People often predict that they, and others, will be biased by sunk costs—they think that investing in an object or goal increases how much one values or wants it. In this article, we use sunk cost predictions to look at people’s theory of mind and their conceptions of mental life. More specifically, we ask which mental states and motivations are seen as underlying the bias. To investigate this, participants in two preregistered experiments predicted whether different kinds of agents would be biased by sunk costs, and also assessed the agents’ mental abilities. Participants predicted that some kinds of agents (e.g., human adults and children, robots) would show the sunk cost bias and that others would not (e.g., raccoons and human babies). These predictions were strongly related to the participants’ assessments of whether the different kinds of agents are capable of seeing actions as wasteful, but also related to their assessments of the agents’ capacities to feel regret and frustration.

Boyer proposes that ownership intuitions depend on tracking cues predictive of agents’ motivations to compete for resources. However, the account may mis-predict people's intuitions about ownership, and it may also be too cognitively costly to be feasible. Even so, alternative accounts could benefit by taking inspiration from how the account handles thorny issues in the psychology of ownership.

The target article proposes that people perceive social robots as depictions rather than as genuine social agents. We suggest that people might instead view social robots as social agents, albeit agents with more restricted capacities and moral rights than humans. We discuss why social robots, unlike other kinds of depictions, present a special challenge for testing the depiction hypothesis.

We investigated whether the personal importance of objects influences utilitarian decision-making in which damaging property is necessary to produce an overall positive outcome. In Experiment 1, participants judged saving five objects by destroying a sixth object to be less acceptable when the action required destroying the sixth object directly (rather than as a side-effect) and the objects were personally important (rather than unimportant). In Experiment 2, we demonstrated that utilitarian judgments were not influenced by the objects’ monetary worth. Together these findings suggest that personal importance underlies people’s sensitivity to damaging property as a means for utilitarian gains.

For connoisseurs of antiques and antiquities, cleaning old objects can reduce their value. In five experiments (total N = 1,019), we show that lay people also often judge that old objects are worth less when cleaned, and we test two explanations for why cleaning can reduce object value. In Experiment 1, participants judged that cleaning an old object would reduce its value, but judged that cleaning would not reduce the value of an object made from a rare material. In Experiments 2 and 3 we described the nature, age and origin of the traces that cleaning would remove. Now participants judged that cleaning old historical traces would reduce the object’s value, but cleaning recently acquired traces would not. In Experiment 4, participants judged that the current value of an old object is reduced even when it was cleaned in ancient times. However, participants in Experiment 5 valued objects cleaned in ancient times as much as uncleaned ones, while judging that objects cleaned recently are worth less. Together, our findings suggest that cleaning objects may reduce value by removing valued historical traces, and by changing objects from their historic state. We also outline potential implications for previous studies showing that cleaning reduces the value of objects used by admired celebrities.

When people have invested resources into an endeavor, they typically persist in it, even when it becomes obvious that it will fail. Here we show this bias extends to people’s moral decision-making. Across two preregistered experiments (N = 1592) we show that people are more willing to proceed with a futile, immoral action when costs have been sunk (Experiment 1A and 1B). Moreover, we show that sunk costs distort people’s perception of morality by increasing how acceptable they find actions that have received past investment (Experiment 2). We find these results in contexts where continuing would lead to no obvious benefit and only further harm. We also find initial evidence that the bias has a larger impact on judgment in immoral compared to non-moral contexts. Our findings illustrate a novel way that the past can affect moral judgment. Implications for rational moral judgment and models of moral cognition are discussed.

In considering moral dilemmas, people often judge the acceptability of exchanging individuals’ interests, rights, and even lives. Here we investigate the related, but often overlooked, question of how people decide who to sacrifice in a moral dilemma. In three experiments (total N = 558), we provide evidence that these decisions often depend on the feeling that certain people are fungible and interchangeable with one another, and that one factor that leads people to be viewed this way is shared nationality. In Experiments 1 and 2, participants read vignettes in which three individuals’ lives could be saved by sacrificing another person. When the individuals were characterized by their nationalities, participants chose to save the three endangered people by sacrificing someone who shared their nationality, rather than sacrificing someone from a different nationality. Participants do not show similar preferences, though, when individuals were characterized by their age or month of birth. In Experiment 3, we replicated the effect of nationality on participant’s decisions about who to sacrifice, and also found that they did not show a comparable preference in a closely matched vignette in which lives were not exchanged. This suggests that the effect of nationality on decisions of who to sacrifice may be specific to judgments about exchanges of lives.

