The Evolution of Agency – Part 2

Mammalian executive function.

Continuing this series of essays, we’ll explore the evolutionary origins of human agency, the key steps in that development, and the need for society to uphold the types of social arrangements that made the development of human agency possible in the first place.  Michael Tomasello, in his book The Evolution of Agency: Behavioral Organization from Lizards to Humans, writes:

[T]he selection pressures leading to behavioral agency arise when a population of organisms moves into an ecological niche rife with unpredictabilities, for example, clever prey and predator species. The point is that when the environment always repeats itself (e.g., in filter feeders, food is always just an open mouth and a few wiggles away), then hardwired, open-loop, stimulus-driven behavioral organization works just fine. But when novelty and unpredictability arise, stimulus-response organization leads to failure, as the individual is always “fighting the last war.” With feedback control organization, Nature can still hardwire the most important goals but at the same time empower the individual to pursue them flexibly by attending to relevant situations and making informed behavioral decisions. The lizard does not choose to crave tasty crickets; it chooses how to pursue this cricket now … If a new insect species suddenly appears, lizards cannot be behaviorally adapted for capturing it precisely because it is new; it has never before been a part of their ecological niche. Nevertheless some individuals may be able to use their flexible, agentive powers of goal-directed attention and decision-making to extend their existing behavioral skills to make the new insect a part of their diet. Because this new extension of behavior comes into existence not because of any genetic changes but because of the exercise of behavioral agency, we may say that to some significant degree, the agent and its flexibly organized skills play a causal role in the process of evolutionary change. The organism’s newly effective actions now make possible genetic changes that serve to support the organism’s pursuit of the new insect (so-called genetic assimilation) … Lizards and other reptiles are thus behaviorally flexible decision-makers—compared to C. elegans [an early worm]. But compared to mammals, their behavior is still a bit stereotyped and inflexible. The explanation is that along with the emergence of mammals some 200 million years ago came a huge new jump in behavioral agency based on a fundamental reorganization of how individuals direct and control their actions. Mammals direct their actions toward goals not just flexibly but intentionally, as they cognitively simulate possible action plans toward their goal before actually acting. And they control their behavior not just by making go-no-go decisions but also by making either-or behavioral choices as they evaluate the possible plans’ likely outcomes and then cognitively monitor and control behavioral execution as it unfolds.

Sociality was the key first step in the development of mammalian agency:

The first mammals in the lineage on the way to humans were small, squirrel-like creatures about 200 million years ago … The key for early mammals was their new social niche. Whereas reptiles are mostly solitary foragers, most mammals live and forage in a social group of one type or another … Thus, in addition to complexities created by their foraging ecologies, early mammals had to deal with complexities created by enhanced competition with group mates for food and other resources. When the whole group finds a patch of food at the same time, there is a premium on making fast, efficient foraging decisions. Since those group mates are in exactly the same situation, a kind of “arms race” of cognitive skills for outcompeting conspecifics for access to food can occur … In addition, many mammals compete with others by cooperating with coalition partners in teams based on social relationships. Operating in this newly complex socioecology led early mammals to evolve a new manner of functioning involving not only new psychological skills and motivations but also new ways for making decisions more efficiently … Early mammals’ new manner of functioning comprised three new psychological capacities, organized in a new way. First, mammals evolved new ways to motivate their action: not just by an ineluctable attraction to a goal, but rather by more flexible motivations and emotions. Instead of a more or less fixed reaction to a predator, for example, mammals evolved an internal psychological state, the emotion of fear, that precipitated an “action tendency” to flee, but with the flexibility to do something else if that would be more beneficial … [S]ocial competition with group mates puts a premium on avoiding costly mistakes in decision-making, effected, for example, by planning before acting via imaginative cognitive simulations and then monitoring and supervising execution of the planned action. In terms of brain bases for these new cognitive skills, mammals have a six-layered neocortex that greatly exceeds the three-layered structure of reptiles in number of neurons and neural subtypes, as well as many more functionally differentiated areas and a corpus callosum between hemispheres that facilitates more rapid information processing.

