When do humans become moral beings? This commentary draws on developmental psychology theory to expand the understanding of early moral behaviours. We argue that by looking at a broader range of other-oriented acts than what has been considered by Baumard et al., we can find support for the mutualistic approach to morality even in early instances of other-oriented behaviours.

Market models are indeed indispensable to understanding the evolution of cooperation and its emotional substrates. Unfortunately, Baumard et al. eschew market thinking in stressing the supposed invariance of moral/cooperative behavior across circumstances. To the contrary, humans display contingent morality/cooperation, and these shifts are best accounted for by market models of partner choice for mutually beneficial collaboration.

I make three points. First, processors and depletable resources should not be regarded as alternative means of processing information: they are both necessary. Second, comparing a processor account with a rational allocation mechanism to a depletable-resources account without one is not a fair comparison. Third, depletable resources can act as signals as well as fuels.

Jeffery et al. accurately identify the importance of developing an understanding of spatial reference frames in a three-dimensional world. We examine human spatial cognition via a unique paradigm that investigates the role of saliency and adjusting reference frames. This includes work with adults, typically developing children, and children who develop non-typically (e.g., those with autism).

Quantum probability theory offers a viable alternative to classical probability, although there are some ambiguities inherent in transferring the quantum formalism to a less determined realm. A number of physicists are now looking at the applicability of quantum ideas to the assessment of physics learning, an area particularly suited to quantum probability ideas.

The notion of an enactive system requires thinking about the brain in a way that is different from the standard computational-representational models. In evolutionary terms, the brain does what it does and is the way that it is, across some scale of variations, because it is part of a living body with hands that can reach and grasp in certain limited ways, eyes structured to focus, an autonomic system, an upright posture, etc. coping with specific kinds of environments, and with other people. Changes to any of the bodily, environmental, or intersubjective conditions elicit responses from the system as a whole. On this view, rather than representing or computing information, the brain is better conceived as participating in the action.

Different to Kurzban et al., we conceptualize the experience of mental effort as the subjective costs of goal pursuit (i.e., the amount of invested resources relative to the amount of available resources). Rather than being an output of computations that compare costs and benefits of the target and competing goals, effort enters these computations as an input.

Through the mental alignment that sustains social interactions, the minds of individuals are shared. One interpretation of shared intentionality involves the ability of individuals to perceive features of the action scene from the perspective of the group (the “we-mode”). This first-person plural approach in social cognition is distinct from and preferable to the second-person approach proposed in the target article.

I propose that it is premature to assert that a fully three-dimensional map has never evolved in any species, as data are lacking to show that space coding in all animals is the same. Instead, I hypothesize that three-dimensional representation is tied to an animal's mode of locomotion through space. Testing this hypothesis requires a large body of comparative data.

We are sympathetic to the general ideas presented in the article by Pothos & Busemeyer (P&B): Heisenberg's uncertainty principle seems naturally relevant in the social and behavioral sciences, in which measurements can affect the people being studied. We propose that the best approach for developing quantum probability models in the social and behavioral sciences is not by directly using the complex probability-amplitude formulation proposed in the article, but rather, more generally, to consider marginal probabilities that need not be averages over conditionals.

Studies of economic decision-making have revealed the existence of consistent contributors, who always make contributions to the collective good. It is difficult to understand such behavior in terms of mutualistic motives. Furthermore, consistent contributors can elicit apparently altruistic behavior from others. Therefore, although mutualistic motives are likely an important contributor to moral action, there is more to morality than mutualism.

The rich diversity of avian natural history provides exciting possibilities for comparative research aimed at understanding three-dimensional navigation. We propose some hypotheses relating differences in natural history to potential behavioral and neurological adaptations possessed by contrasting bird species. This comparative approach may offer unique insights into some of the important questions raised by Jeffery et al.

Quantum probability (QP) theory provides an alternative account of empirical phenomena in decision making that classical probability (CP) theory cannot explain. Cognitive architectures combine probabilistic mechanisms with symbolic knowledge-based representations (e.g., heuristics) to address effects that motivate QP. They provide simple and natural explanations of these phenomena based on general cognitive processes such as memory retrieval, similarity-based partial matching, and associative learning.

Baumard et al. mischaracterize our model of individual and social choice behavior. We model individuals who maximize preferences given their beliefs, and subject to their informational and material constraints (Fehr & Gintis 2007). Individuals thus must make trade-offs among self-regarding, other-regarding, and character virtue goals. Two genetic predispositions are particularly crucial. The first is strong reciprocity. The second is the capacity to internalize norms through the socialization process. Our model includes the authors' model as a subset.

A second-person perspective in neuroscience is particularly appropriate for the study of communication. We describe how the investigation of joint language tasks can contribute to our understanding of the mechanisms underlying interaction.

One shortcoming of Kurzban et al.'s model is that it is not clear how animals persist through subjectively effortful tasks, particularly over a long time course. We suggest that the anterior cingulate cortex plays a critical role by encoding the utility of an action, and signalling where efforts should be best directed based on previous and prospected experience.

Mutualism provides a compelling account of the fairness intuitions on display in economic games. However, it is not yet clear how well the approach holds up as an explanation of all human morality. The theory needs to be tested outside the methodological neighborhood it was born in; such testing has the potential to greatly improve our understanding of morality in general.

Single-cell studies of monkey posterior parietal cortex (PPC) have revealed the extensive neuronal representations of three-dimensional subject motion and three-dimensional layout of the environment. I propose that navigational planning integrates this PPC information, including gravity signals, with horizontal-plane based information provided by the hippocampal formation, modified in primates by expansion of the ventral stream.

Evolution would favor organisms that can make recurrent decisions in accordance with classical probability (CP) theory, because such choices would be optimal in the long run. This is illustrated by the base-rate fallacy and probability matching, where nonhumans choose optimally but humans do not. Quantum probability (QP) theory may be able to account for these species differences in terms of orthogonal versus nonorthogonal representations.

In the target article, Schilbach et al. defend a “second-person neuroscience” perspective that focuses on the neural basis of social cognition during live, ongoing interactions between individuals. We argue that a second-person neuroscience would benefit from formal approaches borrowed from economics and behavioral ecology and that it should be extended to social interactions in nonhuman animals.