Verbal overshadowing is a phenomenon where giving a verbal description of sensory input impairs formation of memories of that input. This was first reported by Schooler and Engstler-Schooler (1990) where it was shown that the effects can be observed across multiple domains of cognition which are known to rely on non-verbal knowledge and perceptual expertise. One example of this is memory, which has been known to be influenced by language. Seminal work by Carmichael and collaborators (1932) demonstrated that when verbal labels are connected to non-verbal forms during an individual's encoding process, it could potentially bias the way those forms are reproduced. Because of this, memory performance relying on reportable aspects of memory that encode visual forms should be vulnerable to the effects of verbalization.
Initial findings Schooler and Engstler-Schooler (1990) were the first to report findings of verbal overshadowing. In their study, participants watched a video of a simulated robbery and were instructed to either verbally describe the robber or engage in a control task. Those who engaged in giving a verbal description were less likely to correctly identify the robber from a test lineup, compared to those who engaged in the control task. A larger effect was detected when the verbal description was provided 20, rather than 5, minutes after the video, and immediately before the test lineup. A meta-analysis by Meissner and Brigham (2001) supported the effects of verbal overshadowing, showing a small but reliably negative effect.
General effects of verbal overshadowing
The effects of verbal overshadowing have been generalized across multiple domains of cognition that are known to rely on non-verbal knowledge and perceptual expertise, such as memory. Memory has been known to be influenced by language. Seminal work by Carmichael and collaborators (1932) demonstrated that labels attached to, or associated with, non-verbal forms during memory encoding can affect the way the forms were subsequently reproduced. Because of this, memory performance that relies on reportable aspects of memory that encode visual forms should be vulnerable to the effects of verbalization. Pelizzon, Brandimonte, and Luccio (2002) found that visual memory representations appear to incorporate visual, spatial, and temporal characteristics. It is explained as follows:
Hatano, Ueno, Kitagami, and Kawaguchi found that verbal overshadowing is likely to occur when participants verbally described targets in detail. Detailed verbal descriptions resulted in more frequently inaccurate descriptions that in turn created inaccurate representations in the memories of participants. Inaccuracies are also likely to occur when face recognition comes immediately after verbalization. Other forms of non-verbal knowledge affected by verbal overshadowing include the following:
Verbalization of stimuli leads to the disruption of non-reportable processes that are necessary for achieving insight solutions, which are distinct from language processes. Schooler, Ohlsson, and Brooks (1993) found that face recognition requires information that cannot be adequately verbalized, giving rise to difficulty in describing factors in recognition judgments. Subjects were less effective in solving insight problems when compelled to put their thoughts in words, which suggests that language may interfere with thought.
The verbal overshadowing effect was not seen when participants engaged in articulatory suppression. Performance was reduced in both the verbal and non-verbal description conditions. This is evidence that verbal encoding plays a role in face recognition.
By testing with distracting faces presented between study and test, Lloyd-Jones and Brown (2008) suggested a dual-process approach to recognition memory took place, that verbalization influenced familiarity-based processes at first, but its effects were later seen on recollection, when discrimination between items became more difficult.
Verbal overshadowing in facial recognition The verbal overshadowing effect can be found for facial recognition because faces are predominately processed in a holistic or configurable manner. (Tanaka & Farah, 1993; Tanaka & Sengco, 1997) Verbalizing one's memory for a face is done using a featural or analytic strategy, leading to a drift from the configurable information about the face and to impaired recognition performance. However, Fallshore & Schooler (1995) found that the verbal overshadowing effect was not found when participants described faces of races different from their own.
A study by Brown and Lloyd-Jones (2003) found that there was no verbal overshadowing effect found in car descriptions; it was only seen in facial descriptions. The authors noted that descriptions were no different on any measure including accuracy. It is suggested that less expertise in verbalizing faces rather than cars invokes a stronger shift in verbal and featural processing. This supports the concept of a transfer inappropriate retrieval framework and addresses some limitations of the effect.
Wickham and Swift (2006) suggested that the verbal overshadowing effect is not seen in describing all faces, and one aspect that determines this is distinctiveness. Results showed that typical faces produce verbal overshadowing, while distinctive faces did not. In studies of eyewitness reports, variation in response criteria given by participants influenced the quality of the descriptions generated and accuracy on identification task, known as the retrieval-based effect.
