Early visual areas seem not to be processing visual input in a neutral or passive way; rather, their activation seems to be the result of anticipatory, task-driven processes, constituting an active engagement with the environment

The Anticipatory and Task-Driven Nature of Visual Perception. Sebo Uithol, Katherine L Bryant, Ivan Toni, Rogier B Mars. Cerebral Cortex, bhab163, September 7 2021. https://doi.org/10.1093/cercor/bhab163

Abstract: Humans have a remarkable capacity to arrange and rearrange perceptual input according to different categorizations. This begs the question whether the categorization is exclusively a higher visual or amodal process, or whether categorization processes influence early visual areas as well. To investigate this we scanned healthy participants in a magnetic resonance imaging scanner during a conceptual decision task in which participants had to answer questions about upcoming images of animals. Early visual cortices (V1 and V2) contained information about the current visual input, about the granularity of the forthcoming categorical decision, as well as perceptual expectations about the upcoming visual stimulus. The middle temporal gyrus, the anterior temporal lobe, and the inferior frontal gyrus were also involved in the categorization process, constituting an attention and control network that modulates perceptual processing. These findings provide further evidence that early visual processes are driven by conceptual expectations and task demands.

Keywords: visual Categorization, MVPA, FMRI, conceptual knowledge

Discussion

We have shown that the nature of a stimulus (dogs or frogs) can be decoded from the fMRI data, primarily in left and right V1 and V2, and the right fusiform gyrus. Interestingly, the decoding accuracy was strongly dependent on the viewing task. Decoding image perception following superordinate-level questions was significantly less than following basic-level questions. This suggests that the activation in early visual areas is not solely driven by perceptual input, but a combination of the input and task properties, in line with “active vision” theories. This stronger decoding accuracy may be partly driven by the occurrence of more concrete predictions upon basic-level questions, but not entirely, since the cortical surface from which we can decode frogs and dogs is much larger than the cortical surface from which we can validate predictions.

Previous work shows that task properties (i.e., physical vs. semantic judgments) have an impact on the processing of object stimuli at several cortical sites, including ventral temporal and prefrontal regions (Harel et al. 2014). It has been shown that the usability of a presented object (e.g., tool vs. nontool) affects the occipitotemporal cortex differently (Bracci et al. 2017). Similarly, Nastase et al. (2017) found differences in brain response for a taxonomic versus an ethological judgment task in multiple brain regions, including occipital areas. These studies all found task-dependent processing of visual information, but only outside the primary visual areas. We, however, did find task dependence activation in primary visual areas. This may be due to the fact that our study has fewer categories (i.e., only 2 categories in 2 different tasks), compared to previous studies, which enhances statistical power drastically.

We speculated that prefrontal areas, specifically inferior frontal gyrus would be involved in modulating the activity in both temporal and visual areas. Indeed, these areas all seem to contain information about the task and stimulus identity, as reflected in above-chance decoding accuracy in Analyses 1 and 3.

The primate is an inherently visual animal, which is reflected in its elaborate visual system, including the so-called dorsal parietal and ventral temporal streams. It has been argued that the ventral, temporal stream evolved to allow an ever more abstract processing of the visual stimulus, which might provide the basis for our categorization behavior (Murray et al. 2019). In the ape and human lineages, this ability is more developed and possibly expanded to multisensory information (Bryant et al. 2019). As such, we expected that a network of prefrontal, temporal, and visual areas would underlie our capacity to use conceptual knowledge to process visual input. The anterior temporal cortex and the middle temporal gyrus, both bimodal association areas, are known to be involved in categorical decisions (Patterson et al. 2007). Indeed, it was possible to decode the level of abstraction of the required processing of the stimulus ventral anterior temporal cortex and middle temporal gyrus. The middle temporal gyrus result is particularly interesting, as it is close to the part of the temporal cortex that has most expanded and reorganized in the human, compared to the macaque, brain (Mars et al. 2018; Van Essen and Dierker 2007). The level of abstraction of the question itself could be decoded in a much larger set of cortical areas, including the inferior frontal cortex. Interestingly, these frontal and temporal areas are connected by specific sets of white matter fibers (i.e., the arcutate fasciculus and the inferior fronto-occipital fasciculus), some of which are particularly extended in the human lineage (Eichert et al. 2020). Our results suggest the involvement of these systems in tuning early visual processing for efficient task processing.

