In Empathic Responses for Pain in Facial Muscles Are Modulated by Actor’s Attractiveness and Gender, and Perspective Taken by Observer (Jankowiak-Siuda et al., 2019) it is shown that people show more empathic responses towards females and less attractive faces expressing pain. Specifically, it was "investigated whether the sex and attractiveness of persons experiencing pain affected muscle activity associated with empathy for pain, the corrugator supercili (CS) and orbicularis oculi (OO) muscles, in male and female participants in two conditions: adopting a perspective of “the other” or “the self.”" The gender effect was larger than the attractiveness (or rather: lack thereof) effect. The greater responses towards less attractive faces could be explained by the association between lack of low attractiveness to "poor health, lower immunity, and fewer resources to cope with pain", which could increase (A) negative affect or (B) increase empathy for the pain of such people. The greater responses towards female faces were attributed to women being seen as more "sensitive to pain, fragile, and requiring more care and support".

The authors of The Confounded Nature of Angry Men and Happy Women (Becker et al., 2007) found:

Findings of 7 studies suggested that decisions about the sex of a face and the emotional expressions of anger or happiness are not independent: Participants were faster and more accurate at detecting angry expressions on male faces and at detecting happy expressions on female faces. These findings were robust across different stimulus sets and judgment tasks and indicated bottom-up perceptual processes rather than just top-down conceptually driven ones. Results from additional studies in which neutrally expressive faces were used suggested that the connections between masculine features and angry expressions and between feminine features and happy expressions might be a property of the sexual dimorphism of the face itself and not merely a result of gender stereotypes biasing the perception.

The author of The influence of perceived suffering and vulnerability on the experience of pity (Dijker, 2001) showed that "participants' pity reactions to photographs of persons expressing pain were influenced by age-related, sex-related, and postural vulnerability cues", that increased musculature evokes lower levels of pity from others and that "females received higher ratings on [protective tendency], pity and its perceptual correlates than males".

In Facial resemblance to emotions: Group differences, impression effects, and race stereotypes. (Zebrowitz et al., 2010) the authors demonstrate that "neutral expression male faces objectively resemble angry expressions more than female faces do [because female faces retain more neotenous characteristics than do male faces], female faces objectively resemble surprise expressions more than male faces do [again because female faces retain more neotenous characteristics than do male faces], White faces objectively resemble angry expressions more than Black or Korean faces do, and Black faces objectively resemble happy and surprise expressions more than White faces do". Furthermore, they say that while "both cultural stereotypes and structural commonalities could provide viable explanations for previous studies showing that sex and race moderated the recognition of angry, surprise, and happy emotion expressions and vice versa", the authors demonstrated that there are "similarities between emotion expressions and faces from various demographic categories that are due purely to structure". This sexual dimorphism w.r.t. anger was found to be smaller in Asian faces, but not the sexual dimorphism w.r.t. surprise.

The authors of Self-protective biases in group categorization: Threat cues shape the psychological boundary between “us” and “them”. (Miller et al., 2010) showed that the "presence of masculine cues biased people toward greater outgroup categorization". Specifically, masculine voices voices were categorized as black by white study participants, as were computer-generated point-light displays of human walkers with varying signs of masculinity. This effect increased when the walker was shown approaching the participants as opposed to side-walking, as a "target moving toward the perceiver connotes a potential source of imminent danger". Angry male faces also biased people toward greater outgroup categorization. Fear arousal resulted in a higher identification of threatening (i.e. angry), racially ambiguous male faces as Black, but only among White individuals who believed they were highly vulnerable to interpersonal danger.

According to Face gender and emotion expression: Are angry women more like men? (Hess et al., 2009) people identify androgynous angry faces as more likely to be a man than a woman and are slower to classify an angry woman as a woman than an angry man as a man. Happiness and fear expressions bias sex perception toward the female, whereas anger expressions bias sex perception toward the male.

The authors of Emotion in the neutral face: A mechanism for impression formation? (Adams Jr. et al., 2011) "found that neutral female versus neutral male faces were rated as more submissive, affiliative, naïve, honest, cooperative, babyish, fearful, happy, and less angry than neutral male faces".

In Gender and the Communication of Emotion Via Touch (Hertenstein & Keltner, 2010) it was found:

In the current reanalysis, we found that anger was communicated at greater-than-chance levels only when a male comprised at least one member of a communicating dyad. Sympathy was communicated at greater-than-chance levels only when a female comprised at least one member of the dyad. Finally, happiness was communicated only if females comprised the entire dyad.

