Upright or inverted, entire or exploded: right-hemispheric superiority in face recognition withstands multiple spatial manipulations

Detecting implicit and explicit facial emotions at different ages

Emotions are processed in the brain through a cortical route, responsible for detailed-conscious recognition and mainly based on image High Spatial Frequencies (HSF), and a subcortical route, responsible for coarse-unconscious processing and based on Low SF (LSF). However, little is known about possible changes in the functioning of the two routes in ageing. In the present go/no-go online task, 112 younger adults and 111 older adults were asked to press a button when a happy or angry face appeared (go) and to inhibit responses for neutral faces (no-go). Facial stimuli were presented unfiltered (broadband image), filtered at HSF and LSF, and hybrids (LSF of an emotional expression superimposed to the HSF of the same face with a neutral expression). All stimuli were also presented rotated on the vertical axis (upside-down) to investigate the global analysis of faces in ageing. Results showed an overall better performance of younger compared to older participants for all conditions except for hybrid stimuli. The expected face-inversion effect was confirmed in both age groups. We conclude that, besides an overall worsening of the perceptual skill with ageing, no specific impairment in the functioning of both the cortical and the subcortical route emerged.

The effect of aging and emotions on time processing

BACKGROUND

Time perception is an automatic process that can be influenced by intrinsic and extrinsic factors.

AIMS

This study aimed to investigate the effect of age and emotions on the ability to keep track of short suprasecond intervals.

METHODS

Younger adults (N = 108, age range: 18-35) and older adults (N = 51, age range: 65-87) were asked to reproduce, bisect, or double the duration of facial stimuli randomly presented for 1500, 3000, and 4500 ms. The experiment included facial stimuli with positive, negative, or neutral expressions.

RESULTS

The participants across age correctly reproduced intervals but overestimated and underestimated them when asked to bisect and double the intervals, respectively. Overall, when faces were presented with a positive or negative expression, an overestimation of time intervals emerged compared to faces with neutral expressions. Emotions had a greater effect on older adults, who showed a greater overestimation of positive facial expressions and an underestimation of sad, but not angry, facial expressions.

DISCUSSION

The results provide evidence that time perception is influenced by age and emotions, with older adults showing a greater effect of emotions on time processing.

CONCLUSION

The study suggests an interaction among time processing, age, and emotions, highlighting an automatic relationship among these domains, often considered independent.

Crying the blues: The configural processing of infant face emotions and its association with postural biases

Several studies have exploited the face inversion paradigm to unveil the mechanisms underlying the processing of adult faces, showing that emotion recognition relies more on a global/configural processing for sadness and on a piecemeal/featural processing for happiness. This difference might be due to the higher biological salience of negative rather than positive emotions and consequently should be higher for infant rather than adult faces. In fact, evolution might have promoted specific adaptations aimed to prioritize the infant face by the attention system in order to foster survival during infancy, a rather long period during which the newborn depends entirely on adults. Surprisingly, no study has yet exploited this paradigm to investigate the processing of emotions from infant faces. In this study, the face inversion paradigm was used to explore emotion recognition of infant compared with adult faces in a sample of adult participants. In addition, the existence of potential differences associated with specific postural biases (e.g., the left-cradling bias) during interactions with infants was explored. The presence of rotational effects for the recognition of both happy and sad infant faces suggests that infant face emotions are predominantly processed in a configural fashion, this perceptual effect being more evident in sadness. Results are discussed in the context of the biological and social salience of the emotional infant face.

The Intricate Web of Asymmetric Processing of Social Stimuli in Humans

Although the population-level preference for the use of the right hand is the clearest example of behavioral lateralization, it represents only the best-known instance of a variety of functional asymmetries observable in humans. What is interesting is that many of such asymmetries emerge during the processing of social stimuli, as often occurs in the case of human bodies, faces and voices. In the present paper, after reviewing previous literature about human functional asymmetries for social and emotional stimuli, we suggest some possible links among them and stress the necessity of a comprehensive account (in both ontogenetic and phylogenetic terms) for these not yet fully explained phenomena. In particular, we propose that the advantages of lateralization for emotion processing should be considered in light of previous suggestions that (i) functional hemispheric specialization enhances cognitive capacity and efficiency, and (ii) the alignment (at the population level) of the direction of behavioral asymmetries emerges, under social pressures, as an evolutionary stable strategy.

Understanding the Impact of Face Masks on the Processing of Facial Identity, Emotion, Age, and Gender

The COVID-19 pandemic has introduced new challenges for governments and individuals. Unprecedented efforts at reducing virus transmission launched a novel arena for human face recognition in which faces are partially occluded with masks. Previous studies have shown that masks decrease accuracy of face identity and emotion recognition. The current study focuses on the impact of masks on the speed of processing of these and other important social dimensions. Here we provide a systematic assessment of the impact of COVID-19 masks on facial identity, emotion, gender, and age. Four experiments (N = 116) were conducted in which participants categorized faces on a predefined dimension (e.g., emotion). Both speed and accuracy were measured. The results revealed that masks hindered the perception of virtually all tested facial dimensions (i.e., emotion, gender, age, and identity), interfering with normal speed and accuracy of categorization. We also found that the unwarranted effects of masks were not due to holistic processes, because the Face Inversion Effect (FIE) was generally not larger with unmasked compared with masked faces. Moreover, we found that the impact of masks is not automatic and that under some contexts observers can control at least part of their detrimental effects.

