John G. Seamon

Remembering words not presented in lists: Can we avoid creating false memories?

Can subjects avoid creating false memories as outlined in Roediger and McDermott’s (1995) false recognition paradigm if they are forewarned about this memory illusion? We presented subjects with semantically related word lists, followed by a recognition test. The test was composed of studied words, semantically related nonstudied words (critical lures), and unrelated nonstudied words. One group of subjects was uninformed about the false recognition effect, a second group was urged to minimize all false alarms, and a third group was forewarned about falsely recognizing critical lures. Compared with the uninformed and cautious subjects, the forewarned subjects reduced their false alarm rate for critical lures, and they made remember and know judgments equally often for recognized studied words and critical lures. But forewarning did not eliminate the false recognition effect, as these subjects and those in the other groups made numerous false recognitions in this task.

Affective discrimination of stimuli that are not recognized: effects of shadowing, masking, and cerebral laterality

Based on his finding that subjects can show an affective preference to previously seen stimuli that they fail to recognize, Zajonc (1980) claimed that affective processing operates separately from cognitive processing. Over four experiments, we replicated and extended the finding that mere exposure to a briefly presented stimulus can increase positive affect through familiarity without enhancing the recognition of that stimulus. Among our findings, lateralized presentation of the irregular polygon stimuli showed that affect judgments were best for stimuli presented in the right visual field (left hemisphere), whereas recognition judgments were best for stimuli presented in the left visual field (right hemisphere). These effects were found only when the study stimuli were shown for 2 msec and were unmasked or for 5 msec and were pattern masked; when the stimuli were shown for 5 msec and were energy masked, target selection by affect or recognition was not greater than chance. These data, along with results from contingency probability analyses, indicate that affect and recognition judgments are different. Rather than viewing the difference between affect and recognition in terms of different features that might reside in the stimulus, the difference in judgments may reflect the manner in which a stimulus representation has been accessed. When viewed in terms of different retrieval processes that access different information, target selection by affect in the absence of recognition can be interpreted in terms of existing models of recognition memory.

Coding Strategies and Cerebral Laterality Effects

In a short-term recognition memory task, Ss were given relational imagery and rehearsal coding strategies in different sessions, with probes presented to the left or right cerebral hemisphere. Consistent with a model of separate processing systems for verbally and visually coded information, Ss yielded significantly faster response latencies for probes to the left hemisphere than the right when employing the rehearsal strategy, and significantly faster latencies for probes to the right hemisphere than the left when using the imagery code. This suggests that cerebral lateral@ effects are functionally related to coding strategies, and argues for the inclusion of imagery, or generated visual information, as part of the visual processing system. As such, generated visual information may be viewed as a coding alternative to verbal mediation. It is well-known that information can be represented or coded in different forms in memory. Conrad ( 1964) noted that Ss made acoustic confusions in a recall task, even though the original stimulus presentation was visual. The acoustic confusions suggest that the Ss recoded the stimuli from a visual to a verbal base prior to recall. Posner, Boies, Eichelman, and Taylor (1969) present data which are consistent with the hypothesis that Ss can generate a visual representation of an auditorily presented letter. Further, Bahrick and Boucher ( 1968) have demonstrated that object drawings may be visually or verbally coded in memory independently. Additional research has shown that stimulus (Tversky, 1969) and task (Frost, 1972) expectancy can influence the

Double dissociation of spatial and object visual memory: evidence from selective interference in intact human subjects

A functional dissociation of the spatial and object visual systems was produced by selective interference in intact young adults. Subjects were instructed to remember the location of a dot in a spatial memory test, and the form of an object memory test. As predicted by current notions of dissociable visual systems in the primate, spatial memory was selectively impaired by a movement discrimination spatial task, whereas object memory was selectively impaired by a color discrimination object task.

Creating False Memories of Words With or Without Recognition of List Items: Evidence for Nonconscious Processes

Subjects exposed to lists of semantically related words falsely remember nonstudied words that are associated with the list items (e.g., Deese, 1959; Roediger & McDermott, 1995). To determine if subjects would demonstrate this false memory effect if they were unable to recognize the list items, we presented lists of semantically related words with or without a concurrent memory load at rates of 2 s, 250 ms, or 20 ms per word (Experiment 1, between-subjects design) and 2 s or 20 ms per word (Experiment 2, within-subjects design). We found that the subjects falsely recognized semantically related nonstudied words in all conditions, even when they were unable to discriminate studied words from unrelated nonstudied words. Recognition of list items was unnecessary for the occurrence of the false memory effect. This finding suggests that this memory illusion can be based on the nonconscious activation of semantic concepts during list presentation.

