视觉长时记忆激活度对促进视觉短时记忆的影响

短时记忆与长时记忆的关系是记忆领域研究的重要内容。基于此, 研究者们就视觉长时记忆是否能促进视觉短时记忆的问题展开了大量研究, 但所得出的结论并不一致。通过不同程度的学习形成不同激活度的视觉长时记忆, 考察对几何图形的视觉长时记忆是否能对变化检测中的短时记忆起到促进作用。结果发现, 低激活水平的视觉长时记忆不能促进视觉短时记忆, 而事先存在且高度激活的视觉长时记忆对视觉短时记忆却具有促进作用; 同时, 随着视觉长时记忆激活水平的提高, 刺激间间隔的效应值也逐渐减小。本研究说明, 视觉长时记忆能否促进视觉短时记忆取决于视觉长时记忆的激活水平, 高激活的视觉长时记忆对阻止视觉短时记忆痕迹的迅速消退具有重要意义。

The Effects of Activation Levels of Visual Long-Term Memory on Visual Short-Term Memory

It is a fundamental question that whether visual short-term memory (VSTM) and visual long-term memory (VLTM) are two separate stores or two different states of the same representation. Previous researches focused on whether VSTM could be facilitated by VLTM, however, existing studies on this topic yielded conflicting results. Most neurophysiological or behavioral studies adopted faces as stimuli, and have arrived at the conclusion that VLTM could facilitate VSTM. It ought to be noted that in studies that found no facilitation, the exposure of the experimental materials was not sufficiently to activate VLTM. Therefore, it was hypothesized that only a highly activated VLTM could facilitate VSTM. The purpose of the present study was to investigate the effect of activation level of VLTM on facilitating VSTM within the change-detection paradigm. In Experiment 1, participants were instructed to memorize a study image including 6 geometric figures (6 random shape-color bindings from a pool of eight shapes and eight colors), and then after a random inter-stimulus interval (1, 1.5, or 3 s), either the same image or an image with one shape or color changed was presented, and participants were asked to judge whether they detected a change. In Experiment 2, a total of 8 geometric figures with fixed combinations of color and shape were used to substitute all the random combinations of experiment 1. The experimental procedure and design was identical to experiment 1. One hour after the experiment, participants were asked to participate in a post-experiment to examine whether the study stimuli were stored in VLTM. In Experiment 3, participants were asked to visually study the 8 figures in experiment 2 for a week (at least 10 min a day). Then, they took part in a pre-experiment (the same as the post-experiment in experiment 2) to test whether a highly activated VLTM was obtained. At last, the experimental procedure as described in Experiment 2 was performed. The results showed that although VLTM was formed in experiment 2, there was no significant increase in d' or K value of VSTM, indicating no facilitation of VLTM in this case. However, in experiment 3, VLTM was highly activated, and a better performance was observed as compared with experiment 1 and 2. In addition, the effect size of ISI decreased as the activation level of VLTM increased from experiment 1 to experiment 3. The results suggest that whether VLTM can facilitate VSTM is mainly depend on the activation level of VLTM, only a highly activated VLTM can facilitate VSTM, and can inhibit the rapid fading of VSTM traces. On this basis, we conclude that VSTM and VLTM are more likely to be two states of the same representation.