Introduction

Most people report wanting to be happy (Diener, 2000) – that is, to feel satisfied with their lives and to experience frequent positive emotions and infrequent negative emotions (Diener et al., 1999). A growing number of studies show that happiness correlates with, predicts, and causes many positive outcomes, including success in work (e.g., performance and salary), social relationships (e.g., number of friends and social support), and health and coping [e.g., physical symptoms and longevity (Prochaska et al., 2012)]; for reviews, see (Lyubomirsky et al., 2005; Diener et al., 2017; Walsh et al., 2018). Happy people also tend to show more positive perceptions of themselves and others, greater sociability and likability, more prosocial behavior, and superior creativity (Lyubomirsky et al., 2005).

According to Google Trends (Google Trends, 2019), searches for well-being have increased more than 500% since collection began in 2004. Given the clear benefits of happiness, it is unsurprising to see rising interest in personal well-being and methods to increase it. Literature in the growing area of well-being science points toward positive activity interventions (PAIs), such as writing letters of gratitude (e.g., Emmons and McCullough, 2003; Lyubomirsky et al., 2011), and practicing kindness (e.g., Dunn et al., 2008; Chancellor et al., 2018), as simple behavioral strategies to promote well-being, many of which have been empirically validated (Sin and Lyubomirsky, 2009; Bolier et al., 2013; Layous and Lyubomirsky, 2014). These PAIs have the potential to improve affect, and in turn, promote positive health and well-being outcomes without the use of drugs, costly or stigmatizing treatment, or significant behavioral changes. However, for such interventions to become useful and trusted tools for clinical or public use, the ability to detect their efficacy is critical.

The current state of the art measurement of happiness, and of PAI efficacy, is through self-report. However, self-report variables, even those with decent reliability and validity, are notoriously biased (Schwarz, 1999; Dunning et al., 2004), especially toward socially desirable responses (Velicer et al., 1992; Mezulis et al., 2004; Van De Mortel, 2008) – for example, toward appearing to be happier. Further, individual differences such as sex and culture serve as moderators or create additional variance (Lindsay and Widiger, 1995; Beaten et al., 2000). This has led researchers to search for “objective” measures of happiness that do not rely on self-report, like Facebook status updates (Chen et al., 2017) or Duchenne smiles (Harker and Keltner, 2001). Measures of physiology like electroencephalography (EEG) or heart rate monitoring, as well as cognitive tasks that tap into domains like memory, attention, and perception, are considered less biased by the social influences that plague self-report. Although these measures can be noisy, they are considered (by some) as more objective measures of underlying emotional and cognitive processes (Calvo and Mello, 2015).

Here we aimed to leverage recent advancements in low-cost, readily available physiological measurement devices and a large body of cognitive psychology research to determine the practical utility of cognitive and physiological measures in assessing the effects of a positive versus negative activity intervention. We aimed to verify whether these measures were indeed simple to implement, robust, and predictive for well-being research, thereby providing alternative measures to self-reported well-being levels.

In the current study, students were administered either a PAIs (writing about gratitude and recalling a kind act) or a negative activity intervention (writing about ingratitude and recalling an unkind act). Before and after the intervention, the participants completed both standard psychological measures of their current affective states, as well as several tasks designed to quantify the cognitive domains of memory, attention, and high-level perception. Additionally, physiological measurements of the central (EEG) and autonomic (heart rate, skin temperature, galvanic skin conductance) systems were recorded. This work builds upon our previous findings (Revord et al., 2019), which reported the self-report psychological outcomes of the same positive and negative activity interventions.