Face recognition was also impaired when subjects described a familiar face, such as a parent, or when describing a previously seen but novel face. Dodson, Johnson, and Schooler (1997) found that recognition was also impaired when participants were provided with a description of a previously seen face, and they were able to ignore provided versus self-generated descriptions more easily. This finding of verbal overshadowing suggested that eyewitness recognition is not only affected by their own descriptions, but of descriptions heard from others, such other eyewitness testimonies.
Voice recognition The verbal overshadowing effect has also been found to affect voice identification. Research shows that describing a non-verbal stimuli leads to a decrease in recognition accuracy. In an unpublished study by Schooler, Fiore, Melcher, and Ambadar (1996), participants listened to a tape-recorded voice, after which they were asked either to verbally describe it or to not do so, and then asked to distinguish the voice from 3 similar distractor voices. The results showed that verbal overshadowing impaired accuracy of recognition based on gut feeling, suggesting an overall verbal overshadowing for voice recognition.
Due to the forensic relevance of voices heard over the telephone and harassing phone calls that are often a problem for police, Perfect, Hunt, and Harris (2002) examined the influence of three factors on accuracy and confidence in voice recognition from a line-up. They expected to find an effect, because voice represents a class of stimuli that is difficult to describe verbally. This meets Schooler et al.'s (1997) modality mismatch criterion, meaning that describing the speakers age, gender, or accent is difficult, making voice recognition susceptible to the verbal overshadowing phenomenon. It was found that the method of memory encoding had no impact on performance, and that hearing a telephone voice reduced confidence but did not affect accuracy.
They also found that providing a verbal description impaired accuracy but had no effect on confidence. The data showed an effect of verbal overshadowing in voice recognition and provided yet another disassociation between confidence and performance. Although there was a difference in confidence level, witnesses were able to identify voices over the telephone as accurately as voices heard directly. The authors stated, "This effect is useful in the respect that it demonstrates that the lack of a confidence effect with verbal overshadowing is not due to low sensitivity of the confidence measure". (p. 979) The data from the study suggested that the main effect of verbal overshadowing was seen mainly in the telephone voices. They also stated, "However, because of the statistical limitations, it is perhaps best not to over-interpret this finding until it is replicated in a larger sample". (P.979)
Perfect, Hunt, and Harris (2002) did a small-scale study that showed a reliable verbal overshadowing effect on voice identification, thus confirming previous research that showed verbally describing a to-be-recognized (non-verbal) stimulus leads to decrease in recognition accuracy without reducing confidence. This disassociation between performance and confidence offers scope to test theoretical accounts of the verbal overshadowing phenomena, and it is an issue that has been neglected so far. A more recent study by Wilson, Seale-Carlisle, and Mickes (2017) found that confidence is predictive of accuracy in verbal overshadowing. They found that high confidence identifications are lower in accuracy compared to what was observed in the lineups. Other results from their study concluded that police should encourage reporting crimes immediately and take down descriptions of perpetrators as soon as possible in order to reduce the effects of verbal overshadowing.
Recognition criteria The verbal overshadowing effect may effect changes in recognition criteria rather than in processing style or underlying memory. One explanation for the effect is based on a shift in a person's recognition criteria, or increased hesitancy in choosing someone from a lineup. Verbalization leads witnesses to use more precise or exact recognition criteria, therefore lowering identification rates, the phenomena can be captured by a shift in recognition criteria.
Placement of recognition criteria affects performance. With conservative criteria, people are unwilling to identify anyone in a lineup, but with liberal criteria, identification rates are greater. The criterion effect is persistent and known to play a large part in recognition paradigms that allow voluntary responses, moreso when there is a tradeoff between quantity and accuracy. However, with the criterion effect controlled, confidence and perceived difficulty cannot account for the effects of verbalization.
The verbal overshadowing effect is caused by strict recognition criteria that only affect identification rates when a "not present" response is possible. Clare and Lewandowsky (2004) found that verbalization can have a positive effect on identification. Although resulting in fewer correct identifications from lineups, it also reduced the number of false identification rates within lineups. Because of this, verbalization may protect innocent suspects from being falsely identified as perpetrators, suggesting that not all effects of verbalization on eyewitnesses are bad.
With the standard description instructions in place, verbal overshadowing occurs because people have become more reluctant to identify someone from a lineup after they provide a description of the perpetrator. The criterion-effect explanation is one that accounts for a large verbal overshadowing effect in optional lineups, the absence of a verbal overshadowing effect with forced choice identification, and the advantageous effect of verbalization with optional-choice lineups.
Retrieval-based interference theory