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Bilingual false recollection: An EEG study
Brain and Language 99 (2006) 8–219 www.elsevier.com/locate/b&l
Bilingual false recollection: An EEG study Antonio Ibanez Molina, I. Fan Su, Charlotte Knight, Robyn Holliday, Brendan S. Weekes
*
University of Sussex, UK Accepted 6 July 2006
Introduction False recollection in the Deese-Roediger-McDermott (DRM) paradigm describes the phenomenon of remembering critical words, e.g., SLEEP that are thematically related to a list of study words, e.g., BED, REST, AWAKE. Different theoretical accounts of false recollection generate alternative predictions about the false memory effect. Activation monitoring theory (AMT) (Roediger & McDermott, 1999) assumes that false recollection of critical words results from failure to monitor the source of activation, which is the same process that is used to correctly identify studied words and thus support veridical recollection. Fuzzy Trace Theory (FTT) (Brainerd & Reyna, 2002) assumes that false memories arise because participants automatically infer the theme or meaning of studied words but confuse words presented at test with nonpresented items that are representative of that theme and veridical recollection depends on verbatim memory. The difference between these accounts is FTT allows for dissociable memory traces and AMT does not. ERP studies investigating false recollection report little difference in indices for true and false recollection (Duzel, Yonelinas, Mangun, Heinze, & Tulving, 1997) although Miller, Baratta, Wynveen, and Rosenfeld (2001) reported a shorter P300 latency for false recollection and Fabiani, Stadler, and Wessels (2000) reported less left lateralisation for critical words. Other studies, however, report late negativity in false recollection that is localised to the frontal lobes (Curran, Schacter, Johnson, & Spinks, 2001; Johnson, Kounios, & Nolde, 1996, 1997). No study has examined false recollection in bilingual speakers using EEG. We know bilingual speakers are slower to access the semantic representations of words presented in their second language (L2) although this effect diminishes with proficiency in L2 (Kroll & Stewart, 1994). It is also known that Spanish–English bilingual speakers perform recognition tasks in L2 that rely on verbatim memory as well as and in some cases better than they perform the same tasks in L1 (Durgunoglu & Roediger, 1987). One prediction derived from FTT is that bilingual speakers will show reduced gist based memory for words presented in L2. By contrast, according to AMT there is no reason to assume that EEG signals for false and veridical memory will differ in bilingual speakers. Behavioural data suggests the false memory effect for Spanish–English bilingual speakers is smaller in L2 than L1 and veridical recollection is comparable (Anastasi, Rhodes, Marquez, & Vellino, 2005). We predicted that false recollection and veridical recollection in bilingual speakers would reveal a different pattern of EEG signals. *
Corresponding author. Fax: +44 1273 678611. E-mail address: [email protected] (B.S. Weekes).
doi:10.1016/j.bandl.2006.06.099
Specifically, we expected different patterns in late negativity signals on critical and studied word trials as found by Curran et al. (2001). Subjects and methods Fifteen native Spanish speakers were tested all undergraduates in Sussex studying in English. A within participants design was used with Recognition Type (Target words, Critical Distracters, Unrelated Distracters) as the independent variable. Distracters refer to words not studied but presented at test with critical distracters strong associates of study words and unrelated distracters not associated to study words. In the study phase, stimuli were presented in nine blocks with presentation order counterbalanced. Participants were instructed to remember words in the study lists. Each condition had 36 word lists presented in one of three orders with all participants studying all word lists. The presentation rate was one word every 2 s followed by a fixation cross for 300 ms. Participants were prompted to blink 1 s after each trial. After study, instructions were displayed for the distracter task. This involved counting backwards in twos aloud from 200 for 1 min. Instructions were then displayed for the recognition test. Thirty-nine words were presented for 2 s followed by a fixation cross for 300 ms and a question mark. Participants pressed yes to words seen at study and no to words that had not been on the study list. EEG was recorded from 28 sites using electrodes mounted in a elastic Quikcap (NeuroScan) continuously sampled at AD rate 1000 Hz/channel with references on left and right mastoids. The vertical electrooculagram (EOG) was recorded with electrodes above and below the left