Unmasking a shady mirror effect: recognition of normal versus obscured faces

Hockley, Hemsworth, and Consoli (1999) found that following the study of normal faces, a recognition test of normal faces versus faces wearing sunglasses produced a mirror effect: The sunglasses manipulation decreased hit rates and increased false-alarm rates. The stimuli used by Hockley et al. (1999) consisted of separate poses of models wearing or not wearing sunglasses. In the current experiments, we separately manipulated same versus different depictions of individual faces and whether or not the faces were partially obscured. The results of a simulation and four experiments suggest that the test-based, mirror effect observed by Hockley et al. (1999) is actually two separable effects.     

Modeling the effects of verbal and nonverbal pair strength on associative recognition

Operations that improve the accuracy of associative recognition can do so in qualitatively different ways. Increasing repetitions and study time increases hit rates but has small effects on false alarm rates, and the specific patterns of false alarms are dependent on the stimuli (e.g., pairs of words, pseudowords, faces, or Chinese characters). In contrast, manipulating the type of stimuli that make up pairs produces a robust mirror effect: The hit rate is greater, and the false alarm rate is lower, for better recognized stimuli. To explain these findings, a model of single-item recognition is extended to associative recognition. Within this dual-process framework, the present results suggest that words are encoded more extensively than nonverbal stimuli and that recognition of frequently encountered stimuli (words and faces) is more likely to be based on recollection than is recognition of uncommon stimuli (pseudowords and Chinese characters).     

The variance theory of the mirror effect in recognition memory

The mirror effect refers to a rather general empirical finding showing that, for two classes of stimuli, the class with the higher hit rates also has a lower false alarm rate. In this article, a parsimonious theory is proposed to account for the mirror effect regarding, specifically, high- and low-frequency items and the associated receiver-operating curves. The theory is implemented in a recurrent network in which one layer represents items and the other represents contexts. It is shown that the frequency mirror effect is found in this simple network if the decision is based on counting the number of active nodes in such a way that performance is optimal or near optimal. The optimal performance requires that the number of active nodes is low, only nodes active in the encoded representation are counted, the activation threshold is set between the old and the new distributions, and normalization is based on the variance of the input. Owing to the interference caused by encoding the to-be-recognized item in several preexperimental contexts, the variance of the input to the context layer is greater for highthan for low-frequency items, which yields lower hit rates and higher false alarm rates for high- than for low-frequency items. Although initially the theory was proposed to account for the mirror effect with respect to word frequency, subsequent simulations have shown that the theory also accounts for strength-based mirror effects within a list and between lists. In this case, consistent with experimental data, the variance theory suggests that focusing attention to the more difficult class within a list affects the hit rate, but not the false alarm rate and not the standard deviations of the underlying density, leading to no mirror effect.     

Influences of temporal factors on memory conjunction errors

Subjects viewed a series of faces presented two at a time for 16 seconds. Following either a 15‐minute (Experiment 1) or 24‐hour (Experiment 2) retention interval they received a recognition test that included old faces as well as faces constructed by recombining features from simultaneously presented study faces (simultaneous‐conjunction condition), faces from successive pairs (near‐conjunction condition), and faces that were two pairs apart (far‐conjunction condition). In Experiment 1, false alarm rates decreased as the temporal distance between the relevant study faces increased. In Experiment 2, the false alarm rate in the simultaneous‐conjunction condition was equal to the hit rate for old faces, and the false alarm rates for the other conditions was much lower. There was no effect of serial position during the study phase on the likelihood that parts of a face would later be miscombined to produce a recognition error in either experiment. The results suggest that witnesses to a crime are more likely to miscombine features of a to‐be‐remembered stimulus with those of another stimulus that was simultaneously present at the crime scene than with those of a stimulus encountered either earlier or later, especially when the test is delayed. Copyright © 2000 John Wiley & Sons, Ltd.     

The picture superiority effect in associative recognition

The picture superiority effect has been well documented in tests of item recognition and recall. The present study shows that the picture superiority effect extends to associative recognition. In three experiments, students studied lists consisting of random pairs of concrete words and pairs of line drawings; then they discriminated between intact (old) and rearranged (new) pairs of words and pictures at test. The discrimination advantage for pictures over words was seen in a greater hit rate for intact picture pairs, but there was no difference in the false alarm rates for the two types of stimuli. That is, there was no mirror effect. The same pattern of results was found when the test pairs consisted of the verbal labels of the pictures shown at study (Experiment 4), indicating that the hit rate advantage for picture pairs represents an encoding benefit. The results have implications for theories of the picture superiority effect and models of associative recognition.     