These results are in line with the framing of perception as a dynamic and task-driven process, tailored to the current needs of the cognitive system. Enactivist theories argue that cognition is not the representation of a pregiven world by a pregiven mind, but rather the enactment of a world and a mind on the basis of a history of the variety of actions that a being in the world performs. Within this view, perceptual capacities are embedded in a more encompassing biological, psychological, and cultural context (Varela et al. 1991). This active engagement with the environment is also suggested by more recent theoretical approaches to cognition (Hutto and Myin 2013; Myin and Degenaar 2014).

In line with this, we show that the early visual areas are tuned to those features in the environment that are relevant for the task at hand. The finding that left inferior frontal cortex shows significantly different activation patterns for basic-level and superordinate level judgment tasks suggests that the control this area exerts is not confined to behavioral control, but control over perceptual processing as well (Higo et al. 2011). This could also explain the absence of a univariate effect in our comparison of basic-level and superordinate-level trials. When perception is not a neutral process, but sense-making from the start, it would be equally task-driven in both conditions.

The finding of a behavioral difference suggests that the 2 decision processes (basic vs. superordinate) are not equally difficult. Superordinate categories are assumed to be less restricted in terms of visual input (e.g., the category “mammal” shows greater variance than the category “dog”). This increased difficulty is reflected by an increase in reaction time in the behavioral task. At the same time, the increased difficulty is reflected in a decrease of the cortical area from which the perceptual input could be decoded. Together with the fact that the increased difficulty is not reflected in gross brain activation (univariate BOLD result) during the viewing epoch of the imaging task, this suggests that the cortical areas are qually strongly but differently in nature involved in both tasks.

For efficient processing it is likely that task-dependent tuning to perceptual features primes the visual system before the actual perception. Indeed we have found evidence for expectations of upcoming stimuli in V1 and V2. A classifier trained on contrasting dog from frog questions was able to contrast dog from frog images as well. This anticipation surpasses low-level features such as lines and orientation, as different images were used per animal. This finding of modulation of V1 is in line with a recent reports showing that processes in V1 are biased by semantic categories (Ester et al. 2019) as well as action intentions (Gallivan et al. 2011). The finding of stimulus anticipation in V1 is in line with predictive coding accounts that recently have gained attention (Clark 2013; Rao and Ballard 1999). The influence of the level of the question we showed in V1 and V2 could partly be attributed to the presence of a concrete expectation of a dog or a frog in basic-level trials and the absence of such an expectation in superordinate trials, yet the cluster was far more extensive in the “levels” analysis compared with the anticipation analysis.

One could argue that the decreased decoding accuracy in superordinate trials is a consequence of differences in viewing behavior. Since participants were allowed to explore the presented image freely, it could be that viewing behavior in the superordinate condition was more variable. We did not collect eye-tracking data in order to quantify this potential difference, but the absence of a univariate results and the fact that the average difference in reaction time during the behavioral experiment between the 2 conditions was only 50 ms (note that the average saccades lasts 150–200 ms (Palmer 1999)), suggest that the contribution of differences in viewing behavior to the decoding effect is likely to be limited. Additionally, if indeed viewing behavior would play a role, one would expect this difference to be largest in the retinotopically organized occipital areas (e.g., V1). To the contrary, in our results, above-chance decoding is “preserved” in V1 and V2, and absent in more complex visual areas.

We cross-decoded questions and images, and questions and the gray screen between images and questions in order to check the nature of the anticipation present in early visual areas. The fact that we could not cross-validate questions and gray screens, but we could cross-validate questions and images suggests that the anticipation is a more complex phenomenon than mere sustained activity, and points toward more dynamical explanations (see for instance Wolff et al. 2017 for an example of such a model for working memory).