eye. Inter-electrode impedance was maintained below 5 kX. EEG and EOG were amplified using a 1–40 Hz band-pass filter. Trials with EOG artefacts (mean EOG voltage >±150 lV) were excluded from averaging. Results and conclusions Voltage change during false recollection (i.e., yes responses to critical distracters) and during veridical recollection (i.e., yes responses to studied words) was calculated. Results from selected electrodes are summarised in Fig. 1. ANOVA on the behavioural data found a significant effect of recognition type F (3, 14) = 110.98, p < .01, false recollection of critical distracters was less likely than recollection of target words and more likely than recollection of unrelated distracters (p’s < .01). There was also a correlation between proficiency in L2 and false recollection r = .54. Inspection of Fig. 1 shows a divergence in waveform amplitude that is greater than 1.5 SD between false and veridical trials in the epoch between 600 and 700 ms for Fz, Cz and CPz. Note also that the N400 at Fz, Cz and
Abstracts / Brain and Language 99 (2006) 8–219
181
Subject: EEGfile: GrandCriticalYes.avg Recorded : 14:44:11 08-Nov-2005 Rate - 1000 Hz,HPF - 0.05 Hz,LPF - 100 Hz, Notch - off
Neuroscan SCAN 4.3 Printed : 10:50:33 13-Dec-2005
*GrandCriticalYes.avg GrandTargetYes.avg
FPz
-12.5 -10.0 -7.5 -5.0 -2.5 µV 0.0 2.5 5.0 7.5 10.0 12.5 -150.0
Electrode: FPZ
100.0
350.0
600.0
850.0 ms
1100.0
1350.0
Subject: EEG file: GrandCriticalYes.avg Recorded : 14:44:11 08-Nov-2005 Rate - 1000 Hz, HPF - 0.05 Hz, LPF - 100 Hz, Notch - off
1600.0 Neuroscan SCAN 4.3 Printed : 10:51:33 13-Dec-2005
*GrandCriticalYes.avg GrandTargetYes.avg
Cz
-12.5 -10.0 -7.5 -5.0 -2.5 µV 0.0 2.5 5.0 7.5 10.0 12.5 -150.0
Electrode: CZ
100.0
350.0
600.0
850.0 ms
1100.0
1350.0
Subject: EEG file: GrandCriticalYes.avg Recorded : 14:44:11 08-Nov-2005 Rate - 1000 Hz, HPF - 0.05 Hz, LPF - 100 Hz, Notch - off
1600.0 Neuroscan SCAN 4.3 Printed : 10:52:05 13-Dec-2005
*GrandCriticalYes.avg GrandTargetYes.avg
CP z
-12.5 -10.0 -7.5 -5.0 -2.5 µV 0.0 2.5 5.0 7.5 10.0 12.5 -150.0
Electrode: CPZ
100.0
350.0
600.0
850.0 1100.0 ms
1350.0
1600.0
Fig. 1. ERPs of selected electrodes on false recollection trials (green) and correct recollection trials (red). CPz occurred earlier on false recollection trials. At most other sites (e.g., Oz) there was no significant divergence at any epoch and no evidence of an N400. The results fully support the predictions of FTT (Brainerd & Reyna, 1999). FTT assumes that the false memory effect is due to gist based memory processing and that veridical recollection depends on verbatim and gist memory processing. The behavioural data show reduced gist based memory is reduced for words presented in L2
and of greater importance EEG signals for false and veridical recollection are dissociable. There was no support for AMT (Roediger & McDermott, 1999), which assumes that veridical and false recollection results from the success of source monitoring processes. If diminished source monitoring leads to more false memory then false recollection should exceed veridical recollection in bilingual speakers given that L2 is the less familiar language. There is no support for this expectation in the behavioural data.
182
Abstracts / Brain and Language 99 (2006) 8–219
Other studies have found an N400 component that is more negative for critical words in the window 300–600 ms using semantic lists (Johnson et al., 1996). Our results suggest that this component is useful for detecting false recollection of words in bilingual participants. Some authors (Curran et al., 2001; Johnson et al., 1996, 1997) attribute late ERP recognition effects to post-retrieval evaluation. These processes may be more necessary for bilingual speakers and more so in false recollection trials. An alternative view is that greater negative voltage change in the false recollection condition reflects activation of lexical associations that are not only conceptual and more broadly related by association. According to FTT, false memories arise in DRM because participants automatically infer thematic relationships between study words and confuse studied and critical words. For bilingual participants there is an additional burden of translation, which although not required by the task, may be automatic. The additional lexical-semantic associations that are necessarily used by bilingual participants makes recollection in L2 a more demanding task. This hypothesis is tested by comparison to monolingual participants performing the same task. Acknowledgment Supported by a Marie Curie Research Fellowship from the Research Directorates General of the European Commission. References Anastasi, J. S., Rhodes, M. G., Marquez, S., & Vellino, V. (2005). The incidence of false memories in native and non-native speakers. Memory, 13(8), 815–828.
