Introduction
Trust has been the grease in the wheels of historical and modern societies. Trust promotes economic growth, organizational efficiency, and innovation. The level of trust depends on beliefs about trustworthiness–individuals trust more if they believe their counterpart is trustworthy (Fehr, 2009). If individuals expect not to be cheated on and act accordingly, trading partners, acquaintances, or strangers can transact more smoothly with each other without the need of an explicit enforcement mechanism for every single contract.
The origins of trust can be investigated from several perspectives. One perspective is the environment an individual is exposed to. Environmental factors contributing to the choice of whether to trust include experiences (Nunn and Wantchekon, 2011; Stevenson and Wolfers, 2011; Peysakhovich and Rand, 2016), culture (Guiso et al., 2009; Bohnet et al., 2010), institutions (Algan and Cahuc, 2010; Alesina and Zhuravskaya, 2011), and even physical appearance (Duarte et al., 2012). The environment and individual lives in, and the clues on the trustworthiness of others she picks up, are important determinants of trust.
While determinants of trust can be attributed to the environment an individual is exposed to, biology provides another perspective. Trust and trustworthiness both have a genetic component (Cesarini et al., 2008; Riedl and Javor, 2012), they are affected by hormones (Kosfeld et al., 2005; Zak et al., 2005), and can be traced to distinct brain areas in functional magnetic resonance imaging (fMRI) representing fear of deception, anticipation of long-term benefits, mentalizing and rewarding experiences of being trusted (Rilling and Sanfey, 2011).
An important everyday biological process, hunger, has been until now virtually ignored in research for trust and reciprocity. However, empirical evidence on visceral factors mitigating or inhibiting trust is so far limited to physical temperature and sleep deprivation. Higher temperature has been associated with increased trust in others and prosociality in some studies (Williams and Bargh, 2008; Kang et al., 2011; although the results of the former study failed to replicate in Lynott et al., 2014). In contrast, after 36-h total sleep deprivation individual are less likely to place trust on others (Anderson and Dickinson, 2010; Dickinson and McElroy, 2017).
We contribute to this limited body of knowledge on the role of visceral factors in decision making by investigating how trust and trustworthiness are influenced by an everyday visceral factor, short-term hunger1. We concentrate on short-term hunger in this study since it is societally important: most individuals experience it every day. Furthermore, short-term hunger is generally not considered an issue that needs to be urgently addressed. To our knowledge, we are the first to empirically investigate whether short-term hunger influences trust and trustworthiness.
Trust is highly context-dependent and varies between countries, ethnicities, and institutions individuals are exposed to (Fehr, 2009). According to the social heuristics hypothesis (SHH, first version in Rand et al., 2012), beneficial social behaviors become internalized as default heuristics that impact and guide behavior reasonably automatically (Rand et al., 2014; Peysakhovich and Rand, 2016). Trusting in a high trust society can for instance be the intuitive behavioral response. In this paper, we particularly concentrate on short-term hunger in a high-trust society. Finland, where our data originate from, consistently ranks very high in interpersonal trust according to the World Values Survey placing third in the fifth wave of the survey.
To study whether short-term hunger influences trust and trustworthiness we observe choice behavior in a laboratory. Similar to recent work in social sciences (see Coleman, 1990; Fehr, 2009), we collect data on trust and trustworthiness behavior using the trust game (Berg et al., 1995) and by observing whether an individual leaves belongings in an unlocked and unsupervised laboratory room. In the laboratory, we compare decisions by sated healthy Finnish subjects after consuming breakfast with decisions by subjects consuming only water.
We offer two contributions to the literature. First, this study is the first that links short-term hunger with trusting and reciprocal behavior. While low blood glucose levels or short-term hunger have been previously linked in resource depletion models with decisions requiring self-control (Gailliot and Baumeister, 2007; Kuhn et al., 2017), risk taking (Symmonds et al., 2010; de Ridder et al., 2014), intertemporal choice (Wang and Dvorak, 2010), and political views (Petersen et al., 2014), scholars have not yet linked short-term hunger with individual trust and trustworthiness. Second, although we fail to reject the null hypothesis of no effect, the results would not be inconsistent with the claim that hunger leads to more trusting and strategic behavior. The literature so far generally associates low blood glucose levels or short-term hunger with heightened greed (e.g., Briers et al., 2006; Gailliot and Baumeister, 2007), but recent evidence (de Ridder et al., 2014) also indicates that hungry individuals may be more capable of making strategic decisions. This is consistent with the notion from the recent literature pointing out that decision environment may have unanticipated effect direction and mechanism than suggested by the resource depletion models (Kuhn et al., 2017).
This paper proceeds as follows. In the next section, we introduce hypotheses for trust and trustworthiness. Section “Short-Term Hunger, Trustworthiness, and Trust in the Laboratory” presents results from an empirical study and Section “Conclusion” concludes.