In all, these findings suggest that early visual areas are not processing visual input in a neutral or passive way. Rather their activation seems to be the result of anticipatory, task-driven processes, constituting an active engagement with the environment. These findings could have profound consequences for our understanding of how concepts are processed by the brain. Apparently, a frog-as-a-frog is processed differently than a frog-as-an-amphibian. Even the activity in the left temporal pole, which has been suggested to accommodate task-independent concept representations (Patterson et al. 2007), shows task-dependent modulation in our study. Our findings are thus more in line with classical pragmatists (Sellars 1963) and more recent enactivist (Hutto and Myin 2013) theories that suggests that the identity of a concept is (partly) grounded in the way a concept is used. This could provide a highly speculative, but interesting new explanation for the reported dependence of conceptual knowledge on perceptual systems (Barsalou et al. 2003): concepts can be seen as perceptual capacities, driven by parietal and prefrontal control processes, rather than internal representations. When concepts are much more use-based, as hypothesized, the question moves from how concepts are represented (Patterson et al. 2007), to how concepts acquire the stable character that they have in their (communicative) use. Part of the stability may be dependent on invariant structures outside of the brain, for instance in social practice or other behavioral patterns.

Diversity as a source of division requires taking seriously cultural differences & investing in resources to help facilitate common language and common culture that reduce coordination and communication costs while keeping diversity

Muthukrishna, M., Sep 2021. The Ties that Bind Us. LSE Public Policy Review, 2(1), p.3. http://doi.org/10.31389/lseppr.35

Abstract: This paper reviews the evolutionary literature on cooperation and the mechanisms proposed to explain the differences we see in the scale, breadth, and intensity of cooperation across societies, over history, and among behavioural domains. The most well-studied mechanisms that help societies sustain cooperation include kinship, reciprocity, reputation, signalling, norms, informal and formal institutions, and the competition between stable equilibria sustained by these mechanisms. I apply each of these mechanisms to the problem of reciprocity across the lifecycle. I then discuss how these same ties also tear us apart and what policies might help tie us back together.

JEL Codes: A12, A13, C71, J14, J18, Z1

Keywords: altruism, cooperation, evolution, norms, institutions

4. Conclusion: Tying Us Back Together

Returning to the topic at hand, reciprocity across the lifecycle may ultimately depend on levels of production and the division of consumption between workers and pensioners, as Nick Barr explains in his paper in this issue. But both production and attitudes towards this decision are shaped by the ties that bind us, the ties that tear us apart, and the competition between cultural-groups of different norms and institutions. Policy decisions can shape these norms, and there are guiding lessons from this literature.

4.1. Increasing the sense of “we”

The sense of “we” becomes weaker when society is fractured along ethnic, religious, and cultural lines. Immigration brings diversity that is a fuel for both innovation and economic growth, but it can also be a source of division and cooperation at subnational scales. Resolving this paradox of diversity [41] requires taking seriously cultural differences, measuring them [4], sustainably managing migration (or investing in infrastructure to reduce competition over resources), and investing in resources to help facilitate common language and common culture that reduce coordination and communication costs while retaining cultural diversity. There are difficult practical and ethical challenges in attempting to resolve the trade-offs diversity poses, but new innovations in simply measuring diversity along different dimensions is a first step toward tackling these challenges.

4.2. Moving from burden to benefit

Reinstating the traditional role of the retired as carers, if not also as sources of information, may also offer a model to move public perception from burden to benefit. Intergenerational care home-cum-childcare centers, such as South West London’s Nightingale House, offer a potential model [42] with reported benefits for both children and the elderly.

