What are meaningless sets of two consonants with a vowel between them called?

The term that refers to meaningless sets of two consonants with a vowel between them is indeed "nonsense syllables." Nonsense syllables are often used in psychological research, particularly in studies related to memory and learning, as they allow researchers to control for prior knowledge and associations that might interfere with the learning process. By using combinations of consonants and vowels that do not form actual words, researchers can examine how people learn and remember information that lacks meaning.

Other terms like "random sequences," "abstract patterns," and "complex relations" do not specifically capture the essence of the structured nature of nonsense syllables, which have a defined phonetic format (CVC: consonant-vowel-consonant) but no semantic content. This distinction is crucial in the context of understanding how we process and retain information.