Weapons and Eye Contact as Instigators or Inhibitors of Aggressive Arousal in Police-Citizen Interaction1

A field experiment was conducted with police officers during the normal course of their traffic patrol duties. The purpose was to determine whether the presence of holstered weapons and mirror sunglasses affected the degree of aggressiveness expressed nonverbally, and reported on a mood scale by citizens halted for an information check (neutral condition) or in order to be given a traffic ticket (negative condition). Results indicated that subjects in the negative condition both expressed and reported more aggressivity when the police officer wore a weapon than when no weapon was visible. The use of sunglasses had no effect on aggressivity but resulted in the officer's being perceived more negatively, though he was not perceived more negatively when he wore a weapon. No sex differences in expressed or reported aggressivity were obtained, although some sex differences on measures of secondary interest did occur. The implications of these findings for research on the “weapons effect” and on policy regarding the visibility of police weapons and the wearing of sunglasses by police officers are discussed.     

The face typicality-recognizability relationship: Encoding or retrieval locus?

Using a crossover recognition memory testing paradigm, we tested whether the effects on face recognition of the memorability component of face typicality (Vokey & Read, 1992, 1995) are due primarily to the encoding process occurring during study or to the retrieval process occurring at test. At study, faces were either veridical in form or at moderate (Experiment 1) or extreme (Experiment 2) levels of caricature. The variable of degree of facial caricature at study was crossed with the degree of caricature at test. The primary contribution of increased memorability to increased hit rate was through increased distinctiveness at study. Increased distinctiveness at test contributed to substantial reductions in the false alarm rate, too. Signal detection analyses confirmed that the mirror effects obtained were primarily stimulus/memory-based, rather than decision-based. Contrary to the conclusion of Vokey and Read (1992), we found that increments in face memorability produced increments in face recognition that were due at least as much to enhanced encoding of studied faces as they were to increased rejection of distractor faces.     

Predicting individual false alarm rates and signal detection theory: A role for remembering

The relationships between hit, remember, and false alarm rates were examined across individual subjects in three remember-know experiments in order to determine whether signal detection theory would be consistent with the observed data. The experimental data differed from signal detection predictions in two critical ways. First, remember reports were unrelated, or slightly negatively related, to the commission of false alarms. Second, both response types (remembers and false alarms) were uniquely related to hit rates, which demonstrated that the hit rate cannot be viewed as the result of a single underlying strength process. These results are consistent with the dual-process signal detection model of Yonelinas (1994), in which performance is determined by two independent processes--retrieval of categorical context information (remembering) and discriminations based on continuous item strength. Remember and false alarm rates selectively tap these processes, whereas the hit rate is jointly determined. Monte Carlo simulations in which the dual-process model was used successfully reproduced the pattern in the experimental data, whereas simulations in which a signal detection model, with separate "old" and "remember" criteria, was used, did not. The results demonstrate the utility of examining individual differences in response types when one is evaluating memory models.     

Cognitive mechanisms of false facial recognition in older adults

Older adults show elevated false alarm rates on recognition memory tests involving faces in comparison to younger adults. It has been proposed that this age-related increase in false facial recognition reflects a deficit in recollection and a corresponding increase in the use of familiarity when making memory decisions. To test this hypothesis, we examined the performance of 40 older adults and 40 younger adults on a face recognition memory paradigm involving three different types of lures with varying levels of familiarity. A robust age effect was found, with older adults demonstrating a markedly heightened false alarm rate in comparison to younger adults for "familiarized lures" that were exact repetitions of faces encountered earlier in the experiment, but outside the study list, and therefore required accurate recollection of contextual information to reject. By contrast, there were no age differences in false alarms to "conjunction lures" that recombined parts of study list faces, or to entirely new faces. Overall, the pattern of false recognition errors observed in older adults was consistent with excessive reliance on a familiarity-based response strategy. Specifically, in the absence of recollection older adults appeared to base their memory decisions on item familiarity, as evidenced by a linear increase in false alarm rates with increasing familiarity of the lures. These findings support the notion that automatic memory processes such as familiarity remain invariant with age, while more controlled memory processes such as recollection show age-related decline.     

Strength-based mirror effects in item and associative recognition: Evidence for within-list criterion changes

Strength-based mirror effects occur when the hit rate is higher and the false alarm rate is lower following strongly encoded study lists than when following more weakly encoded study lists. In Experiments 1A and 1B, strength-based mirror effects were observed in separate tests of single item and associative recognition for random word pairs. In Experiment 2, strength-based mirror effects were again seen when item and associative recognition were tested together. Finally, in Experiments 3 and 4, opposing strength-based mirror effects were observed for item and associative recognition when individual words and word pairs were presented at different rates in the same study lists. Strength-based mirror effects could result from participants' adopting a more conservative decision criterion following strong lists than following weak ones. If this is the case for both item and associative recognition, the present results demonstrate that subjects can adopt different response criteria for different recognition tasks and can alternate between them on a trial-by-trial basis.     