The authors of Human Tears Contain a Chemosignal (Gelstein et al., 2011) found that "merely sniffing negative-emotion–related odorless tears obtained from women donors induced reductions in sexual appeal attributed by men to pictures of women’s faces. Moreover, after sniffing such tears, men experienced reduced self-rated sexual arousal, reduced physiological measures of arousal, and reduced levels of testosterone. Finally, functional magnetic resonance imaging revealed that sniffing women’s tears selectively reduced activity in brain substrates of sexual arousal in men".

In Caring or daring? Exploring the impact of facial masculinity/femininity and gender category information on first impressions (Walker & Wänke, 2017) masculine-looking persons were shown to be seen as colder and more competent than feminine-looking persons, and this effect was not only also found for atypical (masculine-looking women and feminine-looking men) category members but was even more pronounced. According to the authors, "very subtle facial cues to masculinity/femininity strongly guide first impressions and may have more impact than the gender category".

In Sex Related Factors in the Perception of Threatening Facial Expressions (Goos & Silverman, 2002) the authors showed that anger posed by males could be more accurately read from their faces than anger posed by females. A second hypothesis, namely that female-posed anger would be more accurately perceived by women than by men, received only partial support. Anger and disgust generated a lot of false alarms when reading male but not female faces, while fear and sadness generated more false alarms when reading female than male faces. People were significantly more sensitive to men's anger and women's fear and sadness.

According to The social face of emotion recognition: Evaluations versus stereotypes (Bijlstra et al., 2010), anger is more readily perceived on male faces, while sadness is more readily perceived on female faces.

The authors of Model Gender Interacts With Expressed Emotion to Enhance Startle: Angry Male and Happy Female Faces Produce the Greatest Potentiation (Åsli & Øvervoll, 2020) write:

The present experiment investigated startle EMG responses to a startle probe while viewing pictures of neutral, happy, angry, fearful, and sad facial expressions presented by female and male models. Participants were divided into female and male groups. Results showed that emotional facial expressions interact with model gender to produce startle potentiation to a probe: greater responses were found while viewing angry expressions by male models, and while viewing happy faces by female models.

The authors of Is Self-Sacrificial Competitive Altruism Primarily a Male Activity? (McAndew & Perilloux, 2012) studied self-sacrificial prosocial behavior in small groups by letting them play a game "in which the monetary success of a three-person group depended upon one of its members volunteering to endure pain (a cold stressor test) and inconvenience (being soaked in a dunk tank)". They also state that across groups, "the behavior of the altruist was judged to be more costly, challenging, and important and he/she was liked better, rewarded with more money, and preferred as a future experimental partner" and finally, that "[g]roups containing two males showed more evidence of competition to become altruists than groups containing two females, and personality traits were more effective predictors of altruistic behavior in males than in females". They conclude "that competition between males and “showing off” are key factors in triggering self-sacrificial altruistic behavior".

Punishment Preferences

In the UK, 3/4 to 5/6 male prisoners would not be in prison if they were treated as leniently as women.

In Estimating Gender Disparities in Federal Criminal Cases (Starr, 2012) it was found that women were twice as likely to avoid incarceration entirely and that men got 63% longer sentences for the exact same crimes. Discrimination against men was found to be over 6 times as high as discrimination against minorities found using the same methodology and the same author in Racial Disparity in Federal Criminal Charging and Its Sentencing Consequences (Rehavi & Starr, 2012).

In Racial, Ethnic, and Gender Disparities in Sentencing: Evidence from the U.S. Federal Courts (Mustard, 2001) it was shown that after controlling for numerous characteristics, male offenders receive substantially longer sentences. These disparities were primarily generated by departures from guidelines (70%), rather than differential sentencing within the guidelines (30%). Women were also more likely to get no prison term at all, more likely to be given downard departures (judges giving less than the minimum prison sentence) and less likely to be given upward adjustments (judges giving more than the maximum prison sentence). All in all, this means that judges specifically go out of their way to help women.

The authors of Demographic Differences in Sentencing: An Update to the 2012 Booker Report (Pryor et al., 2017) found:

Female offenders of all races received shorter sentences than White male offenders during the Post-Report period, as they had for the prior four periods. […] White female offenders received sentences that were 28.9 percent shorter than those of White male offenders in the Post-Report period, compared to 31.1 percent shorter during the Gall period. Black female offenders and Other Race female offenders also received shorter sentences than White male offenders during the Post-Report period, at 29.7 percent and 35.4 percent shorter respectively. In the Gall period these differences were 33.1 percent and 34.6 percent, respectively. Hispanic female offenders received sentences that were 16.8 percent shorter than those of White male offenders during the Post-Report period, compared to 18.2 percent shorter in the Gall period.

