What characteristic differentiates an echoic from other verbal operants?

The distinguishing characteristic of an echoic verbal operant is that it relies on imitation of auditory stimuli. An echoic response occurs when an individual repeats what they have heard, effectively mimicking the sounds, words, or phrases that were presented to them. This form of verbal behavior is unique because it specifically requires the listener to hear and replicate the auditory input, rather than generating responses based on questions, visual cues, or original thoughts.

In contrast, the other options highlight aspects of verbal behavior that are not indicative of echoics. For example, answering questions represents a different verbal operant known as a "tact" or "intraverbal," depending on the context. Visual stimuli are not directly involved in echoic responses, which are strictly auditory. Original thought formation is also unrelated since echoic responses focus on reproduction rather than invention or creativity. Hence, the reliance on auditory imitation is what distinctly defines echoics among verbal operants.