Recognition of Masked Faces in the Era of the Pandemic: No Improvement Despite Extensive Natural Exposure

Recognition of Masked Faces in the Era of the Pandemic: No Improvement Despite Extensive Natural Exposure. Erez Freud et al. Psychological Science, September 12, 2022. https://doi.org/10.1177/09567976221105459

Abstract: Face masks, which became prevalent across the globe during the COVID-19 pandemic, have had a negative impact on face recognition despite the availability of critical information from uncovered face parts, especially the eyes. An outstanding question is whether face-mask effects would be attenuated following extended natural exposure. This question also pertains, more generally, to face-recognition training protocols. We used the Cambridge Face Memory Test in a cross-sectional study (N = 1,732 adults) at six different time points over a 20-month period, alongside a 12-month longitudinal study (N = 208). The results of the experiments revealed persistent deficits in recognition of masked faces and no sign of improvement across time points. Additional experiments verified that the amount of individual experience with masked faces was not correlated with the mask effect. These findings provide compelling evidence that the face-processing system does not easily adapt to visual changes in face stimuli, even following prolonged real-life exposure.

Discussion

Face masks were an important tool in the effort to minimize COVID-19 virus transmission (Cheng et al., 2020). Accordingly, the years 2020 to 2022 provided an unprecedented opportunity to examine the effects of prolonged and frequent exposure to occluded faces on recognition abilities. Here, we have documented persistent quantitative and qualitative alterations in face-processing abilities for masked versus nonmasked faces, with no evidence of improvement in the processing of masked faces over time. Using a combined cross-sectional and longitudinal approach, we found that the CFMT scores for upright faces decreased by approximately 15% when masks were added to the faces. This reduction remained statistically constant across 20 months, a period of extensive exposure to masked faces. This finding suggests that the matured face-processing system did not benefit from the prolonged exposure. Additional experiments and analyses confirmed and extended this conclusion and showed that the consistent decrement in face processing of masked faces was evident even when individual differences in exposure to these faces were considered.

Another key finding is the consistent and robust reduction of the face-inversion effect for masked faces across all time points. In particular, the inversion effect was roughly 43% smaller for masked faces. The inversion effect is suggested to reflect difficulties extracting the configural relationships between face parts (Farah et al., 1995; Freire et al., 2000). Hence, the smaller inversion effect for masked faces may be taken as evidence that holistic processing is largely reduced (although not entirely abolished). This qualitative change in the processing of masked faces was consistent across time points, providing additional evidence for the rigidity of the matured face-processing system.

Why is there no improvement in masked-face recognition?

The consistent effect of masks across time points could reflect the rigidity of the matured face-processing system. In particular, face perception rapidly develops in infancy but is then subject to a prolonged developmental trajectory (Pascalis et al., 2011, 2020). In early childhood, face processing is shaped by experience with other faces (Bate et al., 2020). One of the best examples of this malleability comes from the other-race effect, which is evident early in life (Kelly et al., 2009) but could be reversed or disappear if a child is regularly exposed to other-race faces (De Heering et al., 2010; Sangrigoli et al., 2005). In contrast, in adulthood, face-processing mechanisms are already in place and are less likely to be affected by experience (Pascalis et al., 2020; White, Kemp, Jenkins, Matheson, & Burton, 2014; Yovel et al., 2012). Here, we show that even extensive, naturalistic exposure to masked faces is not sufficient to facilitate the recognition of these faces, even though the eyes region, which is disproportionally critical for face recognition (Butler et al., 2010; Caldara et al., 2005; Royer et al., 2018; Tardif et al., 2019), remains uncovered.