In Spouse Murder Defendants in Large Urban Counties, U.S. Department of Justice, 1995 it is shown:

Wives [who murdered their husbands] received shorter prison sentences than husbands [who murdered their wives] (a 10-year difference, on average) even when the comparison is restricted to defendants who were alike in terms of whether or not they were provoked — The average prison sentence for unprovoked wife defendants was 7 years, or 10 years shorter than the average 17 years for unprovoked husband defendants.

The authors of "Sentencing Disparity and Discrimination: A Focus on Gender", chapter 4 of "How Do Judges Decide? The Search for Fairness and Justice in Punishment" (Daly & Tonry, 1997) note that "offenders convicted of crimes against women were more than two-and-a-half times more likely to be sentenced to death".

In Does Victim Gender Increase Sentence Severity? Further Explorations of Gender Dynamics and Sentencing Outcomes (Curry et al., 2004) the following was shown:

Using data for offenders convicted of three violent crimes in the seven largest metro counties in Texas in 1991, the authors find evidence that offenders who victimized females received substantially longer sentences than offenders who victimized males. Results also show that victim gender effects on sentence length are conditioned by offender gender, such that male offenders who victimize females received the longest sentence of any other victim gender/offender gender combination.

The authors of Chivalry is Not Dead: Murder, Gender, and the Death Penalty (Shatz & Shatz, 2011) state:

Women guilty of capital murder are far less likely than men to be sentenced to death, and defendants who kill women are far more likely to be sentenced to death than defendants who kill men. We argue that all of these findings are consistent with chivalric norms, and we conclude that, in the prosecutors' decisions to seek death and juries' decisions to impose it, chivalry appears to be alive and well.

The authors of Justice Needs a Blindfold: Effects of Gender and Attractiveness on Prison Sentences and Attributions of Personal Characteristics in a Judicial Process (Ahola et al., 2009) found:

This study examined the effect of gender and facial characteristics of criminal offenders on attributions of crime-relevant traits. The stimulus pictures portrayed women and men of varying attractiveness. Participants were presented with pictures of these female or male faces along with accompanying crime accounts. The crime account described the individual in the picture as a person who had committed one of the following crimes: theft, fraud, drug crime, child molestation, child abuse, or homicide. After reading one case account the participants were asked to evaluate the credibility and other crime-relevant personality traits of the offender. Results showed that female defendants were rated more favourably than were male defendants. Gender worked to the advantage of the female perpetrator. There were also slight tendencies towards more lenient appraisal of the more attractive women.

According to a report titled Do You Receive a Lighter Prison Sentence Because You Are a Woman? An Economic Analysis of Federal Criminal Sentencing Guidelines (Sarnikar et al., 2007) which examined US criminal sentencing data, if women were treated like men in the end stage of the criminal justice system they would on average serve 9.5 months longer, and since according to the same report women serve on average 17 months they would receive a 56% sentencing length increase if they were sentenced like men. Since this report only took into account the end stage of the criminal justice system as that is all the data permitted, this gap is even larger in practice. They also state that "most of the gender gap arises from convictions via guilty pleas".

According to Police Brutality a Leading Cause of Death Among Young Men. DiversityInc. (2019), police violence against men is incomparably more prevalent than it is against minorities, although it is particularly prevalent towards African American males. In this image which is taken from Risk of police-involved death by race/ethnicity and place, United States, 2012–2018 (Edwards et al., 2018), African American females and White males are circled for emphasis. Police brutality is a male problem first, a race problem second.

Female prisoners are treated better in prison, see e.g. It's not fair on men that women prisoners don't have to wear uniforms. Tony MP. (Stone, 2015). Yet, there are calls to abolish prison for women, see e.g. Opinion: 8% of prisoners are women. That’s about 8% too many, Women will only be jailed for serious crimes, Justice Secretary reveals and What happens to mums and women who walk free from court.

In The Effects of Physical Attractiveness, Race, Socioeconomic Status, and Gender of Defendants and Victims on Judgments of Mock Jurors: A Meta-Analysis (Mazzella & Feingold, 1994) the authors show that women are punished less than men for the same crime and that defendants were at a disadvantage when their victim was female.

