The central argument of this target article – that opportunity cost/benefit prioritization (OC/BP) is why human behavior consumes mental effort – is supported by two compelling themes. One is intuitive, has to do with the phenomenology of mental effort, and enables reflective psychological engagement/disengagement. The other is utilitarian and pertains to the idea that “phenomenological experiences are reasonably easy to understand from a [bio]functional perspective” (sect. 5, para. 1; cf. Iran-Nejad et al. Reference Iran-Nejad, Clore and Vondruska1984). Kurzban et al. use these and related ideas skillfully to dislodge the standard resource theory of human endeavor in favor of their promising OC/BP alternative, a feat long overdue. In this commentary, we assume that the computation metaphor, if used for other than a mathematical tool of science, is an Achilles heel; it confines the OC/BP theory to the psychological level; and the theory can survive without it. The purpose of this commentary is to show how OC/BP theory relates to the biofunctional theory of human understanding, including consideration given to the role of biological and computational metaphors in prioritizing opportunities, simultaneity, and mutual exclusion as used in the target article.

The assumption in the target article that cognition is, by nature, computational, adds distance between biology and psychology, in general, and OC/BP and biofunctional theories, specifically (Satyadas et al. Reference Satyadas, Iran-Nejad, Chissom and Chen1993). Without this assumption, the two realms of study have much in common. The trolley dilemmas used in moral research offer an illustration (Greene & Haidt Reference Greene and Haidt2002). In one scenario, participants face the dilemma of either letting a stampeding trolley, about to kill five people on its tracks, roll on, or hitting a re-route switch to send the trolley to a set of side tracks, killing one person instead. In agreement with a computational perspective, most participants are okay with solving the OC/BP dilemma by hitting the switch to save the five and kill only the one (5−1=4). Consider, however, a closely-related variation where no side tracks exist: instead, there happens to be a fat person standing by the tracks. The participant can choose to push and let the trolley run over this person, crushing the unfortunate soul, but, thereby, stopping the trolley and saving the five. Most participants say no to this option. Cognition-as-computation theories leave us in a quandary with the second scenario. Biofunctional science implies that two different kinds of human understanding – biofunctional and psychological (Iran-Nejad & Bordbar Reference Iran-Nejad and Bordbar2013) – interact in a body-mind cycle of adaptation-reflection to explain both scenarios without resorting to the metaphor of cognition as computation (Iran-Nejad Reference Iran-Nejad2012; Iran-Nejad & Gregg Reference Iran-Nejad and Gregg2001), even though there is no argument that computation is an indispensable tool of science.

It is common practice in science to use metaphor; and OC/BP and biofunctional theories rely on computational and biological metaphors, respectively. The computational metaphor builds on the foundation of cognition as computational knowledge (software) – and implies that the minds of organisms contain mathematically exact counters that prioritize, literally speaking, by computing rates of cost/benefit returns. Biofunctional metaphors suggest that OC/BP theory can be understood without risking the reification fallacy inherent in the computational metaphor. Instead, biofunctional science embraces almost literally true biological metaphors, thereby supporting the cycle of mind-body interaction between the complementary types of biofunctional and psychological understanding (Iran-Nejad & Bordbar Reference Iran-Nejad and Bordbar2013). Like in computational theory, in biofunctional science psychological understanding is knowledge-driven, albeit by the fundamentally different kind of non-computational (or intuitive) knowledge. Unlike computational theory, biofunctional science is, first and foremost, based on the foundation of biofunctional understanding. If so, OC/BP theorizing can benefit by disavowing the Achilles heel of computationalism and embracing the more natural ground of biofunctional science. Human understanding is, by evolutionary design, the special biological function of the nervous system, both literally and metaphorically (Iran-Nejad & Gregg Reference Iran-Nejad and Gregg2011; Iran-Nejad & Ortony Reference Iran-Nejad and Ortony1984) – just as breathing is the special function of the respiratory system, and fighting germs is the special function of the immune system.

As is, the OC/BP theory strives to solve the problem of simultaneity at the psychological level. Additionally, claims to the contrary notwithstanding, genuine simultaneity is an anomaly in computationalism, at least as we understand it today (Iran-Nejad Reference Iran-Nejad1989). In biofunctional science, simultaneity is a mutual-inclusion function of ongoing biofunctional activity (OBA) in the nervous and bodily systems (Iran-Nejad & Gregg Reference Iran-Nejad and Gregg2011). The need for prioritization arises when the same systems must engage in momentary constellation firing (MCF) to perform multiple mutually exclusive tasks (Iran-Nejad et al. Reference Iran-Nejad, Marsh and Clements1992). For example, a smile and a frown are mutually exclusive behaviors, to the extent that the same lips, eyebrows, muscles, and the like, must be engaged in performing each of them (Diener & Iran-Nejad Reference Diener and Iran-Nejad1986). Similarly, as the target article illustrates, “foveating one part of the world necessarily precludes foveating other parts of the visual scene” (sect. 2.3, para. 2). Thus, it is in the realm of psychological or behavioral mutual exclusion that the OC/BP and biofunctional theories unite. They part ways in the realm of biology.

In biofunctional science, some of the key ideas of the OC/BP theory apply with renewed vigor. For example, the target article states that prioritization is the general solution to the problem of simultaneity. However, if prioritization means mutual exclusion, what is simultaneity? In biofunctional science, the answer is clear: Prioritization is psychological (i.e., mental or behavioral) mutual exclusion and simultaneity is biofunctional mutual inclusion. This enables a restatement of the foregoing claim in the target article, to saying that prioritization is evolution's psychological, as opposed to general, solution to the problem of biofunctional simultaneity (Iran-Nejad & Bordbar Reference Iran-Nejad and Bordbar2013). Specifically, simultaneity in biofunctional science is auto-regulated (or effortless) mutual inclusion in ongoing biofunctional activity in the nervous and bodily systems, and priority is (effortful) mutual exclusion caused by momentary constellation firing in the neurons of the nervous system. Moreover, OBA and MCF work together complementarily in the body-mind cycle of adaptation/reflection (Iran-Nejad Reference Iran-Nejad2000; Iran-Nejad & Gregg Reference Iran-Nejad and Gregg2001; Reference Iran-Nejad and Gregg2011; Prawat Reference Prawat2000). The mutual inclusion/exclusion theory started as an explanation for the quantitative and qualitative shifts in simultaneity and separation between affective valences when understanding surprise-ending stories, and soon became one of the leading theories in affective science (Brehm & Miron Reference Brehm and Miron2007; Diener & Iran-Nejad Reference Diener and Iran-Nejad1986; Iran-Nejad Reference Iran-Nejad1980; Reference Iran-Nejad1989; Iran-Nejad et al. Reference Iran-Nejad, Clore and Vondruska1984; Iran-Nejad & Ortony Reference Iran-Nejad and Ortony1984; Reference Iran-Nejad and Ortony1985; Schimmack Reference Schimmack2001).