How is recognition memory affected by experimental blocking?


It is commonplace in episodic memory research to probe participants’ memory of a particular event multiple times throughout an experiment. It is usually assumed that participants’ memory for an event, once formed, does not change throughout the course of an experiment, and therefore that the time in which the memory is probed does not affect responding. However, there is a possibility that participants’ memory for an event actually changes throughout the course of an experiment (e.g., due to forgetting) and therefore, it may be problematic to assume that responses about a particular event at different times actually reflect the same memories.

Research Questions / Hypotheses

Our aim was to determine whether participants were consistent with their responses when probed about a particular memory at different points in the experiment. It was hypothesized that for the vast majority of learned events, participants would be consistent in their responses, regardless of the time in which their memory was probed.


A total of 61 REP participants completed the study.


Participants completed 6 cycles of a memory task, with each involving a study phase and test phase. In the study phase, participants were presented with several words on a computer screen, one at a time. During the test phase, participants were first presented with each of the words from the study phase and an equal amount of words that had not been seen before. They were asked to determine whether each of these words was a “NEW” word or an “OLD” word. Following this, participants were presented with each of the words shown in the study phase again and were asked whether they could honestly recall seeing each word initially. In half of the cycle, this “remember” test would precede the aforementioned “recognition” test.


It was found that for both experimental conditions (i.e., having the recognition test first, or the remember test first), participants were remarkably inconsistent with their responses about particular items from one point in the experiment to the next. Roughly half the time a participant responded with having remembered an item, they would later go on to identify the item as a “NEW” word. Similarly, roughly half the time an item was identified as “OLD”, it would later go on to be labelled as “not remembered”.


The results of this experiment suggest that participants’ memory of an event is not the same from one point in an experiment to another. Although the reasons for this phenomenon remain unclear, it is clear that future experiments in episodic memory should not probe participants about their memory for an event at different intervals while expecting consistency; instead, it would be preferable for participants to only ever answer questions about a particular event at the same time during the experiment. The results from this study will be written up as a journal article for publication, and will be presented at various conferences on psychological research.