Critical importance of exposure duration for affective discrimination of stimuli that are not recognized

Previous research has found that repeated exposure to briefly presented visual stimuli can increase the positive affect for the stimuli without enhancing their recognition. Subjects could discriminate target and distractor shapes by affective preference in the absence of recognition memory. This study examined this phenomenon as a function of stimulus exposure duration. Over exposure durations of 0, 2, 8, 12, 24, and 48 ms, the functions for affect and recognition judgments exhibited different temporal dynamics. Target selection by affect was possible at very brief exposures and was influenced little by increasing durations; target selection by recognition required longer stimulus exposures and improved with increasing durations. Affective discrimination of stimuli that are not recognized is a reliable phenomenon, but it occurs only within a narrow band of time. This parametric study has specified the relationship between exposure duration and affect and recognition judgments and has located that temporal window.

Affective discrimination of stimuli that are not recognized: II. Effect of delay between study and test

This study found that repeated exposure to briefly presented stimuli increased positive affect through familiarity without enhancing recognition of the stimuli. Following exposure, subjects selected previously shown target stimuli on the basis of affect in the absence of stimulus recognition. Interpreted in terms of the manner in which information can be accessed in long-term storage, this study extends earlier research by showing that the ability to select target stimuli by affect can occur undiminished over a delay of 1 week between study and test. Repeated processing during study can produce a form of perceptual learning, called perceptual fluency, that can serve as the basis for stimulus discrimination in the absence of recognition at the time of test. The present results of familiar, but unrecognized, stimuli are analogous to the memory phenomenon of deja vu.

Are false memories more difficult to forget than accurate memories? The effect of retention interval on recall and recognition

What is the effect of retention interval on accurate and false recollection in the Deese, Roediger, and McDermott (DRM) procedure? Previous research has suggested that false recall is more persistent than accurate recall, but the recognition results have been inconsistent. In two parametric studies, we tested recall and recognition for the same DRM lists, over retention intervals that ranged from no delay to a 2-month delay. We found that accurate and false memory were diminished by increases in retention interval, false memory persistence was present for recall and recognition, greater persistence for false memory than for accurate memory was more readily observed for recall than recognition, and the highthreshold (Pr), signal detection (d’), and nonparametric (A’) recognition measures differed in their sensitivity for detecting change. The effect of retention interval on accurate and false memory is consistent with expectations from fuzzy trace theory. In the DRM procedure, truth is not more memorable than fiction.

The mere exposure effect is differentially sensitive to different judgment tasks.

The mere exposure effect is the increase in positive affect that results from the repeated exposure to previously novel stimuli. We sought to determine if judgments other than affective preference could reliably produce a mere exposure effect for two-dimensional random shapes. In two experiments, we found that brighter and darker judgments did not differentiate target from distracter shapes, liking judgments led to target selection greater than chance, and disliking judgments led to distracter selection greater than chance. These results for brighter, darker, and liking judgments were obtained regardless of whether shape recognition was greater (Experiment 1) or not greater (Experiment 2) than chance. Effects of prior exposure to novel shapes were reliably observed only for affective judgment tasks. These results are inconsistent with general predictions made by the nonspecific activation hypothesis, but not the affective primacy or perceptual fluency hypotheses which were discussed in terms of cognitive neuroscience research.

A mere exposure effect for transformed three-dimensional objects: effects of reflection, size, or color changes on affect and recognition.

If the mere exposure effect is based on implicit memory, recognition and affect judgments should be dissociated by experimental variables in the same manner as other explicit and implicit measures. Consistent with results from recognition and picture naming or object decision priming tasks (e.g., Biederman & E. E. Cooper, 1991, 1992; L. A. Cooper, Schacter, Ballesteros, & Moore, 1992), the present research showed that recognition memory but not affective preference was impaired by reflection or size transformations of three-dimensional objects between study and test. Stimulus color transformations had no effect on either measure. These results indicate that representations that support recognition memory code spatial information about an object’s left-right orientation and size, whereas representations that underlie affective preference do not. Insensitivity to surface feature changes that do not alter object form appears to be a general characteristic of implicit memory measures, including the affective preference task.