How does hemispheric specialization contribute to human-defining cognition?

Uniquely human cognitive faculties arise from flexible interplay between specific local neural modules, with hemispheric asymmetries in functional specialization. Here, we discuss how these computational design principles provide a scaffold that enables some of the most advanced cognitive operations, such as semantic understanding of world structure, logical reasoning, and communication via language. We draw parallels to dual-processing theories of cognition by placing a focus on Kahneman's System 1 and System 2. We propose integration of these ideas with the global workspace theory to explain dynamic relay of information products between both systems. Deepening the current understanding of how neurocognitive asymmetry makes humans special can ignite the next wave of neuroscience-inspired artificial intelligence.

Human Lateralization, Maternal Effects and Neurodevelopmental Disorders

In humans, behavioral laterality and hemispheric asymmetries are part of a complex biobehavioral system in which genetic factors have been repeatedly proposed as developmental determinants of both phenomena. However, no model solely based on genetic factors has proven conclusive, pushing towards the inclusion of environmental and epigenetic factors into the system. Moreover, it should be pointed out that epigenetic modulation might also account for why certain genes are expressed differently in parents and offspring. Here, we suggest the existence of a sensitive period in early postnatal development, during which the exposure to postural and motor lateral biases, expressed in interactive sensorimotor coordination with the caregiver, canalizes hemispheric lateralization in the “typical” direction. Despite newborns and infants showing their own inherent asymmetries, the canalizing effect of the interactive context owes most to adult caregivers (usually the mother), whose infant-directed lateralized behavior might have been specifically selected for as a population-level trait, functional to confer fitness to offspring. In particular, the case of the left-cradling bias (LCB; i.e., the population-level predisposition of mothers to hold their infants on the left side) represents an instance of behavioral trait exhibiting heritability along the maternal line, although no genetic investigation has been carried out so far. Recent evidence, moreover, seems to suggest that the reduction of this asymmetry is related to several unfavorable conditions, including neurodevelopmental disorders. Future studies are warranted to understand whether and how genetic and epigenetic factors affect the lateralization of early mother-infant interaction and the proneness of the offspring to neurodevelopmental disorders.

Face Inversion Effect on Perceived Cuteness and Pupillary Response

The face inversion effect reflects the special nature of facial processing and appears not only in recognizing facial identity or expression but also in subjective evaluation, such as facial attractiveness. Previous studies have revealed that the way in which we perceive attractiveness (beauty versus cuteness) differs our perceptual behavior. Therefore, the face inversion effect on attractiveness might differ based on the viewpoint of attractiveness. In this study, we measured pupillary response when judging the cuteness of facial stimuli and focused on the mechanism of perceiving attractiveness in terms of the effect of involuntary physical reaction. We investigated whether perceived cuteness – a kind of attractiveness – was affected by face inversion and whether the face inversion effect appeared in pupillary responses. We then conducted experiments in which participants observed inverted faces and rated the subjective cuteness of the faces, and we measured the participants’ pupil size while they observed the facial stimuli. The results revealed a negative correlation between pupil changes and the perceived cuteness of inverted faces, which is consistent with the previous result of upright faces. Thus, we found that the perception of facial cuteness is little affected by face inversion, suggesting that the judgment of cuteness is processed differently from other types of attractiveness such as beauty. We also found that pupillary response is related to perceiving cuteness, which could lead to consistency in the perception of cuteness.

Assessing the presence of face biases by means of anorthoscopic perception

Anorthoscopy is a presentation mode in which an image is shown sliding behind a slit-shaped aperture, so that it is visible only part by part and never in its entirety. With the aims to assess (1) whether the processing of complex stimuli (faces) correctly occurs in anorthoscopy, and (2) whether the Own-Gender Bias (OGB: the better recognition of stimuli belonging to the same gender of the observer: faster and more accurate) and the Left-Face Bias (LFB: the preference to analyze the left half of the face) occur in such a part by part presentation, we presented female and male faces as whole stimuli (Experiment 1) and in anorthoscopy (Experiments 2 and 3), as well as female/male chimeric faces (Experiment 4), during a gender categorization task. Experiment 1 confirmed that participants correctly categorized the gender of faces, but the OGB was not found. In Experiments 2 and 3 we manipulated the direction (Experiment 2: upward/downward; Experiment 3: leftward/rightward), the speed (slow and fast) of the sliding faces, and the width of the aperture (small and large). Both tasks revealed that facial gender was correctly categorized in anorthoscopy. The OGB was found, but only for males/females in Experiments 2/3, respectively. In Experiment 4 the LFB emerged only in the tachistoscopic session, suggesting that this perceptual bias does not extend to anorthoscopy.