Machines are increasingly used to make decisions. We investigated people’sbeliefs about how they do so. In six experiments, participants (totalN = 2664) predicted how computer and human judges woulddecide legal cases on the basis of limited evidence — eitherindividuating information from witness testimony or base-rate information. InExperiments 1 to 4, participants predicted that computer judges would be morelikely than human ones to reach a guilty verdict, regardless of which kind ofevidence was available. Besides asking about punishment, Experiment 5 alsoincluded conditions where the judge had to decide whether to reward suspectedhelpful behavior. Participants again predicted that computer judges would bemore likely than human judges to decide based on the available evidence, butalso predicted that computer judges would be relatively more punitive than humanones. Also, whereas participants predicted the human judge would give moreweight to individuating than base-rate evidence, they expected the computerjudge to be insensitive to the distinction between these kinds of evidence.Finally, Experiment 6 replicated the finding that people expect greatersensitivity to the distinction between individuating and base-rate informationfrom humans than computers, but found that the use of cartoon images, as in thefirst four studies, prevented this effect. Overall, the findings suggest peopleexpect machines to differ from humans in how they weigh different kinds ofinformation when deciding.

This response argues that when you represent others as knowing something, you represent their mind as being related to the actual world. This feature of knowledge explains the limits of knowledge attribution, how knowledge differs from belief, and why knowledge underwrites learning from others. We hope this vision for how knowledge works spurs a new era in theory of mind research.

Research on the capacity to understand others' minds has tended to focus on representations of beliefs, which are widely taken to be among the most central and basic theory of mind representations. Representations of knowledge, by contrast, have received comparatively little attention and have often been understood as depending on prior representations of belief. After all, how could one represent someone as knowing something if one does not even represent them as believing it? Drawing on a wide range of methods across cognitive science, we ask whether belief or knowledge is the more basic kind of representation. The evidence indicates that nonhuman primates attribute knowledge but not belief, that knowledge representations arise earlier in human development than belief representations, that the capacity to represent knowledge may remain intact in patient populations even when belief representation is disrupted, that knowledge (but not belief) attributions are likely automatic, and that explicit knowledge attributions are made more quickly than equivalent belief attributions. Critically, the theory of mind representations uncovered by these various methods exhibits a set of signature features clearly indicative of knowledge: they are not modality-specific, they are factive, they are not just true belief, and they allow for representations of egocentric ignorance. We argue that these signature features elucidate the primary function of knowledge representation: facilitating learning from others about the external world. This suggests a new way of understanding theory of mind – one that is focused on understanding others' minds in relation to the actual world, rather than independent from it.

Hoerl & McCormack suggest that saving tools does not require temporal reasoning. However, we identify a class of objects that are only possessed (i.e., saved) in anticipation of future needs. We propose that investigating these future-oriented objects may help identify temporal reasoning in populations where this ability is uncertain.

Can children tell how different a speaker's accent is from their own? In Experiment 1 (N = 84), four- and five-year-olds heard speakers with different accents and indicated where they thought each speaker lived relative to a reference point on a map that represented their current location. Five-year-olds generally placed speakers with stronger accents (as judged by adults) at more distant locations than speakers with weaker accents. In contrast, four-year-olds did not show differences in where they placed speakers with different accents. In Experiment 2 (N = 56), the same sentences were low-pass filtered so that only prosodic information remained. This time, children judged which of five possible aliens had produced each utterance, given a reference speaker. Children of both ages showed differences in which alien they chose based on accent, and generally rated speakers with foreign accents as more different from their native accent than speakers with regional accents. Together, the findings show that preschoolers perceive accent distance, that children may be sensitive to the distinction between foreign and regional accents, and that preschoolers likely use prosody to differentiate among accents.

Boyer & Petersen suggest that folk-economic beliefs result from evolved domain-specific cognitive systems concerned with social exchange. However, a major challenge for their account is that each folk-economic belief can be explained by different combinations of evolved cognitive systems. We illustrate this by offering alternative explanations for several economic beliefs they discuss.

Mindreading often requires access to beliefs, so the mindreading system should be able to self-attribute beliefs, even without self-interpretation. This proposal is consistent with Carruthers' claim that mindreading and metacognition depend on the same cognitive system and the same information as one another; and it may be more consistent with this claim than is Carruthers' account of metacognition.