Development of Hypotheses
Trusting and reciprocating by being trustworthy are intertwined and correlated with cooperative behavior in general, such as altruism and cooperation in the public good game (PGG; Peysakhovich et al., 2014). In an environment in which agents are trustworthy and are expected to reciprocate, trustworthiness promotes a cycle of mutual trust. However, trust and trustworthiness have important conceptual differences. Trusting is an act of the sender voluntarily placing resources at the disposal of the trustee without any legal commitment from the latter (some authors dub as “strategic cooperation”, see e.g., Rand, 2016). The act of trust is generally associated with an expectation that the act will pay off in terms of the investor’s goals (Fehr, 2009), although this notion has been challenged in the more recent literature (Espín et al., 2016). In a one-shot game, trusting behavior may be regarded as self-interested, strategic behavior if the opponent reciprocates with high enough of a probability of making the investment worthwhile (Bohnet and Zeckhauser, 2004). In contrast, returning a favor by being a trustworthy second mover in a one-shot trust game is prosocial behavior through an act of positive reciprocity and cannot be explained by purely selfish motives (Sanfey, 2007; dubbed as “pure cooperation” in Rand, 2016). As a result, we also use the terms trustworthiness and reciprocity interchangeably.
Drawing from previous literature, it is possible to posit two opposite predictions on the relationship between short-term hunger, trust, and trustworthiness. Based on recent controversies in the literature, it is also possible that short-term hunger has no impact on trust or trustworthiness, or that results may be highly context-dependent. We discuss all these possibilities below.
Hunger Increases Trust and Trustworthiness (H<sub><italic>A</italic>1</sub>)
Since deviation from an intuitive choice requires energy and behavioral control (Fairclough and Houston, 2004), we construct our first alternative hypothesis by considering trusting and trustworthiness as automated behavior. We argue that if an individual experiences short-term hunger, he or she would be more inclined to use less cognitive control and rely on the automated behaviors.
Some of the recent developments [described in Zaki and Mitchell (2013); also referred to as social heuristics hypothesis, or SHH, by Rand et al. (2013, 2014), Rand (2016), formalized in Bear and Rand (2016) and Bear et al. (2017)] on prosociality suggest that prosocial behaviors are automated and intuitive, although not always for all people. Individuals act more prosocially in experiments priming for the use of intuitive reasoning through time pressure and constrained ability to exert control. Bear and Rand (2016) as well as Bear et al. (2017) formalize this argument in their models by setting a cost, d, of exerting deliberation over intuition. Deliberation only pays off if the benefits of deliberation exceed a threshold T. Hence, as long as payoffs are small and costs of cognitive processing exceed potential gains, individuals cooperate intuitively if they come from an environment where cooperation is an equilibrium strategy. In addition, the argument by Rand (2016) would strengthen the expectation of observing increasing trust and trustworthiness in hungry individuals. Trusting involves future consequences and thus an impairment of cognitive processing such as induction of short-term hunger should increase trust and trustworthiness.
Preference for prosociality and fair sharing of resources may extend to the behavior of non-human primates (Brosnan and de Waal, 2003; former study contested in Roma et al., 2006) and the presence of other humans or human like features such as eyes accentuates prosociality in choices even in the absence of reciprocal social gratification (Burnham and Hare, 2007). These findings also corroborate the argument of prosocial and reciprocal behavior as intuitive, automated behavior. If short-term hunger induces individuals in the laboratory to resort to the automated behavior, they may be intuitively inclined to trust and reciprocate more than sated individuals who have more energy reserves to engage in controlled and effortful processes.
Recent developments in SHH (Rand, 2016) have made a distinction between strategic (such as trusting) and pure (such as reciprocating) cooperation. This line of thought argues that for strategic cooperation, inducing cognitive impairment would not have an impact as for pure cooperation. We would hence expect a stronger impact on trustworthiness than trust (if any) in the laboratory, because trusting induces no cognitive conflict if trusting is purely strategic behavior. However, there still may be a positive impact on trust, especially if relying on the early, more broad version of SHH (Rand et al., 2012) which does not incorporate cognitive conflict. In addition, trusting may be strategic, but it does no have to be strategic for all individuals.
Hunger Decreases Trust and Trustworthiness (H<sub><italic>A</italic>2</sub>)
It is possible to argue that hunger decreases trust and trustworthiness using three different lines of thought in our second alternative hypothesis. The first line of thought would use similar argumentation as above but with the opposite conclusion: not trusting or reciprocating is the default response and cognitive impairment such as short-term hunger would tilt toward less trusting and reciprocating behavior. The second line of thought draws from literature associating low blood glucose with heightened greed and impulsiveness. The third line of thought comes from evolutionary psychology.
Some scholars argue that prosocial behaviors are not automatic but trusting and reciprocating require cognitive effort. The proponents of the reflective model (e.g., Moore and Loewenstein, 2004; DeWall et al., 2008; Steinbeis et al., 2012; defined in Zaki and Mitchell, 2013) argue that humans act prosocially by suppressing the urge to act selfishly. This suppression requires energy and hence hungry individuals with reduced energy levels would be less likely to act prosocially. The expectation that not trusting is the default choice stems for instance from the literature on human development which suggests that not trusting others is the hard-wired standard response present in childhood. This tendency diminishes with experience: trusting behavior increases throughout childhood, and remains at a reasonably steady level in adulthood (Sutter and Kocher, 2007; van den Bos et al., 2010). Rand et al. (2014) make a related argument in laboratory: individuals with more laboratory experience cooperate less in one-shot experiments. This suggests that even if trusting and reciprocity are default choices at birth, individuals may update their priors based on experience and not trust and reciprocate as a default.
