Smith, S.M., Tindell, D.R., Sifonis, C.M., & Wilkenfeld, M.J. (2000). Category structure and created memories. Memory & Cognition, 28, 386-395.

Cued recall of categorized lists was used to examine the effects of category structure on the creation of false memories. The guiding effect of category or other conceptual knowledge can help the retrieval process by providing facilitative cures, but the same guiding knowledge can also lead to systematic errors. In this study, false recall was examined as a function of the category knowledge used to guide the recall process. Categories tend to have graded structures. Typical category members have been seen to be recalled better than atypical items from categorized lists that participants had studied. The primary interest in this study was the effects of category knowledge on the creation of false memories. Typical category members should be falsely recalled more frequently than atypical items because they should be more easily accessed during recall.

Another measure of item accessibility is output dominance, the frequency with which an item is listed as an instance of a category in a category production norm study. The role of output dominance was examined in the present studies. It has been shown that exemplars with the highest output dominance for a given category are the ones most likely to influence the form of the new ideas that people create from that category in a task of imagination.

Here, the efficacy of the categorized false recall methodology for evoking false recall of the targeted nonpresented items, using an immediate or a delayed category cued recall test, was examined. Experiment 1 tested the hypothesis that if common members of categories were omitted from categorized word lists, then false recall of the common category members would occur. The effect of a brief delay on false recall of nonpresented category members was also tested.

-Nine categorized lists were constructed from Rosch’s semantic category study. Each list corresponded to a different category, and each contained 15 items from a category with the most typical member omitted from each list and the next 15 most typical exemplars were included on each list.

-Participants viewed all nine categorized lists, with a recall test either immediately after each list or with recall tests delayed until all nine lists had been studied.

-There was a significant effect of type of response (correct list words were more likely to be recalled than were critical intrusions, TABLE 1).

-A significant interaction was found of delay with type of response (more critical intrusions were found in the delayed test than on the immediate test, whereas fewer correct answers occurred on the delayed test than on the immediate test).

-This experiment demonstrated the effectiveness of the category cued recall paradigm in evoking critical intrusions. They found greater numbers of critical intrusions when the recall test was immediate. The output dominance of nonpresented category members was found to be strongly correlated with the frequency of their occurrence as intrusions.

Here, a broader range of dominance of the critical omitted items was examined. The categorized target lists were more spread out to include high, medium, and low output dominance items. There were 2 parts to the experiment:

The primary interest was the relation between frequency of false recall of an item and the goodness of that item as a category member, as measured by typicality ratings or output dominance measures.

-After rank ordering the 30 exemplars of each category according to output dominance, alternate items were assigned creating two different study lists for each category that were approximately equal to each other in output dominance

-Essentially the same procedure was used in this experiment as in Experiment 1. There were 10 lists studied and recalled. Confidence scores were also given for each word after they were first studied and recalled. Scores ranged from a complete guess (1) to absolutely certain it was on the list (10).

-Items higher in typicality and output dominance were both falsely and correctly recalled more than items in lower typicality and output dominance, and the correlation between output dominance and recall was somewhat stronger than the correlation between typicality and recall.

-Items with a high output dominance were more likely to be recalled than items with a low output dominance.

-The incremental contribution of typicality was significant in predicting proportion correct as was the incremental contribution of output dominance.

-Items with a high output dominance were more likely to be recalled than items with a low output dominance.

-Confidence was higher for items low in typicality and low in output dominance.

The results suggest that false recall is related more to accessibility, as measured by output dominance, rather than to distinctiveness, as measured by typicality ratings. Output dominance was also found to be a better predictor of accurate recall. The results suggest that both false and accurate recall are strongly determined by the retrieval fluency of items, but not by their distinctiveness.

This experiment sought experimental evidence that false recall of items is more difficult to evoke the lower the output dominance of the items. A priming technique was used for evoking false recall. The effects of priming and output dominance were examined in Experiment 3. For each categorized list, a prime corresponded to a nonpresented high output dominance member, a nonpresented medium output dominance member, a nonpresented low output dominance member, or a nonmember (no prime) of the category.

-8 categorized lists were modified for use. There were 3 critical items identified for each category.

-4 different priming lists of 18 words were constructed.

-The priming procedure involved an incidental learning task in which the participants rated the pleasantness of words. The remaining procedure was the same as described in Experiment 1, except that all of the eight cued recall tests were delayed.

-There was a significant effect for type of list and for type of response.

-The effect of type of response was significant for the low dominance and medium dominance primed lists.

-The correct recall rate was no different from the critical intrusion rate for primed high dominance items.

-There were significant effects of output dominance and priming.

-There was no effect of output dominance on confidence in intrusions.

These results replicate and extend the findings of the first 2 experiments of the present study. The higher the output dominance of the category member, the greater the proportion of critical intrusion observed for that item.

The present experiments show that nonpresented category members are often falsely recalled on category cued recall tests and that delaying recall tests and priming critical items increase the frequency of such false or created memories. The results show that output dominance is a powerful predictor of both accurate and created memories and may account for some reported recall test results that have been attributed to typicality.