Type I error rates and power analyses for single-point sensitivity measures

Experiments often produce a hit rate and a false alarm rate in each of two conditions. These response rates are summarized into a single-point sensitivity measure such as d', and t tests are conducted to test for experimental effects. Using large-scale Monte Carlo simulations, we evaluate the Type I error rates and power that result from four commonly used single-point measures: d', A', percent correct, and gamma. We also test a newly proposed measure called gammaC. For all measures, we consider several ways of handling cases in which false alarm rate = 0 or hit rate = 1. The results of our simulations indicate that power is similar for these measures but that the Type I error rates are often unacceptably high. Type I errors are minimized when the selected sensitivity measure is theoretically appropriate for the data.     

The word-frequency paradox in recognition

High-frequency words are recalled better than are low-frequency words, but low-frequency words produce higher hit rates in a recognition test than do high-frequency words. Two experiments provided new date on the phenomenon and also evidence relevant to the dual process model of recognition, which postulates that recognition judgments are a function of increments in item familiarity and of item retrievability. First, recall and recognition by subjects who initially performed a single lexical decision task were compared with those of subjects who also gave definitions of high-, low-, and very low-frequency target words. In the second experiment, subjects initially performed either a semantic, elaborative task or an integrative task that focused attention on the physical, perceptual features of the same words. Both experiments showed that extensive elaborative processing results in higher recall and hit rates but lower false alarm rates, whereas word frequency has a monotonic, linear effect on recall and false alarm rates, but a paradoxical, curvilinear effect on hit rates. Elaboration is apparently more effective when the potential availability of meaningful connections with other structures is greater (as for high-frequency words). The results are consistent with the dual process model.     

The Role of Recollection and Familiarity in the Context Variability Mirror Effect

Context variability refers to the number of preexperimental contexts that are associated with concepts. In four experiments, we investigated the basis for increased recognition memory for low context variability words. Low context variability was associated with greater recollection in the hit rates, and high context variability was associated with greater familiarity in the false alarms. Shortening the study time reduced recollection, but low context variability still influenced recollection in the hit rates. A modality change from study to test also reduced recollection but preserved recollective differences for low versus high context variability items. One interpretation of the results suggests that low context variability evokes more specific and, perhaps, idiosyncratic recollective associations during learning and that these associations support better recognition in the hit rates. By contrast, activating the larger number of associations for high context variability items may be mistaken for familiarity in the false alarm rates.     

Age differences in accuracy and choosing in eyewitness identification and face recognition

Studies of aging and face recognition show age-related increases in false recognitions of new faces. To explore implications of this false alarm effect, we had young and senior adults perform (1) three eye-witness identification tasks, using both target present and target absent lineups, and (2) and old/new recognition task in which a study list of faces was followed by a test including old and new faces, along with conjunctions of old faces. Compared with the young, seniors had lower accuracy and higher choosing rates on the lineups, and they also falsely recognized more new faces on the recognition test. However, after screening for perceptual processing deficits, there was no age difference in false recognition of conjunctions, or in discriminating old faces from conjunctions. We conclude that the false alarm effect generalizes to lineup identification, but does not extend to conjunction faces. The findings are consistent with age-related deficits in recollection of context and relative age invariance in perceptual integrative processes underlying the experience of familiarity.     

Subjective memorability and the mirror effect.

The mirror effect refers to the common finding that hit and false alarm rates on a recognition test are inversely related. The present research investigated the generality of the mirror effect (to rare words) and tested whether the effect might be grounded in accurate estimates of word memorability. The first 2 experiments showed that although high- and low-frequency words exhibit a mirror effect, rare words do not. Furthermore, contrary to expectations, Ss consistently (and mistakenly) predicted that memorability was directly correlated with frequency of usage. These findings weight against the idea that the mirror effect arises because of a S's ability to reject low-frequency lures on the grounds that such words would have been remembered had they appeared previously. Instead, the rejection of lures from different frequency categories may be determined by their semantic or phonemic overlap with list targets, and an analysis along these lines may help to explain why rare words constitute an exception to the otherwise ubiquitous mirror effect.     