The authors of Perceived Masculinity Predicts U.S. Supreme Court Outcomes (Chen et al., 2016) state:

Previous studies suggest a significant role of language in the court room, yet none has identified a definitive correlation between vocal characteristics and court outcomes. This paper demonstrates that voice-based snap judgments based solely on the introductory sentence of lawyers arguing in front of the Supreme Court of the United States predict outcomes in the Court. In this study, participants rated the opening statement of male advocates arguing before the Supreme Court between 1998 and 2012 in terms of masculinity, attractiveness, confidence, intelligence, trustworthiness, and aggressiveness. We found significant correlation between vocal characteristics and court outcomes and the correlation is specific to perceived masculinity even when judgment of masculinity is based only on less than three seconds of exposure to a lawyer’s speech sample. Specifically, male advocates are more likely to win when they are perceived as less masculine. No other personality dimension predicts court outcomes. While this study does not aim to establish any causal connection, our findings suggest that vocal characteristics may be relevant in even as solemn a setting as the Supreme Court of the United States.

As the authors stated, this study does not aim to establish a causal connection. It could very well be that lawyers who felt they had bad cases lowered their voices and spoke in a more aggressive tone to compensate.

In Gender, the Perception of Aggression, and the Overestimation of Gender Bias (Stewart-Williams, 2002), participants were presented hypothetical situations with male and female aggressors. Data did not support the hypothesis that because of gender stereotypes, people would perceive more aggression in men's than women's aggression; instead, women's aggression was rated as more acceptable than men's aggression.

The authors of I Don't Like the Cut of your Jib: Perceived Facial Masculinity as a Cue to Criminality (Estrada-Reynolds et al., 2017) stated:

Suspect masculinity and type of crime were manipulated to determine whether the degree of masculinity influenced whether participants believed they had committed the crime. Results showed that participants consistently associated masculinity with committing violent crime and showed some evidence for the general criminality hypothesis on secondary measures. These findings have important implications regarding law enforcement, eyewitness and juror bias, and legal decisions.

In ‘Lucky Boy!’; Public Perceptions of Child Sexual Offending Committed by Women (Bradbury & Martellozzo, 2021) the authors studied "1,651 comments made by the general public to nine Daily Mail online newspaper articles published from 2018 to 2019, reporting the sentencing decisions of female sex offenders, who have been charged and found guilty with the offense of sexual activity with a child". This study, unlike previous ones, "cross-examine[d] public responses to different typologies of offending behavior [such as] teachers, mothers, same sex offenders, co-offenders and finally those who offended for financial gain". The authors conclude:

[W]hile people demand equal sentencing decisions between male and female child sex offenders, this is limited by public perception when the abuser is an attractive female and, as a result, perceived as less harmful to the child, who is not seen no longer as a victim but as a ‘Lucky Boy’. Such preconceptions fuel shame, social stigma and stereotyping towards sexual exposure and prevents victims to disclose their abuse and achieve closure and justice.

According to The Gender Gap in Sex Offender Punishment (Shields & Cochran, 2019), women who commit sexual offenses are treated more leniently than their male counterparts. Male sex offenders were more substantially more likely to be sentenced to prison (47% vs 33%) and given longer terms than female sex offenders (on average more than 20 months longer), and these findings are similar across offense severity and whether or not the victim was a minor. Male sex offenders, all else equal, were perceived as more dangerous and culpable than female sex offenders. Unfortunately, the same study makes excuses for female offenders, speculating that male offenders cannot be treated outside of prison and female offenders cannot be treated inside prison.

The author of "Off with His __": Analyzing the Sex Disparity in Chemical Castration Sentences (Oswald, 2013) argues that "the punishment of chemical castration is, in effect, reserved exclusively for use against male offenders" and that "systemic problems plague the chemical castration sentencing regime". First and foremost, while chemical castration induces sterility in both male and female sex offenders, it is mostly only effective against male offenders to reduce recidivism (although this too "depends on the attributes of the particular convict"). The author explains that the belief that punishing heinous criminal offenders in an effective and appropriate manner through chemical castration was a laudable purpose, this was not based on rational policy considerations but instead are a result of "the general public becoming enthralled with the idea that modern medicine could provide a 'magic cure'" and that these laws "coincided trend toward more severe sentencing [which] is probably influenced by the media's method of reporting" as well as by the call for law and order that has underlined the campaign rhetoric of some candidates for political office". He goes on to lay out the problems with this. The first reason is the biased "statutes themselves and judicial interpretation of legislative intent [through which the] legislative branch's actions have created a nearly complete statutory bar against women being sentenced to chemical castration, even when they engage in the exact same conduct as men. He laments that "[m]ost shocking of all, perhaps, is the sheer number of examples of such discriminatory statutes, both facially and as applied". Second, men are sentenced more to crimes in general; this is partially because men do in fact commit more crimes, but as the author goes on to explain, "it may also be due, in part, to 'possible discrimination in the police officer's decision to arrest" and third, "[e]ven [women] do commit a sex crime [they] receive more lenient treatment [so that] if a woman committed a specified crime that made her eligible for chemical castration, she would have a much better chance of having her case dismissed or not being convicted than would her male counterpart". Fourth, he states that "vast judicial discretion in the chemical castration sentencing system provides a breeding ground for discrimination". And fifth, Depo-Provera (the drug used to achieve chemical castration which was originally created as a form of female birth control), is only effective at reducing recidivism in men. He concludes that "these actions make the likelihood of a woman being subjected to chemical castration virtually nonexistent", and that "[this] result cannot stand in a society that finds it inherently unjust to sentence offenders differently because of their sex". He proposes (A) to declare chemical castration statutes unconstitutional, (B) to encourage sentencing judges to refrain from sentencing any convict to chemical castration and (C) gives suggestions for reducing the sex disparity in the current castration sentencing regime. Additionally, the paper summarizes the status of chemical castration as a form of punishment in the U.S. and worldwide; I have copied the relevant passages here:

