Optimizing the mnemonic similarity task for efficient, widespread use

Introduction: The Mnemonic Similarity Task (MST) has become a popular test
of memory and, in particular, of hippocampal function. It has been heavily
used in research settings and is currently included as an alternate
outcome measure in a number of clinical trials. However, as it typically
requires ~15 min to administer and benefits substantially from an
experienced test administrator to ensure the instructions are
well-understood, its use in trials and in other settings is somewhat
restricted. Several different variants of the MST are in common use that
alter the task format (study-test vs. continuous) and the response prompt
given to participants (old/similar/new vs. old/new). Methods: In eight
online experiments, we sought to address three main goals: (1) To
determine whether a robust version of the task could be created that could
be conducted in half the traditional time; (2) To determine whether the
test format or response prompt choice significantly impacted the MST’s
results; and (3) To determine how robust the MST is to repeat testing. In
Experiments 1–7, participants received both the traditional and alternate
forms of the MST to determine how well the alternate version captured the
traditional task’s performance. In Experiment 8, participants were given
the MST four times over approximately 4 weeks. Results: In Experiments
1–7, we found that the test format had no effect on the reliability of the
MST, but that shifting to the two-choice response format significantly
reduced its ability to reflect the traditional MST’s score. We also found
that the full running time could be cut in half or less without an
appreciable reduction in reliability. We confirmed the efficacy of this
reduced task in older adults as well. Here, and in Experiment 8, we found
that while there often are no effects of repeat-testing, small effects are
possible, but appear limited to the initial testing session. Discussion:
The optimized version of the task developed here (oMST) is freely
available for web-based experiment delivery and provides an accurate
estimate of the same memory ability as the classic MST in less than half
the time.

引言：关联记忆相似性任务（Mnemonic Similarity Task, MST）现已成为记忆功能，尤其是海马体功能检测的经典范式，被广泛应用于各类研究场景，目前已作为替代结局指标纳入多项临床试验。不过，该任务通常需耗时约15分钟完成，且对施测者的专业经验有较高要求，以确保参与者充分理解指导语，因此在临床试验及其他场景中的应用受到一定限制。当前主流的MST存在多种变体，这些变体在任务形式（学习-测试范式vs. 连续范式）以及对参与者的反应提示（“旧识/相似/新异”vs. “旧识/新异”）上存在差异。

方法：本研究通过八项线上实验，旨在达成三个核心研究目标：（1）开发一款可靠的精简版任务，使其施测时长仅为传统版本的一半；（2）探究任务形式或反应提示方式的选择是否会对MST的测试结果产生显著影响；（3）评估MST在重复施测情境下的稳定性。在实验1至7中，参与者同时完成传统MST与变体MST，以验证变体版本能否有效复刻传统任务的测试表现。在实验8中，参与者在约4周的周期内完成四次MST测试。

结果：在实验1至7中，我们发现任务形式对MST的信度无显著影响，但将反应模式切换为二选一格式（即仅提示“旧识/新异”）会显著削弱其与传统MST得分的对应性。此外，我们证实可将任务总时长压缩至原有的一半甚至更短，且不会导致信度出现明显下降。我们还在老年群体中验证了该精简任务的有效性。在本部分结果及实验8中，我们发现尽管重复施测通常不会产生显著影响，但仍可能存在小幅效应，且这类效应似乎仅局限于首次施测阶段。

讨论：本研究开发的优化版关联记忆相似性任务（optimized Mnemonic Similarity Task, oMST）可免费用于线上实验施测，其能在耗时不足传统经典MST一半的前提下，精准评估与经典MST一致的记忆能力。