4.3. Reducing perceptions of zero-sum

Perceptions of zero-sumness can create a reality through psychological traps. If we assume that the world is more zero-sum, or that others are not trustworthy, it can be difficult to reach that next cooperative threshold or to take advantages of the present positive-sum opportunities. This in turn can lead to anti-social competitive behaviour. As research on the Joy of Destruction (JoD) game shows, people are more likely to engage in destructive competition versus productive competition [37, 38, 43, 44, 45]. In this game, people are presented with an opportunity to harm another player at some cost to themselves with no other interaction between the two parties. For example, taking £40 away from another player at a cost of £20 to themselves. Participants living in Namibia have shown a higher willingness to voluntarily harm themselves to cause greater harm to another than those living in Ukraine, while within Namibia, those in low rainfall regions compared to high rainfall regions show the same tendency to embrace harm, provided more harm is done to another. It has been argued that this is a function of zero-sum contexts where relative status can be maintained more easily by harming others than by working hard to access a scarce resource. Cultural evolution and behavioural science offer tools for shaping public perception under times of resource stress and slowed growth [8].

From 2020... When two sexually dimorphic androgen dependent facial traits are judged in concert, ornamental (facial hair) rather than structural masculine facial features (bones) underpin men’s intra-sexual judgments of formidability

Multivariate Intra-Sexual Selection on Men’s Perceptions of Male Facial Morphology. Valeriya Mefodeva, Morgan J. Sidari, Holly Chau, Brett Fitzsimmons, Gabrielle Antoine, Tessa R. Clarkson, Samuel Pearson, Anthony J. Lee & Barnaby J. W. Dixson. Adaptive Human Behavior and Physiology volume 6, pages143–169, Mar 17 2020. https://link.springer.com/article/10.1007%2Fs40750-020-00128-2

Abstract

Objectives: Intra-sexual selection has shaped the evolution of sexually dimorphic traits in males of many primates, including humans. In men, sexual dimorphism in craniofacial shape (i.e. facial masculinity) and facial hair have both been shown to communicate aspects of social and physical dominance intra-sexually. However, less attention has been given to how variation in physical and social dominance among receivers impacts on perceptions of facial masculinity and beards as intra-sexual signals of formidability.

Methods: In the current study, male participants (N = 951) rated male faces varying in masculinity and beardedness when judging masculinity, dominance and aggressiveness. These participants also responded to scales measuring their psychological dominance, sexual jealousy, status seeking, and masculine morphology (facial masculinity, facial hair, and height).

Results: Beardedness exerted strong effects over clean-shaven faces on ratings of masculinity, dominance, and aggressiveness. Trait ratings of masculinity, dominance, and aggressiveness rose linearly with increasing craniofacial masculinity. The significant facial masculinity × facial hair interaction suggests that beardedness caused strong effects on all trait ratings over clean-shaven faces at every level of facial masculinity. Participants with full beards also reported higher scores on dominance and assertiveness scales. Participants high in dominance and assertiveness also gave higher ratings for dominance, but not masculinity or aggressiveness, to bearded over clean-shaven faces. Participants low in intra-sexual jealousy rated clean-shaven and/or feminised faces as less dominant, less masculine, and less aggressive.

Conclusions: These findings demonstrate that facial hair enhances perceptions of masculinity, dominance, and aggressiveness above ratings of facial masculinity, potentially by augmenting masculine craniofacial features. Individual differences in intra-sexual dominance showed associations with judgments of facial hair but not facial masculinity. Our study demonstrates that when two sexually dimorphic androgen dependent facial traits are judged in concert, ornamental rather than structural masculine facial features underpin men’s intra-sexual judgments of formidability.

Discussion

A growing body of research implicates intra-sexual selection in shaping the evolution of men’s secondary sexual traits, dominance, and status seeking (Lukaszewski et al. 2016; Puts 2010; Rosenfield et al. 2020). The current study reports men’s ratings of masculinity, dominance, and aggressiveness for male faces increased linearly with craniofacial masculinity, being lowest for the least masculine faces and highest for the most masculine faces. Beards were also judged as more masculine, dominant, and aggressive than clean-shaven faces. However, the effects of craniofacial masculinity on judgments of male faces were dwarfed by the effect of facial hair, such that ratings for masculinity, dominance, and aggressiveness were higher at each level of facial masculinity for bearded compared to clean-shaven faces. Our findings replicate previous studies reporting that beards exert stronger effects than facial masculinity on judgments of men’s masculinity and dominance (Dixson et al. 2017c; Sherlock et al. 2017). As an example of the size of these effects, we report significantly higher ratings (all ps < .001) for bearded faces with very feminine facial shape over the most masculine clean-shaven faces for ratings of masculinity (d = .61), dominance (d = .45), and aggressiveness (d = .38), highlighting that facial hair potentially enhances male intra-sexual formidability through amplifying underlying masculine craniofacial features such as jaw width, facial length and width.