Voice gender categorization in the connected and disconnected hemispheres

The role of the left and right hemispheres in processing the gender of voices is controversial, some evidence suggesting a bilateral involvement, some others suggesting a right-hemispheric superiority. We investigated this issue in a gender categorization task involving healthy participants and a male split-brain patient: female or male natural voices were presented in one ear during the simultaneous presentation of white noise in the other ear (dichotic listening paradigm). Results revealed faster responses by the healthy participants for stimuli presented in the left than in the right ear, although no asymmetries emerged between the two ears in the accuracy of both the patient and the control group. Healthy participants were also more accurate at categorizing female than male voices, and an opposite-gender bias emerged - at least in females - showing faster responses in categorizing voices of the opposite gender. The results support a bilateral hemispheric involvement in voice gender categorization, without asymmetries in the patient, but with a faster categorization when voices are directly presented to the right hemisphere in the healthy sample. Moreover, when the two hemispheres directly interact with one another, a faster categorization of voices of the opposite gender emerges, and it can be an evolutionary grounded bias.

Time course of spatial frequency integration in face perception: An ERP study

Face perception is based on the processing and integration of multiple spatial frequency (SF) ranges. However, the temporal dynamics of SF integration to form an early face representation in the human brain is still a matter of debate. To address this issue, we recorded event-related potentials (ERPs) during the presentation of spatial frequency-manipulated facial images. Twenty-six participants performed a gender discrimination task on non-filtered, low-, high-, and band-pass filtered face images, corresponding, respectively, to the full range, spatial frequencies up to 8 cycles/image, above 32 cycles/image, and from 8 to 16 cycles/image. Behaviorally, the task related-performance was more accurate and faster for non-filtered (NF) and mid-range SF (MSF) than for low SF (LSF) and high SF (HSF) stimuli. At both behavioral and electrophysiological levels, response to MSF contained in faces did not differ from the responses to full spectrum non-filtered (NF) facial images. In ERPs, LSF facial images evoked the largest P1 amplitude while HSF facial images evoked the largest N170 amplitude compared with the other three conditions. Since LSFs and HSFs would transmit global and local information respectively, our observations lend further support to the "coarse-to-fine" processing theory of faces. Furthermore, they offer original evidence of the effectiveness and adequacy of the mid-range spatial frequency in face perception. Possible theoretical interpretations of our findings are discussed.

Split-brain patients: Visual biases for faces

Split-brain patients constitute a small subpopulation of epileptic patients who have received the surgical resection of the callosal fibers in an attempt to reduce the spread of epileptic foci between the cerebral hemispheres. The study of callosotomy patients allowed neuropsychologists to investigate the effects of the hemispheric disconnection, shedding more light on the perceptual and cognitive abilities of each hemisphere in isolation. This view that callosotomy completely isolates the hemispheres has now been revised, in favor of the idea of a dynamic functional reorganization of the two sides of the brain; however, the evidence collected from split-brain patients is still a milestone in the neurosciences. The right-hemispheric superiority found in the healthy population concerning face perception has been further supported with split-brains, and it has been shown that the right disconnected hemisphere appears superior to the left hemisphere in recognizing and processing faces with similar characteristics as the observers' (e.g., gender, identity, etc.). Even more controversial is the field of hemispheric asymmetries for processing facial emotion, some evidence suggesting a right-hemispheric superiority for all emotions, some others showing a complementary hemispheric asymmetry depending on the positive or negative emotional valence. Although the practice of callosotomy is mostly abandoned today in favor of pharmacological alternatives, further studies on the remaining split-brain patients could help advance our understanding of hemispheric specialization for social stimuli.

Face gender categorization and hemispheric asymmetries: Contrasting evidence from connected and disconnected brains

We investigated hemispheric asymmetries in categorization of face gender by means of a divided visual field paradigm, in which female and male faces were presented unilaterally for 150ms each. A group of 60 healthy participants (30 males) and a male split-brain patient (D.D.C.) were asked to categorize the gender of the stimuli. Healthy participants categorized male faces presented in the right visual field (RVF) better and faster than when presented in the left visual field (LVF), and female faces presented in the LVF than in the RVF, independently of the participants' sex. Surprisingly, the recognition rates of D.D.C. were at chance levels - and significantly lower than those of the healthy participants - for both female and male faces presented in the RVF, as well as for female faces presented in the LVF. His performance was higher than expected by chance - and did not differ from controls - only for male faces presented in the LVF. The residual right-hemispheric ability of the split-brain patient in categorizing male faces reveals an own-gender bias lateralized in the right hemisphere, in line with the rightward own-identity and own-age bias previously shown in split-brain patients. The gender-contingent hemispheric dominance found in healthy participants confirms the previously shown right-hemispheric superiority in recognizing female faces, and also reveals a left-hemispheric superiority in recognizing male faces, adding an important evidence of hemispheric imbalance in the field of face and gender perception.