Final answer:
The primacy effect is caused by the increased opportunity to rehearse items at the beginning of a list, facilitating their transfer into long-term memory, which aligns with research on memory and recall.
Step-by-step explanation:
The cause of the primacy effect in memory is attributed to items heard at the beginning of a list having more opportunity to be rehearsed and thus transferred into long-term memory. This can be explained by the fact that the items at the beginning of the list are presented first and therefore have the most time to be mentally reviewed by the individual, allowing for stronger memory consolidation. Additionally, words at the beginning of the list are not subject to proactive interference, which makes them easier to recall compared to items from the middle of the list.
Memory research by Craik & Watkins (1973) emphasizes the role of rehearsal in short-term memory. Hence, the correct answer to the student's question is option 2) Words at the beginning of the list have the most opportunity to be rehearsed. This fits with the key concept of how rehearsal tends to enhance memory retention and relates to the primacy effect as a phenomenon observed in various studies on memory and recall.