And since this type of relational responding can be arbitrarily applied to any pair of stimuli, it is a generalized operant. It was taught via multiple exemplar training. This kind of training could allow humans to make relational responses based on contextual cues, rather than the physical properties of the stimuli. With enough training, contextual cues can predict reinforcement for making a particular type of relational response to the stimuli.
In the real world, of course, this type of training typically occurs in many different settings for many different types of relational responses. Many different contextual cues are used, and many different types of stimuli are related.