Converging evidence demonstrates that men’s facial masculinity predicts men’s intra-sexual formidability (Puts 2010; Sell et al. 2012). Men with more masculine faces have greater upper body strength (Fink et al. 2007; Windhager et al. 2011), fighting ability (Třebický et al. 2013, 2015, 2018; Zilioli et al. 2015), and higher mating success (Hill et al. 2013; Kordsmeyer et al. 2018) than less facially masculine men. The degree to which men are sensitive to other men’s secondary sexual traits, including facial masculinity, when assessing their dominance may vary due to their own physical and psychological dominance (Puts 2010; Sell et al. 2012; Watkins et al. 2010a, b). In the current study, we did not find that men high in social dominance (Hypothesis 1) or status seeking (Hypothesis 3) were less sensitive to facial masculinity when ranking male facial masculinity, dominance, or aggressiveness than less dominant men (Watkins et al. 2010b). We also tested whether men’s physical masculinity was negatively associated with their judgments of facial masculinity (Hypothesis 7). Thus, height is positively associated with men’s social dominance (Puts 2010), aggressiveness (Archer 2009), and fighting ability (Sell et al. 2012). While we found that height was negatively associated with judgments of male masculinised and feminised faces for ratings of masculinity, dominance, and aggressiveness, the significant interaction was driven by lower ratings for feminised rather than masculinised faces. This provides partial support that taller men are less sensitive to cues of facial dominance in male faces, but does not directly replicate past findings that height is negatively associated with dominance judgments for male facial masculinity (Watkins et al. 2010a). We also found that participants with higher self-reported facial masculinity gave higher ratings of dominance, masculinity, and aggressiveness. However, there were no associations between self-reported facial masculinity and self-reported social dominance, assertiveness, or success and dedication on men’s judgments of male facial masculinity.

Facially masculine men report more open sociosexualities (Boothroyd et al. 2008), greater interest in short-term relationships (Arnocky et al. 2018), having more short-term partners (Rhodes et al. 2005), and greater likelihood of poaching other men’s partners (Rhodes et al. 2013). Thus, men with more masculine faces and better developed secondary sexual characters may be less jealous of masculine looking men than their less masculine contemporaries. Indeed, previous research has shown that men’s height is negatively associated with their self-reported intra-sexual jealousy (Buunk et al. 2008). While we also found that taller men reported lower intra-sexual jealousy (r = −.279), we did not find that taller, more facially masculine, or bearded men were less jealous of facial masculinity in male faces. Instead, participants reporting lower intra-sexual jealousy rated clean-shaven and less masculine faces as less masculine, dominant, and aggressive than masculine or bearded faces. This could simply reflect that men attribute lower threat in mating contexts to less masculine and physically formidable looking men. However, with regards men’s intra-sexual jealousy and judgments of beardedness, to our knowledge the only study measuring associations between women’s sexual openness and attractiveness ratings of male facial hair reported a positive association between female sexual openness and preferences for beards (Stower et al. 2019). At present, there are no published data relating beardedness to men’s sociosexuality and whether the decision to wear facial hair is a reflection of men’s sociosexual attitudes is an important question for future research.