Brainerd, C., & Reyna, V. (2002). Fuzzy trace theory and false memory. Current Directions in Psychological Science, 11(5), 164–169. Curran, T., Schacter, D. L., Johnson, M. K., & Spinks, R. (2001). Brain potentials reflect behavioral differences in true and false recognition. Journal of Cognitive Neuroscience, 13, 201–216. Durgunoglu, A. Y., & Roediger, H. L. (1987). Test differences in accessing bilingual memory. Journal of Memory and Language, 26(4), 377–391. Duzel, E., Yonelinas, A. P., Mangun, G. R., Heinze, H. J., & Tulving, E. (1997). Event-related brain potential correlates of two states of conscious awareness in memory. PNAS, 94(11), 5973–5978. Fabiani, M., Stadler, M. A., & Wessels, P. M. (2000). True but not false memories produce a sensory signature in human lateralized brain potentials. Journal of Cognitive Neuroscience, 12(6), 941–949. Johnson, M. K., Kounios, J., & Nolde, S. F. (1996). Electrophysiological brain activity and memory source monitoring. NeuroReport, 7, 2929–2932. Johnson, M. K., Nolde, S. F., Mather, M., Kounios, J., Schacter, D. L., & Curran, T. (1997). The similarity of brain activity associated with true and false recognition depends on test format. Psychological Science, 8, 250–257. Kroll, J., & Stewart, F. (1994). Category interference in translation and picture naming: evidence for asymmetric connections between bilingual memory representations. Journal of Memory and Language, 33, 149–174. Miller, A. R., Baratta, C., Wynveen, C., & Rosenfeld, J. P. (2001). P300 Latency not amplitude or topography distinguishes between true and false recognition. Journal of Experimental Psychology: Learning. Memory and Cognition, 2, 354–361. Roediger, H., & McDermott, K. (1999). False alarms and false memories. Psychological Review, 106, 406–410.
Bilingual false recollection: An EEG study Antonio Ibanez Molina, I. Fan Su, Charlotte Knight, Robyn Holliday, Brendan S. Weekes
*
University of Sussex, UK Accepted 6 July 2006
Introduction False recollection in the Deese-Roediger-McDermott (DRM) paradigm describes the phenomenon of remembering critical words, e.g., SLEEP that are thematically related to a list of study words, e.g., BED, REST, AWAKE. Different theoretical accounts of false recollection generate alternative predictions about the false memory effect. Activation monitoring theory (AMT) (Roediger & McDermott, 1999) assumes that false recollection of critical words results from failure to monitor the source of activation, which is the same process that is used to correctly identify studied words and thus support veridical recollection. Fuzzy Trace Theory (FTT) (Brainerd & Reyna, 2002) assumes that false memories arise because participants automatically infer the theme or meaning of studied words but confuse words presented at test with nonpresented items that are representative of that theme and veridical recollection depends on verbatim memory. The difference between these accounts is FTT allows for dissociable memory traces and AMT does not. ERP studies investigating false recollection report little difference in indices for true and false recollection (Duzel, Yonelinas, Mangun, Heinze, & Tulving, 1997) although Miller, Baratta, Wynveen, and Rosenfeld (2001) reported a shorter P300 latency for false recollection and Fabiani, Stadler, and Wessels (2000) reported less left lateralisation for critical words. Other studies, however, report late negativity in false recollection that is localised to the frontal lobes (Curran, Schacter, Johnson, & Spinks, 2001; Johnson, Kounios, & Nolde, 1996, 1997). No study has examined false recollection in bilingual speakers using EEG. We know bilingual speakers are slower to access the semantic representations of words presented in their second language (L2) although this effect diminishes with proficiency in L2 (Kroll & Stewart, 1994). It is also known that Spanish–English bilingual speakers perform recognition tasks in L2 that rely on verbatim memory as well as and in some cases better than they perform the same tasks in L1 (Durgunoglu & Roediger, 1987). One prediction derived from FTT is that bilingual speakers will show reduced gist based memory for words presented in L2. By contrast, according to AMT there is no reason to assume that EEG signals for false and veridical memory will differ in bilingual speakers. Behavioural data suggests the false memory effect for Spanish–English bilingual speakers is smaller in L2 than L1 and veridical recollection is comparable (Anastasi, Rhodes, Marquez, & Vellino, 2005). We predicted that false recollection and veridical recollection in bilingual speakers would reveal a different pattern of EEG signals. *
Corresponding author. Fax: +44 1273 678611. E-mail address: [email protected] (B.S. Weekes).