An additional account for the lack of improvement in recognizing masked faces relates to the nature of the interaction. One can argue that mere exposure to masked unfamiliar faces may not suffice to revamp face-processing mechanisms. However, we note that daily encounters with masked people typically include more than just passive viewing. For example, in the grocery store, a person may need to identify their neighbor or their preferred cashier. An office worker needs to recognize peers and customers. Parents who pick up their children from school interact with other parents, children, and teachers. Hence, daily experiences provide a rich arena of exposures and the need to recognize masked faces. Yet our data suggest that such naturalistic exposures and interactions might be insufficient in eliciting adaptation of the face-processing system. A more refined view is that improvement in face-processing abilities in adulthood depends on deliberate, systematic training programs and does not rely on naturalistic exposure. This view is supported by recent studies that show effects of systematic training programs that include individuation tasks (McGugin et al., 2011; Yovel et al., 2012) and ongoing feedback (White, Kemp, Jenkins, & Burton, 2014). Note, however, that even these systematic training programs bring only very moderate improvement in face recognition.

The results could also be attributed to another intriguing possible mechanism; the current situation may be part of a vicious circle, one that reduces the chances to improve. On the one hand, there is massive exposure to masked faces, which, in many cases, require effective recognition. On the other hand, however, people have the chance to meet and to encounter nonmasked people in the privacy of their homes or via electronic media. It is possible, therefore, that such a hybrid state of affairs provides the system with a convenient escape from effectively dealing with masked faces. In other words, the current situation may limit the system’s ability to adapt, even in the face of a clear need to do so. This proposed mechanism could account for the lack of improvement that we report (almost) 2 years into the pandemic. An intriguing question is for how long such lack of improvement could persist. This, of course, depends on the extent and length of the pandemic.

Finally, the observed limited malleability of the matured face-processing system raises important questions about the ability of children to improve in recognizing masked faces. A recent study reported that in school-age children, masks hinder face-processing ability to a similar or even greater extent compared with adults (Stajduhar et al., 2022). Whether children exhibit improved masked-face recognition following prolonged exposure to masked faces in everyday life remains to be determined.

Limitations

The current investigation is timely and unique and benefits from the large sample size and combination of approaches. However, there are still important limitations that should be addressed in future studies. First, although the CFMT is a reliable test that has been used extensively over the past two decades (Bobak et al., 2016; Russell et al., 2009), the faces included in this test are all Caucasian men. Given the gender effect observed in our data as well as by other groups (Bobak et al., 2016), it is important to examine the reported effects using other, more diverse tests (Scherf et al., 2017). Another concern regards the ecological validity of the CFMT. Specifically, external face cues, which are important for real-life face recognition, are not available in this test. This concern might be more detrimental in the case of masked faces. However, it is important to note that previous studies reported correlations between CFMT scores and subjective reports of face-recognition abilities (Shah, Gaule, et al., 2015), between the CFMT and other measurements of face-processing abilities (DeGutis et al., 2013; Russell et al., 2009), and, most importantly, between CFMT scores and naturalistic assessments of face-perception abilities (Balas & Saville, 2017). It is also worth noting that previous studies demonstrated the existence of the mask effect for other test and image sets, including the GFMT (Carragher & Hancock, 2020; see also the control experiment described above) and the Karolinska Directed Emotional Faces (Marini et al., 2021), in which external face cues are preserved.

The concern regarding ecological validity also applies to the absence of other cues that might facilitate person recognition, such as motion, voice, and body shape. Importantly, however, it is established that faces play a superior role in person recognition even when other cues are available (Hahn et al., 2016). This is demonstrated in cases of prosopagnosia, which is experienced in daily life even when all cues are available.

Another limitation of the current image set (as well as other image sets used in previous studies) is that the masks were added to existing pictures in an artificial manner. This might lead to an omission of face shape cues that are normally available and plausibly critical for recognizing masked faces in naturalistic settings. Although we cannot rule out the detrimental effect of the artificial mask on face perception, a recent study by Marini and colleagues (2021) demonstrated the existence of a mask effect even for transparent masks that reveal important cues from the lower part of the face. Hence, it is unlikely that the mask effect observed here, especially the lack of improvement in face perception for masked faces, is solely due to the nature of the stimuli.