Compared to the body of research on intra-sexual selection and judgments of male facial masculinity, fewer studies have assessed individual differences in men’s dominance and their judgments of male beardedness. Past research has shown that bearded men reported higher aggressive sexism scores than clean-shaven men in the U.S.A and India (Oldmeadow and Dixson 2016), but not Sweden (Hellmer and Stenson 2016; Hellmer et al. 2018). Men with facial hair report feeling more masculine (Wood 1986) and had higher serum androgens (Knussman and Christiansen 1988) than men favouring a clean-shaven appearance. In the current study, self-reported beardedness was positively associated with self-perceived facial masculinity (r = .158) and self-reported dominance (r = .119). Participants who reported higher scores on dominance and assertiveness personality scales also gave significantly higher masculinity, dominance, and aggressiveness ratings to bearded but not clean-shaven faces compared to participants lower in dominance and assertiveness. These findings complement growing evidence that beards enhance intra-sexual communication of masculine social dominance (Craig et al. 2019; Dixson and Vasey 2012; Dixson et al. 2017c) and provide the first evidence that facial hair is positively associated with male self-perceived social dominance. Importantly, this correlation cannot determine whether socially dominant men choose to grow their beards or whether keeping a beard augments men’s self-reported social dominance due to positive social feedback from peers. There is some evidence that bearded men have higher mating success when sex ratios are more male-biased (Barber 2001) and that beards (and female preferences for them) are more common in larger cities, with low average incomes and high life expectancies (Dixson et al. 2017a). Future research exploring the causal effects of men’s grooming decisions on social dominance and mating success would be valuable.

Comparative research among nonhuman animals can shed light on the roles of facial masculinity and beards in intra-sexual communication. Researchers working on nonhuman animals distinguish between the role of male weaponry and ornamentation in intra-sexual competition, such that weapons are employed during direct physical confrontations whereas ornaments communicate status and dominance without necessarily being associated with physical formidability (McCullough et al. 2016). Weapons involved in direct competition and fights are rarely false signals of male quality (Berglund et al. 1996) and may augment attractiveness to females when selecting for males bearing direct benefits (Wong and Candolin 2005). Our results failed to support several past studies that found associations between men’s intra-sexual competitiveness and judgments of male facial masculinity. This was surprising as masculine facial structure is positively associated with men’s upper body strength (Fink et al. 2007; Windhager et al. 2011), muscularity (Holzleitner and Perrett 2016), stature (Zaidi et al. 2019) and fighting ability (Třebický et al. 2015; Zilioli et al. 2015). Mixed martial arts fighters with more masculine facial features are more often winners than less facially masculine fighters (Třebický et al. 2015; Zilioli et al. 2015) and fighters with greater anaerobic fitness are rated as better fighters (Třebický et al. 2018). Our results may have differed had we included more interactive behavioural paradigms rather than comparisons of self-report measures of dominance. For example, recent research in which men were assigned to compete in either violent or non-violent video games revealed that men who competed in violent video games were slower to retreat from a hypothetical physical confrontation with a masculine looking male, and were slower to recognise threatening facial expressions than participants in competing in non-violent video games (Denson et al. 2020). It may be beneficial to repeat our studies using more interactive experimental approaches to test whether psychologically and physically masculine men are less sensitive to masculine traits.