doi:10.1016/j.bandl.2006.06.099
Specifically, we expected different patterns in late negativity signals on critical and studied word trials as found by Curran et al. (2001). Subjects and methods Fifteen native Spanish speakers were tested all undergraduates in Sussex studying in English. A within participants design was used with Recognition Type (Target words, Critical Distracters, Unrelated Distracters) as the independent variable. Distracters refer to words not studied but presented at test with critical distracters strong associates of study words and unrelated distracters not associated to study words. In the study phase, stimuli were presented in nine blocks with presentation order counterbalanced. Participants were instructed to remember words in the study lists. Each condition had 36 word lists presented in one of three orders with all participants studying all word lists. The presentation rate was one word every 2 s followed by a fixation cross for 300 ms. Participants were prompted to blink 1 s after each trial. After study, instructions were displayed for the distracter task. This involved counting backwards in twos aloud from 200 for 1 min. Instructions were then displayed for the recognition test. Thirty-nine words were presented for 2 s followed by a fixation cross for 300 ms and a question mark. Participants pressed yes to words seen at study and no to words that had not been on the study list. EEG was recorded from 28 sites using electrodes mounted in a elastic Quikcap (NeuroScan) continuously sampled at AD rate 1000 Hz/channel with references on left and right mastoids. The vertical electrooculagram (EOG) was recorded with electrodes above and below the left eye. Inter-electrode impedance was maintained below 5 kX. EEG and EOG were amplified using a 1–40 Hz band-pass filter. Trials with EOG artefacts (mean EOG voltage >±150 lV) were excluded from averaging. Results and conclusions Voltage change during false recollection (i.e., yes responses to critical distracters) and during veridical recollection (i.e., yes responses to studied words) was calculated. Results from selected electrodes are summarised in Fig. 1. ANOVA on the behavioural data found a significant effect of recognition type F (3, 14) = 110.98, p < .01, false recollection of critical distracters was less likely than recollection of target words and more likely than recollection of unrelated distracters (p’s < .01). There was also a correlation between proficiency in L2 and false recollection r = .54. Inspection of Fig. 1 shows a divergence in waveform amplitude that is greater than 1.5 SD between false and veridical trials in the epoch between 600 and 700 ms for Fz, Cz and CPz. Note also that the N400 at Fz, Cz and
Abstracts / Brain and Language 99 (2006) 8–219
181
Subject: EEGfile: GrandCriticalYes.avg Recorded : 14:44:11 08-Nov-2005 Rate - 1000 Hz,HPF - 0.05 Hz,LPF - 100 Hz, Notch - off
Neuroscan SCAN 4.3 Printed : 10:50:33 13-Dec-2005
*GrandCriticalYes.avg GrandTargetYes.avg
FPz
-12.5 -10.0 -7.5 -5.0 -2.5 µV 0.0 2.5 5.0 7.5 10.0 12.5 -150.0
Electrode: FPZ
100.0
350.0
600.0
850.0 ms
1100.0
1350.0
Subject: EEG file: GrandCriticalYes.avg Recorded : 14:44:11 08-Nov-2005 Rate - 1000 Hz, HPF - 0.05 Hz, LPF - 100 Hz, Notch - off
1600.0 Neuroscan SCAN 4.3 Printed : 10:51:33 13-Dec-2005
*GrandCriticalYes.avg GrandTargetYes.avg
Cz
-12.5 -10.0 -7.5 -5.0 -2.5 µV 0.0 2.5 5.0 7.5 10.0 12.5 -150.0
Electrode: CZ
100.0
350.0
600.0
850.0 ms
1100.0
1350.0
Subject: EEG file: GrandCriticalYes.avg Recorded : 14:44:11 08-Nov-2005 Rate - 1000 Hz, HPF - 0.05 Hz, LPF - 100 Hz, Notch - off
1600.0 Neuroscan SCAN 4.3 Printed : 10:52:05 13-Dec-2005
*GrandCriticalYes.avg GrandTargetYes.avg
CP z
-12.5 -10.0 -7.5 -5.0 -2.5 µV 0.0 2.5 5.0 7.5 10.0 12.5 -150.0
Electrode: CPZ
100.0
350.0
600.0
850.0 1100.0 ms
1350.0
1600.0
Fig. 1. ERPs of selected electrodes on false recollection trials (green) and correct recollection trials (red). CPz occurred earlier on false recollection trials. At most other sites (e.g., Oz) there was no significant divergence at any epoch and no evidence of an N400. The results fully support the predictions of FTT (Brainerd & Reyna, 1999). FTT assumes that the false memory effect is due to gist based memory processing and that veridical recollection depends on verbatim and gist memory processing. The behavioural data show reduced gist based memory is reduced for words presented in L2
and of greater importance EEG signals for false and veridical recollection are dissociable. There was no support for AMT (Roediger & McDermott, 1999), which assumes that veridical and false recollection results from the success of source monitoring processes. If diminished source monitoring leads to more false memory then false recollection should exceed veridical recollection in bilingual speakers given that L2 is the less familiar language. There is no support for this expectation in the behavioural data.