Study time effects in recognition memory

We empirically tested the assumption that study time increases recognition accuracy because the storage of information is better when study time is longer as Shiffrin and colleagues have reported, an assumption common to parallel models of recognition. In the present study with 123 subjects, we examined the effect of item strength on four measures: hit rate, false alarm rate, d', and beta, for a single-word recognition task with longer study times than those usually used in the literature. Analysis indicated significant increase for hit rate and d' and a decrease in false alarm rate, as one goes from weak to stronger study conditions, and a change in ln(beta) when study time is greater than 1 sec. These results suggest that familiarization is one, but not the only, factor underlying the strength-mirror effect.     

Interactions between study task, study time, and the low-frequency hit rate advantage in recognition memory

In studies of episodic recognition memory, low-frequency words (LF) have higher hit rates (HR) and lower false alarm rates (FAR) than do high-frequency words (HF), which is known as the mirror pattern. A few findings have suggested that requiring a task at study may reduce or eliminate the LF-HR advantage without altering the LF-FAR effect. Other studies have suggested that the size of the LF-HR advantage interacts with study time. To explore such findings more thoroughly and relate them to theory, the authors conducted 5 experiments, varying study time and study task. The full mirror pattern was found only in 2 cases: the standard condition requiring study for a later memory test and a condition requiring a judgment about unusual letters. The authors explain their findings in terms of the encoding of distinctive features and discuss the implications for current theories of recognition memory and the word frequency effect.     

Face value: testing the utility of contextual face cues for face recognition

The presence of multiple faces during a crime may provide a naturally-occurring contextual cue to support eyewitness recognition for those faces later. Across two experiments, we sought to investigate mechanisms underlying previously-reported cued recognition effects, and to determine whether such effects extended to encoding conditions involving more than two faces. Participants studied sets of individual faces, pairs of faces, or groups of four faces. At test, participants in the single-face condition were tested only on those individual faces without cues. Participants in the two and four-face conditions were tested using no cues, correct cues (a face previously studied with the target test face), or incorrect cues (a never-before-seen face). In Experiment 2, associative encoding was promoted by a rating task. Neither hit rates nor false-alarm rates were significantly affected by cue type or face encoding condition in Experiment 1, but cuing of any kind (correct or incorrect) in Experiment 2 appeared to provide a protective buffer to reduce false-alarm rates through a less liberal response bias. Results provide some evidence that cued recognition techniques could be useful to reduce false recognition, but only when associative encoding is strong.     

False memories for compound words: Role of working memory

Subjects studied pairs of compound words; pair members were presented simultaneously (one above the other) for 2 sec or sequentially (one immediately following the other) for 1 sec each, and 6-sec interstimulus intervals separated the end of presentation of one pair and the start of that of another. A subsequent recognition test included within-pair and between-pair conjunction foils (recombinations of stimulus parts from the same study pair and from separate pairs, respectively). Previous experiments using faces as stimuli have demonstrated that when faces are presented simultaneously there are many more false alarms to within-pair than to between-pair conjunction items, and when faces are presented sequentially there is an equal number of false alarms in those two conditions. However, Experiment 1 showed that for compound word stimuli there were equally high false alarm rates toboth types of foils in both study conditions relative to completely new test items. Experiment 2 showed that when rehearsal of compound words was prevented, the pattern of conjunction errors was very similar to the one typically obtained for faces. In Experiment 3, subjects falsely recalled conjunctions of within-pair compound words but not conjunctions of between-pair words in the simultaneous-study condition; no conjunctions were recalled in the sequential-study condition. The results support the idea that working memory processing is necessary for binding stimulus parts together in episodic memory.     

Effects of saccadic bilateral eye movements on memory in children and adults: an exploratory study

The effects of saccadic bilateral (horizontal) eye movements on true and false memory in adults and children were investigated. Both adults and children encoded lists of associated words in the Deese-Roediger-McDermott paradigm followed by a test of recognition memory. Just prior to retrieval, participants were asked to engage in 30s of bilateral vs. vertical vs. no eye movements. For studied information, the results for adults replicated previous work; bilateral eye movements were demonstrated to increase the accuracy of memory by increasing the hit rate and reducing the false alarm rate for related and unrelated recognition test lures. The results for children also indicated an improvement in memory accuracy, and like adults, was due to both an increase in the hit rate and a reduction in the false alarm rate. In spite of these similarities, the effects of bilateral eye movements differed between adults and children for critical unstudied words; i.e., those associated with the theme of the list. Only in adults did, bilateral eye movements reduce associative false memories; children did not show a reduction in false memory for critical associates. This produced a dissociation between the effects of eye movements on associative false memory as a function of age. The results are discussed from a developmental perspective in terms of potential mechanisms underlying true and false memory.