In contrast to sexually selected weapons, ornaments can communicate dominance without being directly involved in combat (McCullough et al. 2016). For example, in mountain gorillas (Gorilla beringei beringei) male dominance rank, success in male-male dyadic contests, and number of females in the social group is positively associated with cranial adipose crest size and back breadth (Wright et al. 2019). In some cases, weaponry may not reliably communicate physical formidability (Berglund et al. 1996). Thus, in male fiddler crabs (Uca mjoebergi) claw size is associated with attractiveness, resource holding, and in assessing fighting ability between rival males (Reaney et al. 2008). However, when males lose their claws during fights or due to predation the regrown claws are of similar size to their original claws but less robust, yet rival males are unable to discern weapon quality and overestimate their opponents fighting ability (Lailvaux et al. 2009). Similarly, male slender crayfish (Cherax dispar) with larger claws successfully dominate males with small claws despite any positive association between their claw size and muscle development (Wilson et al. 2009). Beardedness is possibly the most sexually dimorphic of men’s secondary sexual characters (Dixson et al. 2005; Grueter et al. 2015) and enhances ratings of age, masculinity, dominance, and aggressiveness by enlarging the size of the jaw (Dixson et al. 2017c), the midface (Sherlock et al. 2017) and the saliency of agonistic expressions (Dixson and Vasey 2012; Craig et al. 2019). However, facial hair is unlikely to reflect aspects of male fighting ability (Dixson et al. 2018a) and may serve to enhance perceptions of masculinity, dominance, and aggressiveness to curtail intra-sexual conflicts from escalating into costly physical contests. Future research investigating whether bearded men are more successful than their clean-shaven counterparts in social rather than physical forms of intra-sexual competition would be valuable. Presently, our study provides some support for a role of intra-sexual selection in men’s judgments of male facial masculinity and reports the first data on individual differences in men’s judgments of male facial hair, which suggest beards are intra-sexually selected badges of status.

Among middle-aged adults, greater television viewing in early to mid-adulthood was associated with lower gray matter volume; future studies are needed to better elucidate causality and directionality

Long-term television viewing patterns and gray matter brain volume in midlife. Ryan J. Dougherty, Tina D. Hoang, Lenore J. Launer, David R. Jacobs, Stephen Sidney & Kristine Yaffe. Brain Imaging and Behavior, Sep 6 2021. https://rd.springer.com/article/10.1007/s11682-021-00534-4

Abstract: The purpose of this study was to investigate whether long-term television viewing patterns, a common sedentary behavior, in early to mid-adulthood is associated with gray matter brain volume in midlife and if this is independent of physical activity. We evaluated 599 participants (51% female, 44% black, mean age 30.3 ± 3.5 at baseline and 50.2 ± 3.5 years at follow-up and MRI) from the prospective Coronary Artery Risk Development in Young Adults (CARDIA) study. We assessed television patterns with repeated interviewer-administered questionnaire spanning 20 years. Structural MRI (3T) measures of frontal cortex, entorhinal cortex, hippocampal, and total gray matter volumes were assessed at midlife. Over the 20 years, participants reported viewing an average of 2.5 ± 1.7 h of television per day (range: 0–10 h). After multivariable adjustment, greater television viewing was negatively associated with gray matter volume in the frontal (β = − 0.77; p = 0.01) and entorhinal cortex (β = − 23.83; p = 0.05) as well as total gray matter (β = − 2.09; p = 0.003) but not hippocampus. These results remained unchanged after additional adjustment for physical activity. For each one standard deviation increase in television viewing, the difference in gray matter volume z-score was approximately 0.06 less for each of the three regions (p < 0.05). Among middle-aged adults, greater television viewing in early to mid-adulthood was associated with lower gray matter volume. Sedentariness or other facets of television viewing may be important for brain aging even in middle age.

Frequent commenters on Facebook are more likely to be interested in politics & to have more polarized opinions; also, people who comment on articles in the real world use more toxic language on average than the public as a whole

The Distorting Prism of Social Media: How Self-Selection and Exposure to Incivility Fuel Online Comment Toxicity. Jin Woo Kim, Andrew Guess, Brendan Nyhan, Jason Reifler. Journal of Communication, jqab034, September 3 2021. https://doi.org/10.1093/joc/jqab034

Abstract: Though prior studies have analyzed the textual characteristics of online comments about politics, less is known about how selection into commenting behavior and exposure to other people’s comments changes the tone and content of political discourse. This article makes three contributions. First, we show that frequent commenters on Facebook are more likely to be interested in politics, to have more polarized opinions, and to use toxic language in comments in an elicitation task. Second, we find that people who comment on articles in the real world use more toxic language on average than the public as a whole; levels of toxicity in comments scraped from media outlet Facebook pages greatly exceed what is observed in comments we elicit on the same articles from a nationally representative sample. Finally, we demonstrate experimentally that exposure to toxic language in comments increases the toxicity of subsequent comments.