182
Abstracts / Brain and Language 99 (2006) 8–219
Other studies have found an N400 component that is more negative for critical words in the window 300–600 ms using semantic lists (Johnson et al., 1996). Our results suggest that this component is useful for detecting false recollection of words in bilingual participants. Some authors (Curran et al., 2001; Johnson et al., 1996, 1997) attribute late ERP recognition effects to post-retrieval evaluation. These processes may be more necessary for bilingual speakers and more so in false recollection trials. An alternative view is that greater negative voltage change in the false recollection condition reflects activation of lexical associations that are not only conceptual and more broadly related by association. According to FTT, false memories arise in DRM because participants automatically infer thematic relationships between study words and confuse studied and critical words. For bilingual participants there is an additional burden of translation, which although not required by the task, may be automatic. The additional lexical-semantic associations that are necessarily used by bilingual participants makes recollection in L2 a more demanding task. This hypothesis is tested by comparison to monolingual participants performing the same task. Acknowledgment Supported by a Marie Curie Research Fellowship from the Research Directorates General of the European Commission. References Anastasi, J. S., Rhodes, M. G., Marquez, S., & Vellino, V. (2005). The incidence of false memories in native and non-native speakers. Memory, 13(8), 815–828.
Brainerd, C., & Reyna, V. (2002). Fuzzy trace theory and false memory. Current Directions in Psychological Science, 11(5), 164–169. Curran, T., Schacter, D. L., Johnson, M. K., & Spinks, R. (2001). Brain potentials reflect behavioral differences in true and false recognition. Journal of Cognitive Neuroscience, 13, 201–216. Durgunoglu, A. Y., & Roediger, H. L. (1987). Test differences in accessing bilingual memory. Journal of Memory and Language, 26(4), 377–391. Duzel, E., Yonelinas, A. P., Mangun, G. R., Heinze, H. J., & Tulving, E. (1997). Event-related brain potential correlates of two states of conscious awareness in memory. PNAS, 94(11), 5973–5978. Fabiani, M., Stadler, M. A., & Wessels, P. M. (2000). True but not false memories produce a sensory signature in human lateralized brain potentials. Journal of Cognitive Neuroscience, 12(6), 941–949. Johnson, M. K., Kounios, J., & Nolde, S. F. (1996). Electrophysiological brain activity and memory source monitoring. NeuroReport, 7, 2929–2932. Johnson, M. K., Nolde, S. F., Mather, M., Kounios, J., Schacter, D. L., & Curran, T. (1997). The similarity of brain activity associated with true and false recognition depends on test format. Psychological Science, 8, 250–257. Kroll, J., & Stewart, F. (1994). Category interference in translation and picture naming: evidence for asymmetric connections between bilingual memory representations. Journal of Memory and Language, 33, 149–174. Miller, A. R., Baratta, C., Wynveen, C., & Rosenfeld, J. P. (2001). P300 Latency not amplitude or topography distinguishes between true and false recognition. Journal of Experimental Psychology: Learning. Memory and Cognition, 2, 354–361. Roediger, H., & McDermott, K. (1999). False alarms and false memories. Psychological Review, 106, 406–410.