Chemical castration laws in the United States Chemical castration has gained increasing popularity within the United States. Although surgical castration has been performed on prisoners in the United States as early as 1899, California was the first state to enact chemical castration legislation, almost one hundred years later, on September 17, 1996. Now, several states, including California, Montana,"' Florida, Louisiana, Iowa, and Wisconsin "allow a judge to force a sex offender to undergo chemical castration." Although Georgia and Oregon once allowed chemical castration, these laws have since been repealed. Uniquely, Texas "gives the offender the decision to undergo voluntary surgical castration as a condition of release [but] does not [make the same] offer [for] chemical castration." Chemical castration legislation has been proposed but not yet adopted in Pennsylvania (1997), Oklahoma (2002),' Minnesota (2005), Vermont (2008), Alabama (2009), and Virginia (2011). This amounts to a total of at least sixteen states that have either proposed or adopted some type of chemical castration statute.

Chemical castration laws around the world The increasing popularity of chemical castration legislation around the world is likely to normalize these sentences in the United States, despite the sentencing regime's flaws. Although many European countries, including Denmark, Finland, Germany, Norway, and Sweden, have only enacted castration laws as treatment or punishment of sex offenders, Poland was the first country in the European Union to impose chemical castration as a form of punishment, in 2010. However, support for chemical castration is not limited to Europe. For example, the Australian Minister for Police and Emergency Services has advocated for compulsory chemical castration of child molesters and rapists. Similar legislation has been proposed in New Zealand. Russia also recently enacted a law authorizing the use of chemical castration on child sex offenders. Likewise, chemical castration laws have been enacted or proposed in non-Western societies (as recently as this year) in countries such as Taiwan and Turkey. Furthermore, an Indian judge recently "caused a storm . . . when she suggested castration as the most appropriate punishment for pedophiles and serial sex offenders."

The author of Gender-Specific Differences in Corporal Punishment and Children’s Perceptions of Their Mothers’ and Fathers’ Parenting (Mehlhausen-Hassoen, 2019) states:

This study also examined whether gender interactions influence the relationship between corporal punishment and respondents’ perceptions of their parents’ behavior, namely the perceived parenting the respondents received during childhood. Cross tabulations and repeated measures were used to analyze the data. Significantly fewer daughters (as compared with sons) experienced corporal punishment and significantly fewer daughters experienced corporal punishment from both parents. Corporal punishment had a significant negative impact on the perceived parent–child relationship. Violent parental behavior had a significantly stronger effect on the perception of the father–child relationship, as compared with the perception of the mother–child relationship, even when the mother was the violent parent. These findings point to the importance of gender interactions in research and psychosocial practice.

The study named Corporal punishment and physical maltreatment against children: A community study on Chinese parents in Hong Kong (Tang, 2006) "aimed to examine rates and associated factors of parent-to-child corporal punishment and physical maltreatment in Hong Kong Chinese families". They found that "[m]others as compared to fathers reported higher rates and more frequent use of corporal punishment on their children, but this parental gender effect was insignificant among older parents and those with adolescent children" and that "[b]oys as compared to girls were more likely to experience higher rates and more frequent parental corporal punishment, especially in middle childhood at aged 5-12". Children's young age, male gender, and externalizing behaviors as well as parents' young age, non-employment, and marital dissatisfaction were shown to be significant correlates of parental corporal punishment.