Discriminating between sick and healthy faces based on early sickness cues: an exploratory analysis of sex differences

Background and objectives

It has been argued that sex and disease-related traits should influence how observers respond to sensory sickness cues. In fact, there is evidence that humans can detect sensory cues related to infection in others, but lack of power from earlier studies prevents any firm conclusion regarding whether perception of sickness cues is associated with sex and disease-related personality traits. Here, we tested whether women (relative to men), individuals with poorer self-reported health, and who are more sensitive to disgust, vulnerable to disease, and concerned about their health, overestimate the presence of, and/or are better at detecting sickness cues.

Methodology

In a large online study, 343 women and 340 men were instructed to identify the sick faces from a series of sick and healthy photographs of volunteers with an induced acute experimental inflammation. Participants also completed several disease-related questionnaires.

Results

While both men and women could discriminate between sick and healthy individuals above chance level, exploratory analyses revealed that women outperformed men in accuracy and speed of discrimination. Furthermore, we demonstrated that higher disgust sensitivity to body odors is associated with a more liberal decision criterion for categorizing faces as sick.

Conclusion

Our findings give strong support for the human ability to discriminate between sick and healthy individuals based on early facial cues of sickness and suggest that women are significantly, although only slightly, better at this task. If this finding is replicated, future studies should determine whether women's better performance is related to increased avoidance of sick individuals.

Comparable responses to a wide range of olfactory stimulation in women and men

The evidence for differences between women and men in terms of olfactory abilities is contradictory. We analyzed women and men's performance and reactions to a wider range of odour exposure outcomes than usually studied, to assess possible differences and similarities between sexes. Measures of sensitivity and sensory decision rule were established in 37 women and 39 men. Perceptual, cognitive, symptom-related and autonomic nervous system (skin conductance level and heart-rate variability) reactions were also assessed during extended ambient odour exposure, as well as participants' self-rated chemical intolerance. Bayesian analyses consistently revealed greater support for sex-related similarities than differences, suggesting that women and men perform and react comparably not only in terms of basic olfactory measures, but also to environmental odour exposure mimicking everyday situations.

Humans can detect axillary odor cues of an acute respiratory infection in others

Background and objectives

Body odor conveys information about health status to conspecifics and influences approach-avoidance behaviors in animals. Experiments that induce sickness in otherwise healthy individuals suggest that humans too can detect sensory cues to infection in others. Here, we investigated whether individuals could detect through smell a naturally occurring acute respiratory infection in others and whether sickness severity, measured via body temperature and sickness symptoms, was associated with the accuracy of detection.

Methodology

Body odor samples were collected from 20 donors, once while healthy and once while sick with an acute respiratory infection. Using a double-blind, two-alternative forced-choice method, 80 raters were instructed to identify the sick body odor from paired sick and healthy samples (i.e. 20 pairs).

Results

Sickness detection was significantly above chance, although the magnitude of the effect was low (56.7%). Raters' sex and disgust sensitivity were not associated with the accuracy of sickness detection. However, we find some indication that greater change in donor body temperature, but not sickness symptoms, between sick and healthy conditions improved sickness detection accuracy.

Conclusion and implications

Our findings suggest that humans can detect individuals with an acute respiratory infection through smell, albeit only slightly better than chance. Humans, similar to other animals, are likely able to use sickness odor cues to guide adaptive behaviors that decrease the risk of contagion, such as social avoidance. Further studies should determine how well humans can detect specific infections through body odor, such as Covid-19, and how multisensory cues to infection are used simultaneously.

Educational inequalities in hypothermia mortality in the Baltic countries and Finland in 2000-15

BACKGROUND

Despite an increased focus on cold-related mortality in recent years, there has been comparatively little research specifically on hypothermia mortality and its associated factors.

METHODS

Educational inequalities in hypothermia mortality among individuals aged 30-74 in the Baltic countries (Estonia, Latvia, Lithuania) and Finland in 2000-15 were examined using data from longitudinal mortality follow-up studies of population censuses (the Baltics) and from a longitudinal register-based population data file (Finland).

