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Different professionals (e.g. in the military) have to perform cognitive challenging tasks in multi-stressor environments. However, our understanding how combined stressors interact and affect cognitive performance is limited (Van Dongen & Belenky, 2009). This study examined how sleep deprivation (SD) and acute social stress affect cognitive performance in isolation and in combination, and used a comprehensive approach to find evidence for a (shared) mechanism. Recent research suggests that SD leads to higher amounts of proinflammatory markers (i.e. cytokines) in the blood, which assumedly contribute to a decline in cognitive performance (Irwin, 2019; Shields et al., 2017). In addition, acute social stressors have also been shown to elicit an immune response, as reflected by circulating cytokines in blood (Marsland et al., 2017; Prather et al., 2014). These findings suggest that different stressors may affect cognitive performance through an effect on the immune system. We therefore hypothesize that individuals showing a high proinflammatory response to a combination of two stressors (SD and acute social stress) are more vulnerable to cognitive decline compared to individuals showing a lower proinflammatory response. To test this hypothesis, we measured not only cognitive performance, but also the physiological response and biochemical determinants of metabolism and inflammation at baseline and after SD, but also in response to an acute social stressor (Tkacheenko & Dinges, 2018).

Monitoring an individual’s mental state using unobtrusively measured signals is regarded as an essential element in symbiotic human-machine systems. However, it is not straightforward to model the relation between mental state and such signals in real life, without resorting to (unnatural) emotion induction. We recorded heart rate, facial expression and computer activity of nineteen participants while working at the computer for ten days. In order to obtain ‘ground truth’ emotional state, participants indicated their current emotion using a valence-arousal affect grid every 15 min. We found associations between valence/arousal and the unobtrusively measured variables. There was some first success to predict subjective valence/arousal using personal classification models. Thus, real-life office emotions appear to vary enough, and can be reported well enough, to uncover relations with unobtrusively measured variables. This is required to be able to monitor individuals in real life more fine-grained than the frequency with which emotion is probed.

Interactions with others affect our mood, and vice versa. Unsurprisingly, people with a mood disorder such as depression often have difficulties in their social relationships. Depression is often thought to be associated with a decreased availability of serotonin, a signaling molecule in the brain which enables the processing of social and emotional information. Therefore a decreased availability of serotonin could also have an adverse effect on social behavior and mood during interactions with others. However, Hogenelst and colleagues showed that a temporary decrease of serotonin (over several hours) has little impact on mood or social behavior as measured in the lab. The results were similar in study participants with and without an elevated depression risk. In a second study in people with an elevated depression risk, the researchers increased the availability of serotonin over several days. They examined the effects on mood and social behavior in everyday life. As expected, mood improved. Unexpectedly, however, the participants also became less friendly. This behavioral effect was only seen during interactions at home. It is possible that, when serotonin availability was increased, participants stood up for themselves more. This in line with the idea that people prone to depression experience little control over their social lives. As most medications for depression aim to increase the availability of serotonin, an important next question is how these medications affect the social behavior of depressed people.