Informal learning is an unorganized form of learning with no precise set of objectives; the learning is unintentional and is perceived from surroundings and interactions. In the context of the essay, the fear of the dark occurs because of the inability to gauge potential danger due to lack of vision.
I was told not to go at night to the neighborhood ice cream parlor by my dad because there were some security issues due to darkness on the street but I did. My friend and I were walking down the street in the dim light and suddenly two men came and mugged a stranger who was walking just some miles away from us. He resisted and was harmed. We called for help and the robbers ran. I was scared and kept thanking that it was not us. This informal teaching has taught me over the period not to go in dark and vacant places and I have become extra cautious in such situations.
The fear of the dark can be acquired through classical conditioning "There is not and never has been any convincing evidence for unconscious, automatic mechanism in the conditioning of adult human beings”. (Brewer 1974, p.27) The dark street is the unconditioned stimulus (UCS) which is the environment accountable for the response. The unconditioned response (UCR) is caution which is the automatically occurring reaction brought about by the dark street.
The conditioned stimulus (CS) shows that dark streets can be risky; hence the conditioned response is fear, which is the aroused
References: Brewer, William F. (1974), “There is no convincing evidence for operant or classical condition in adult humans”, in Cognition and the Symbolic processes, eds. Walter B. “Delayed extinction attenuates conditioned fear renewal and spontaneous recovery in humans.” Huff, Nicole C.; Hernandez, Jose Alba; Blanding, Nineequa Q.; LaBar, Kevin S. Behavioral Neuroscience, Vol 123(4), Aug 2009