RESULTS

Age-standardized mortality rates (ASMRs) were much higher in the Baltic countries than in Finland across the study period. From 2000-07 to 2008-15, overall ASMRs declined in all countries except among Finnish women. Although a strong educational gradient was observed in hypothermia mortality in all countries in 2000-07, inequalities were larger in the Baltic countries. Between 2000-07 and 2008-15, ASMRs declined in all educational groups except for high-educated women in Finland and low-educated women in Lithuania; the changes however were not always statistically significant. The absolute mortality decline was often larger among the low educated resulting in narrowing absolute inequalities (excepting Lithuania), whereas a larger relative decline among the high educated (excepting Finnish women) resulted in a considerable widening of relative inequalities in hypothermia mortality by 2008-15.

CONCLUSION

Although some reduction was observed in absolute educational inequalities in hypothermia mortality in 2000-15, substantial and widening relative inequalities highlight the need for further action in combatting factors behind deaths from excessive cold in socioeconomically disadvantaged groups, including risky alcohol consumption and homelessness.

A Bayesian semiparametric approach for inference on the population partly conditional mean from longitudinal data with dropout

Studies of memory trajectories using longitudinal data often result in highly nonrepresentative samples due to selective study enrollment and attrition. An additional bias comes from practice effects that result in improved or maintained performance due to familiarity with test content or context. These challenges may bias study findings and severely distort the ability to generalize to the target population. In this study, we propose an approach for estimating the finite population mean of a longitudinal outcome conditioning on being alive at a specific time point. We develop a flexible Bayesian semiparametric predictive estimator for population inference when longitudinal auxiliary information is known for the target population. We evaluate the sensitivity of the results to untestable assumptions and further compare our approach to other methods used for population inference in a simulation study. The proposed approach is motivated by 15-year longitudinal data from the Betula longitudinal cohort study. We apply our approach to estimate lifespan trajectories in episodic memory, with the aim to generalize findings to a target population.

No Evidence That Hormonal Contraceptives Affect Chemosensory Perception

The use of oral contraceptives (OC) in the form of a hormonal pill has been widespread for decades. Despite its popularity and long-time use, there is still much ambiguity and anecdotal reports about a range of potential side effects. Here, we addressed the potential effect of OC use on chemosensory perception. Previous research has almost exclusively focused on olfaction, but we expanded this to the trigeminal system and the sense of taste. We used Bayesian statistics to compare the olfactory, trigeminal, and taste detection abilities between a group of 34 normal cycling women and a group of 26 women using OC. Our results indicated that odor, trigeminal, and taste thresholds were not affected by the use of OC. Moreover, neither odor perception, nor taste perception was affected; all with Bayes factors consistently favoring the null hypothesis. The only exception to these results was odor identification where Bayes factors indicated inconclusive evidence. We conclude that effects of OC use on chemosensory perception are unlikely, and if present, likely are of no to little behavioral relevance.

Internet-delivered psychological treatments: from innovation to implementation

Internet interventions, and in particular Internet-delivered cognitive behaviour therapy (ICBT), have existed for at least 20 years. Here we review the treatment approach and the evidence base, arguing that ICBT can be viewed as a vehicle for innovation. ICBT has been developed and tested for several psychiatric and somatic conditions, and direct comparative studies suggest that therapist-guided ICBT is more effective than a waiting list for anxiety disorders and depression, and tends to be as effective as face-to-face CBT. Studies on the possible harmful effects of ICBT are also reviewed: a significant minority of people do experience negative effects, although rates of deterioration appear similar to those reported for face-to-face treatments and lower than for control conditions. We further review studies on change mechanisms and conclude that few, if any, consistent moderators and mediators of change have been identified. A recent trend to focus on knowledge acquisition is considered, and a discussion on the possibilities and hurdles of implementing ICBT is presented. The latter includes findings suggesting that attitudes toward ICBT may not be as positive as when using modern information technology as an adjunct to face-to-face therapy (i.e., blended treatment). Finally, we discuss future directions, including the role played by technology and machine learning, blended treatment, adaptation of treatment for minorities and non-Western settings, other therapeutic approaches than ICBT (including Internet-delivered psychodynamic and interpersonal psychotherapy as well as acceptance and commitment therapy), emerging regulations, and the importance of reporting failed trials.