Is the Mind a Swiss-Army Knife or a Crowbar?

Image: A vintage and somewhat unscientific map of mental functions. But how fine grained are these adaptations?

– by Thomas J. H. Morgan

From the outside, the brain is a medium sized, pinkish-grey blob. At the microscopic level, it’s a densely woven mesh of countless neurons. In between these two extremes is the brain’s functional structure – the mind, or more concretely, how those neurons are wired together to solve problems and manage behavior.

A popular metaphor for the mind is the Swiss-army knife. Like the brain, the Swiss-army knife has a large-scale external appearance (red, cigar-shaped, with silver rotating appendages) and a microscopic constitution (atoms and molecules). However, it also has a functional mid-level structure, being composed of subunits that solve particular problems – opening bottles, filing nails, driving screws, scaling fish, cutting wires, and so on.

As useful as it is, the Swiss-army knife has limitations. Screwdrivers and fish scalers aren’t much use without screws or a means to catch fish. Someone heading out into the unknown might instead prefer a kit of fewer but more widely applicable tools. Say, an axe and a crowbar. Rather being designed for specific problems, these items can be put to work in many contexts and so can handle unforeseen situations more successfully.So, what does the mind look like – a bespoke Swiss-army knife with many task-specific solutions, or an adaptable survival kit of just a few broadly applicable tools? This is the question we set out to answer. We recruited groups of participants and had them collectively complete a task. The task we chose was mate-choice copying – participants evaluated how attractive they found photos of other people, and then they saw what other participants thought and could alter their decision.

Mate-choice copying is particularly relevant to this question as it sits at the interface of two fields – evolutionary psychology, which has collected lots of data on human mate choice, and cultural evolution, which has extensively studied copying and social influence. In addition, while some prior work on mate choice copying has suggested it is managed by a mental adaptation evolved specifically for this task, other work has argued the mental system is broader and handles decision making and learning more generally.

Prior work led by Dr. Sally Street had already found that humans were equally influenced by what others thought about the attractiveness of human faces, human hands and abstract art, but we wanted to dig into the details. Studies of copying across many other contexts have documented that humans are influenced by majorities (“conformity”) as well as by successful individuals (“prestige”). We tested whether these same patterns occurred in mate-choice copying. In addition, we collected data from both men and women to see if there were gender differences in copying. Our reasoning was that the more mate-choice copying differed between genders or from copying in other contexts then the more likely it was underpinned by a mate-choice specific adaptation.

Our results showed the opposite. Participants were influenced by each other’s decisions, and analysis of the patterns in this copying found strong evidence of both conformity and prestige. In addition, there was strong evidence that both men and women copied in the same way. We thus concluded that rather than a bespoke system, mate choice-copying is underpinned by the same copying mechanisms that are active in other contexts – it’s a crowbar, not a Swiss-army knife.

There are two important points though. First, although we suggest the mind is made of general-purpose systems, these systems are still adaptations – they are just adaptations for broad classes of problems, as opposed to specific tasks. Second, even broadly applicable systems can be flexibly tuned to meet particular needs. For instance, copying is known to be adjusted according to factors like confidence and risk. Through factors like these, even broad ranging systems can be adaptively tuned for particular tasks, just like a crowbar can be applied with different amounts of force. Thus, the mind might have fewer solutions than the Swiss-army knife metaphor suggests, but its adaptive power comes from the flexible use of the tools at its disposal.

Read the original article: Foreman, M., & Morgan, T.J.H. (2024). Prestige, conformity and gender consistency support a broad-context mechanism underpinning mate-choice copying. Evolution and Human Behavior, 45(1), 58-65.