Mammals have the advantage of having more time to learn before “leaving the nest”:

[M]ammals [also] evolved a new ontogenetic (life history) pattern involving much more learning. Individual mammals develop slowly and in interaction with the environment (rather than quickly and inside an egg, as in reptiles). In the early stages of life, mammalian infants can count on their mother’s milk for nutrition and on her vigilance for their protection and safety. This life history pattern is costly for mothers and risky for infants. A major compensating advantage is that the infant, who does not have to spend time and energy seeking food and escaping predators, can focus on learning about its local environment (and learning in play, which is arguably absent in reptiles). By the time they reach adulthood, individual mammals have learned many things, which can be unlearned or modified more easily than more hardwired behavioral adaptations.

This helped mammals achieve an ability to engage in executive action:

The way that mammals direct their actions via more flexibly motivated goals and more powerful skills of cognition and learning leads to a more flexible version of our basic feedback control system. The key to this new version is the functioning of a wholly new tier of psychological organization: the executive tier. This new executive tier enables more flexible forms of planning and decision-making that output not an action but an intention to act, with the further possibility of self-regulating the fidelity of the intention’s translation into action. Mammals thus became intentional agents … [Agency] requires individuals to cognitively simulate in an organized way their own potential actions, the potential obstacles and opportunities for those actions, and the probable outcomes of those actions. They do this by perceptually imagining all these action elements in the common cognitive workspace and representational format provided by an executive tier of operation. This new form of mental activity is supported by mammals’ greatly expanded prefrontal cortex—the widely recognized home of most executive functions—as compared with reptiles and other goal-directed agents … Mammals’ actions are thus not just goal-directed but intentional; cognitive simulation and planning enable the individual to organize and choose its actions more flexibly and on their relative merits … The executive goal is to make a “better” behavioral decision than would otherwise be made by the operational tier. The individual attempts to make a better decision—in the context of its cognition, knowledge, and values—by imaginatively simulating multiple action plans and their anticipated outcomes proactively, and then evaluating those plans and their outcomes to make an either-or decision. This results not in an action but in an intention to act, which guides the organism’s action by serving as a kind of template at which action execution aims.

Watch your local squirrels for glimpses at mammalian executive function:

In contrast to lizards and other reptiles, squirrels and other mammals often make either-or decisions prospectively among cognitively represented behavioral options before they act. Consider the following observation. A squirrel is perched on a tree branch and is trying to decide whether to get to a new location by either leaping to another branch some meters away or climbing down the trunk and out that branch. The squirrel coils in preparation to jump but then backs down. It coils again and backs down again. Finally it gives up and ambles down the branch onto the tree trunk and then out the desired branch. What has happened here? One possibility is that the squirrel has run a kind of cognitive simulation. It has imagined (in a kind of off-line perception) what would happen in the situation if it leaped for the branch, and what would happen if it walked down and around, comparing the two options in a process of mental trial and error in which failure is not fatal but informative … Decision-making of this kind involves two sets of component processes in a constant dialogue: simulating or imagining alternatives cognitively, and evaluating each so as to choose among them … The process of cognitively simulating possible actions and their outcomes is called planning …. [I]n the studies of squirrels and other mammals just reviewed, individuals were not just inhibiting (freezing) one action reactively and then looking around for what else they could do (as the lizards did). Rather, the mammals were prospectively considering simultaneously two behavioral options and inhibiting one of them in acts of either-or decision-making, as evidenced especially by their pausing and visually alternating between choices before acting, and in the opt-out studies by their active assessment of their possible options before acting. What we call inhibition in mammals is therefore perhaps just an integral part of value-based choice among multiple alternative action possibilities, in which the prevision that some potential actions will fail leads to their devaluation relative to others. This is not just simple or global inhibition but a more proactive process of what we might call inhibitory control … Thus skills of inhibitory control would be useful for an individual to delay going for a small amount of resources here and now in favor of traveling farther for a larger amount later (delay of gratification), which many mammals have been observed to do.

In a previous essay series, we saw the vast benefits imparted to people who can exercise self-control.  And here we see how important exercising self-control was to the evolution of humans in the first place.

In the next essay in this series, we’ll examine how sociality allowed mammals to exponentially increase their capacity for agency.