Undoing suggestive influence on memory: The reversibility of the eyewitness misinformation effect

Presenting inconsistent postevent information about a witnessed incident typically decreases the accuracy of memory reports concerning that event (the misinformation effect). Surprisingly, the reversibility of the effect (after an initial occurrence) has remained largely unexplored. Based on a memory conversion theoretical framework and associated refined assessment strategy, we report three experiments to demonstrate that suggestive influence can be completely undone. Initially established misinformation effects were eliminated - even after a period of 5weeks (Exp. 3) - through (a) an enlightenment procedure ensuring an adequate representation of the memory task as a search for potentially two contradictory items (instead of "the" single "correct" answer) and (b) using a memory state test that unconfounds the performance contributions of item and source memory by assessing them separately. Specifically, memory for original event details that were the target of misinformation was restored to the level of non-misled control performance, and even beyond (Exp. 3). This remarkable reversibility of misinformation influence highlights the central role of memory conversion processes in the misinformation effect (but does not principally exclude the contribution of traditional interference processes). We discuss the compatibility of our findings with previous research and make suggestions for real-world eyewitness interrogation.     

Zur Häufigkeit der Schuldfähigkeitsbegutachtung von Sexualstraftätern im Erkenntnisverfahren

This study investigated how often and depending on which factors sexual offenders are examined by mental health experts regarding their criminal responsibility. Out of a total of 306 legal charges against sex offenders accused of child sexual abuse (CSA: n?=?145), rape or sexual assault (n?=?89), exhibitionism (n?=?39), sexual abuse of adolescents, mentally defective, physically helpless or warded persons (n?=?18) that were admitted by a criminal court in 2001 in the German federal state of Schleswig-Holstein, 209 (95.6 %) were analyzed regarding the following questions: how often was the accused examined by a mental health professional regarding mental responsibility? Was the chance of being examined systematically related to certain factors (e.g., personality of the accused)? Expert advice regarding the mental responsibility of the accused was obtained by the court in only 34 cases (11.7 %). No systematic relationships of personal variables as well as the modus operandi and the chance of commissioning a mental health expert were found. The main reason for assigning a forensic expert opinion was the vague impression of a psychic disorder. Re-offending increased the rate of a mental health examination only in CSA (34.6 % of re-offenders were examined compared to 9.2 % of first-time offenders), but not in rape or sexual assault. Also age does not predict the commissioning of an expert opinion. Only one fifth of all accused below the age of 21 were investigated by a mental health professional. Results are discussed in terms of legal background, consequences for risk assessment and relapse prevention.     

Comparing the influence of directly vs. indirectly encountered post-event misinformation on eyewitness remembering

Some research has found a stronger influence of directly (face-to-face; co-witness; ‘social’) vs. indirectly (through written reports, ‘non-social’) encountered post-event misinformation on eyewitness memory reports, whereas other research finds no (big) difference. We argue and demonstrate that a crucial but so far neglected variable underlying this difference is memory for the misleading information itself. In a study with N = 120 participants who encountered misinformation directly or indirectly, we found misinformation retention (as assessed in a separate test) to be positively associated with a broad range of misinformation effects. Influence type (direct vs. indirect), however, did not moderate the misinformation effect in terms of memory for original details, and misinformation endorsement was even weaker in the direct influence condition. In our view, these findings reflect differential conversion of retained misinformation into test performance. Other than this, influence type had essentially no effects on remembering; nor did an additional post-warning manipulation.     

Effects of pre-learning stress on memory for neutral, positive and negative words: Different roles of cortisol and autonomic arousal

Stress can have enhancing or impairing effects on memory. Here, we addressed the effect of pre-learning stress on subsequent memory and asked whether neutral and emotionally valent information are differentially affected by specific stress components, autonomic arousal and stress-induced cortisol. Ninety-six healthy men and women underwent either a stressor (modified cold pressor test) or a control warm water exposure. During stress, participants showed comparable autonomic arousal (heart rate, blood pressure), while 60 percent showed an increase of cortisol (responders vs. 40 percent non-responders). Ten minutes after the cold pressor test neutral, positive and negative words were presented. Free recall was tested 1 and 24 h later. Overall, positive and negative words were better recalled than neutral words. Stress enhanced the recall of neutral words independently of cortisol response. In contrast, the free recall of negative words was enhanced in cortisol responders in the 1-h but not 24-h test which might suggest different effects of cortisol on consolidation and reconsolidation processes. Recall for positive words was unaffected by stress-induced cortisol. To summarize, (i) pre-learning stress can enhance memory for neutral words independently of cortisol and (ii) stress effects on memory for negative words appear to rely on stress-induced cortisol elevations, the absence of this effect for positive words might be at least partly due to differences in arousal evoked by positive vs. negative words.     

Chronic stress modulates the use of spatial and stimulus-response learning strategies in mice and man

Acute stress modulates multiple memory systems in favor of caudate nucleus-dependent stimulus-response and at the expense of hippocampus-dependent spatial learning and memory. We examined in mice and humans whether chronic stress has similar consequences. Male C57BL/6J mice that had been repeatedly exposed to rats ("rat stress") used in a circular hole board task significantly more often a stimulus-response strategy (33%) than control mice (0%). While velocity was increased, differences in latency to exit hole, distance moved or number of holes visited were not observed. Increased velocity and performance during retention trials one day later indicates altered emotionality and motivation to explore in rat stressed mice. Forty healthy young men and women were split into "high chronic stress" and "low chronic stress" groups based on their answers in a chronic stress questionnaire ("Trier Inventory of Chronic Stress"-TICS) and trained in a 2D task. A test trial immediately after training revealed that participants of the "high chronic stress" group used the S-R strategy significantly more often (94%) than participants of the "low chronic stress" group (52%). Verbal self-reports confirmed the strategy derived from participants' choice in the test trial. Learning performance was unaffected by the chronic stress level. We conclude that one consequence of chronic stress is the shift to more rigid stimulus-response learning, that is accompanied by changes in motivational factors in mice.     

