False memory research has been very popular over the last several years, in part because of its connection to one of the more contentious debates in cognitive science: the recovered memories debate. I remember attending a poster session at a conference a couple years ago, and an entire room was filled with posters on false memory experiments. The vast majority of the experiments on false memory aren't the least bit interesting, because they tell us very little about memory, or anything else for that matter, and they all use variants of the same two experimental paradigms. As you can probably imagine, reading about minute variations on the same experiment over and over again can become pretty tedious. But once and a while, an interesting variant does come around. I read about one today, so I thought I'd post about it.
First, how are false memory experiments done? As I said, there are two commonly used false-memory paradigms, the less popular of which is called the postevent misinformation paradigm. Experiments using this paradigm involve showing participants an event (usually in a video), and then giving participants false information about the event. After a delay, participants are asked to describe what they remember about the event. Often, participants mistakenly include the false information in their descriptions of the events.
In the more popular paradigm, usually called the Deese-Roediger-McDermott paradigm (DRM)1, participants are presented with a list of words all of which are related to a single concept that is not presented. For example, the words in the following list are all related to the concept DOCTOR2:
After reading the original list, participants are presented with a second list of words, some of which come from the original (list words), some of which were not on the original list and are not related to the concept associated with the list (foils), and also the word for the associated concept (critical words). Participants are asked to indicate which words were on the original list. In most experiments, participants will mistakenly remember having seen the critical word on the original list.
Now on to the experiment I read today. An interesting question for those of us who study concepts, memory, or language, is how do bilinguals represent and retrieve concepts shared by their two languages? It might be tempting to believe that the concepts are represented in a language specific way. Under this view, when a Spanish-English bilingual individual is speaking Spanish, she will retrieve the concepts about which she's speaking in a Spanish-specific format. This view fits nicely with the experience that many bilinguals have of thinking in the language they're using at the moment (and might explain research showing personality differences dependent on the current language in bilinguals). However, there is some evidence that bilinguals actually have language-independent conceptual representations. For example, semantic priming, which involves priming the meaning of a word rather than its lexical form (the DRM paradigm is essentially a semantic priming paradigm), can occur across languages (i.e., the primes are given in one language, and the target word in another)3, while priming in lexical decision tasks (deciding whether a word-string is a word) does not occur across languages4. Combined, these results indicate that bilingual individuals store lexical information (information about the forms of words) in language-specific formats, but store the meanings of words in language-independent formats.
In order to provide further evidence for this hypothesis, Sahlin et al. (2005; reference in footnote 2) used the DRM paradigm to determine whether false memories occur across languages. Past research using the postevent misinformation paradigm has shown that false memories can occur when the misinformation is given in one language, and the memory test in another4, but this doesn't tell us much about conceptual representations in bilinguals. However, because the DRM paradigm is essentially involves semantic priming of the critical words, if participants show false memories in this paradigm, it will provide evidence for language-specific conceptual representations.
So, Sahlin et al. developed 24 lists, each containing 15 words associated with a single concept, and divided them into two sets of 12 lists. In each set, six of the lists were presented orally in English, and six in Spanish, to Spanish-English bilingual participants in the learning phase. The participants were then given 5 recognition trials, each of which involved the same 96 words. The 96 words were drawn from the two list sets, with 3 from each of the 24 lists, along with critical words from all 24 lists. Since each participant heard only one list set, the test lists consisted of 36 list words, 12 critical words, and 48 foils (the list and critical words from the list set they had not heard) for each participant. Of each type of word (list, critical, and foil), half were presented in the same language in which they had originally been heard, and half were presented in the other language.
The results are presented in the table below (from Sahlin et al., Table 1, p. 1417) The data in the table is the proportion of each type of word that participants indicated they had heard in the original list. There are a few things to notice in the table. The first is that there is a big difference in accuracy between words that were presented in the same language in the learning and recall lists (English-English and Spanish-Spanish in the table) and words that were presented in different languages in the learning and recall lists (English-Spanish and Spanish-English). Participants were much more accurate when recognizing list words, and were much more likely to mistakenly recognize critical words, for words presented in the same language. The authors don't really discuss this difference, but if nothing else, it shows that recognizing words in one language when they were presented in another is really difficult. However, regardless of whether the words were presented in the same or different languages, participants mistakenly recognized the critical words as often or more often than they recognize list words, thus indicating that false memories can occur across languages in bilinguals. The experiment therefore provides good evidence for language-independent conceptual representations in bilinguals.
The other thing to notice is that in all conditions, accuracy for critical words increased (i.e., correctly indicating that the critical words were not on the original list) with each recognition trial. For the same language conditions, accuracy also increased for the list words over the recognition trials. These results are pretty common in experiments using the DRM paradigm, and are usually taken to indicate that participants rely on conceptual information in the first few recognition trials, but eventually forget that information and rely primarily on lexical information in later trials. Sahlin et al. therefore argue that the increase in accuracy for critical words in the different language conditions indicates that bilinguals switched from relying on conceptual information to relying on lexical information even when the words were presented in different languages. However, I think their data actually indicates something slightly different, and perhaps more interesting. While accuracy does increase over the five recall trials for critical words in the different language conditions, it dramatically decreases for list words over the five trials. I interpret this as an indication that as the availability of conceptual information decreased over the trials, participants had a difficult time recognizing list words, and an easier time rejecting critical words. This would imply that recognizing words learned in one language and then presented in another relies heavily on language-independent conceptual information.
1 Roediger, H. L., III, & McDermott, K. B. (1995). Creating false memories: Remembering words not presented in lists. Journal of Experimental Psychology: Learning, Memory, & Cognition, 21, 803-814 and Deese, J. (1959). On the prediction of occurrence of particular verbal intrusions in immediate recall. Journal of Experimental Psychology, 58, 17-22.
2From Sahlin, B.H., Harding, M.G., & Seamon, J.G. (2005). When do false memories cross language boundaries in English-Spanish bilinguals? Memory and Cognition, 33(8), 1414-1421.
3Chen, H.-C., & Ng, M.-L. (1989). Semantic facilitation and translation priming effects in Chinese-English bilinguals. Memory and Cognition, 17, 454-462.
4Gerard, L. D., & Scarborough, D. L. (1989). Language-specific lexical access of homographs by bilinguals. Journal of Experimental Psychology: Learning, Memory, & Cognition, 15, 305-315.
5Shaw, J. S., III, Garcia, L. A., & Robles, B. E. (1997). Cross-language postevent misinformation effects in Spanish-English bilingual witnesses. Journal of Applied Psychology, 82, 889-899.