wb)4.0
Bias (b)−2.0
Forward pass
ŷ = ...
P̂ = σ(ŷ)
(a=0, b=0) · true: 0
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(a=0, b=1) · true: 1
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(a=1, b=0) · true: 1
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(a=1, b=1) · true: 0
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Why can't one neuron solve XOR?
A single neuron draws one straight line. XOR requires two — no single linear boundary separates the classes correctly. Red border = misclassified point.