Control over location-based response activation in the Simon task: behavioral and electrophysiological evidence

In 4 Simon experiments the authors examined control over 2 routes of sensorimotor processing: response priming in the unconditional route and response selection via the conditional route. The Simon effect diminished as the frequency of noncorresponding trials increased. Location-based response priming was observed only when the stimulus followed a corresponding event but not after a noncorresponding trial. Therefore, the unconditional route appears to be suppressed whenever the task context indicates priming as potentially disadvantageous. Moreover, the task-irrelevant stimulus location was used for response selection as a function of correspondence probability. Although exact repetitions of stimulus-response sequences caused a marked speed-up of responses, this 3rd mechanism is independent of unconditional route suppression and frequency-based adjustments in the conditional route.     

Mental relaxation improves long-term incidental visual memory

Experimental evidence has linked increased arousal to enhanced memory retention. There is also evidence that procedures reducing arousal, i.e., mental relaxation, might improve memory, but conflicting results have been reported. To clarify this issue, we studied the effects of a single session of relaxation training on incidental visual long-term memory. Thirty-two relaxation-naive subjects viewed 280 slides without being told that there would be subsequent memory testing. Afterwards, subjects listened to a 12 min relaxation tape; 16 subjects relaxed by following the instructions (relaxation group), and the other 16 subjects pressed a button whenever a body part was mentioned (control group). While listening to the relaxation tape, high frequency heart rate variability (HRV) was greater and low frequency HRV was lower in the relaxation group, implying effective relaxation and increasing parasympathetic activation. The relaxation group had superior memory retention 4 weeks later (p = .004), indicating enhancement of long-term memory performance. This effect could not be explained by retroactive interference experienced in the control group because short-term memory performance immediately after the tape was slightly better in the control group. Retention of materials acquired after the relaxation session remained unaffected, suggesting relaxation has retrograde effects on memory consolidation. Our data demonstrate a favorable influence of relaxation on at least this aspect of learning. Our data also extend previous knowledge on the beneficial effects of ascending parasympathetic stimulation on memory retention in that enhanced long-term memory consolidation may also occur in the presence of central and descending parasympathetic activation triggered by willful psychomotor activity.     

Perception of vocal effort and distance from the speaker on the basis of vowel utterances

The sound pressure level of vowels reflects several nonlinguistic and linguistic factors: distance from the speaker, vocal effort, and vowel quality. Increased vocal effort also involves the emphasis of higher frequency components and increases in F0 and F1. This should allow listeners to distinguish it from decreased distance, which does not have these additional effects. It is shown that listeners succeed in doing so on the basis of single vowels if phonated, but not if whispered, and that they compensate for most of the between-vowel variation in level. The results obtained when listeners had to estimate vocal effort as well as distance suggest that an analysis of an utterance takes place at an early stage in auditory processing, before memories of episodes are stored.     

What a car does to your perception: Distance evaluations differ from within and outside of a car

Almost a century ago it was first suggested that cars can be interpreted as tools, but consequences of this assumption were never tested. Research on hand-held tools that are used to manipulate objects in the environment suggests that perception of near space is extended by using tools. Literature on environment perception finds perception of far space to be modulated by the observer’s potential to act in the environment. Here we argue that a car increases the action potential and modulates perception of far space in a way similar to how hand-held tools modulate perception of near space. Five distances (4 to 20 meters) were estimated by pedestrians and drivers before and after driving/walking. Drivers underestimated all distances to a larger percentage than did pedestrians. Underestimation was even stronger after driving. We conclude that cars modulate the perception of far distances because they modulate the driver’s perception, like a tool typically does, and change the perceived action potential.     

The Sounds of Sentences: Differentiating the Influence of Physical Sound,Sound Imagery,and Linguistically Implied Sounds on Physical Sound Processing

Both the imagery literature and grounded models of language comprehension emphasize the tight coupling of high-level cognitive processes, such as forming a mental image of something or language understanding, and low-level sensorimotor processes in the brain. In an electrophysiological study, imagery and language processes were directly compared and the sensory associations of processing linguistically implied sounds or imagined sounds were investigated. Participants read sentences describing auditory events (e.g., “The dog barks”), heard a physical (environmental) sound, or had to imagine such a sound. We examined the influence of the 3 sound conditions (linguistic, physical, imagery) on subsequent physical sound processing. Event-related potential (ERP) difference waveforms indicated that in all 3 conditions, prime compatibility influenced physical sound processing. The earliest compatibility effect was observed in the physical condition, starting in the 80–110 ms time interval with a negative maximum over occipital electrode sites. In contrast, the linguistic and the imagery condition elicited compatibility effects starting in the 180–220 ms time window with a maximum over central electrode sites. In line with the ERPs, the analysis of the oscillatory activity showed that compatibility influenced early theta and alpha band power changes in the physical, but not in the linguistic and imagery, condition. These dissociations were further confirmed by dipole localization results showing a clear separation between the source of the compatibility effect in the physical sound condition (superior temporal area) and the source of the compatibility effect triggered by the linguistically implied sounds or the imagined sounds (inferior temporal area). Implications for grounded models of language understanding are discussed.