Low blood glucose levels have been associated with heightened greed, such as decreased self-control, impulse inhibition, and greater discounting of the future (e.g., Briers et al., 2006; Muraven et al., 2006; Gailliot et al., 2007; Hagger et al., 2010; Symmonds et al., 2010; Wang and Dvorak, 2010). Heightened greed and decreased self-control thus leave more room for selfish urges when individuals are hungry.
Some authors arrive at the same conclusion using argumentation from evolutionary psychology. Low blood glucose levels are linked to changes in behavior consistent with promoting strategies fit for survival. Increased risk-taking (Symmonds et al., 2010; Wang and Dvorak, 2010) and more impulsive behavior driven by lower self-control (e.g., Read and van Leeuwen, 1998; Gailliot and Baumeister, 2007) have been linked to depletion of energy resources in the body to promote more aggressive and risk-taking foraging strategies. Even the classic Maslow (1943) need hierarchy model would indicate that individuals subject to primary physiological needs such as hunger would prioritize immediate food acquisition (1st level of the hierarchy) to more future-oriented reciprocal behavior (2nd level in the need hierarchy) requiring self-control and risk-tolerance.
In conclusion, from these three arguments we could posit that increasing short-term hunger would lead to decreased trust and trustworthiness.
Hunger Changes Trust and Trustworthiness Depending on Context (H<sub><italic>A</italic>3</sub>)
Based on the discussion above, it is possible to posit trusting and trustworthiness either as automated or controlled process. This discrepancy could be explained by the fact that trust is highly context-dependent and varies between countries, ethnicities, and institutions individuals are exposed to (Fehr, 2009). Another argument leading to same conclusion leans on different types of social cooperation. A recent meta study by Rand (2016) argues that for pure cooperation, such as reciprocation in the trust game, deliberation reduces cooperation. Hence, cooperation with few future consequences (such as being the receiver in a one shot trust game) of one’s actions would be impaired by manipulation increasing the cost of cognitive processing.
Our experiments take place in Finland, which is a high-trust society. It consistently ranks very high in interpersonal trust according to the World Values Survey placing third in the fifth wave of the survey. Trusting and reciprocating with a stranger is the social norm in Finland similar to other Nordic countries (Brandt and Svendsen, 2010). According to the SHH (Rand et al., 2014; Peysakhovich and Rand, 2016), we would expect hungry individuals to trust and reciprocate with their counterparts more in the laboratory. This is because the society reinforce trusting behavior strongly so that trust and reciprocating have evolved to be intuitive choices and also a strategically sound decisions in our participant pool.
Hunger Has No Impact on Trust and Trustworthiness (H<sub><italic>Null</italic></sub>)
It is also entirely possible that short-term hunger manipulation does not change trusting and reciprocal behavior. This is the case if (a) there is no generalizable baseline in prosocial behavior (individuals have no default in trusting and reciprocating behavior) which would be influenced by cognitive load manipulation (such as short-term hunger manipulation), (b) short-term hunger manipulation has no impact on trust and trustworthiness, or a combination of (a) and (b).
For (a), the jury is still out as the literature on SHH is currently under controversy. Tinghög et al. (2013) fail to replicate the highly influential original study on SHH by Rand et al. (2012) reporting individuals who reach decisions faster to be more cooperative and thus predisposed to cooperation. Verkoeijen and Bouwmeester (2014) report evidence inconsistent with the SHH. Furthermore, Bouwmeester et al. (2017) also fail to replicate the Rand et al. (2012) result in a multilab setting.
For (b), scholars have recently proposed that blood glucose levels may not have an impact on behavior. Resource depletion through lower blood glucose level may not lead to lower self-control and thus more likely default response. Vadillo et al. (2016) challenge earlier studies linking glucose and self-control and present evidence on publication bias in this stream of literature. Lange and Eggert (2014) do not find evidence on lower glucose having a detrimental impact on self-control. Furthermore, Kurzban (2010) dissects the theoretical argumentation of the glucose model concluding that empirical evidence consistent with glucose not being a resource to willpower, but may be an input to the decision-making process. Some studies using cognitive load manipulation other than glucose report findings consistent with the idea that prosocial behavior is not influenced by cognitive load (Kessler and Meier, 2014; Mieth et al., 2016). On a higher conceptual level, these findings together with failed replications (Hagger et al., 2016) challenge the ego depletion model of self-control (Baumeister et al., 1998; Muraven et al., 1998).
In sum, the recently accumulated evidence on (a) and (b) cast doubt on the social heuristics hypothesis, at least in its original form (Rand et al., 2012) and the glucose model of self- control. Hence, based on the previous literature, it is also entirely possible that cognitive load manipulation through short-term hunger does not have an impact on trust and trustworthiness.