A large hammer is shown, bearing marks of heavy usage

If I Had a Hammer: Using Tools

Singing can be wonderful to listen to, and human touch has soothing properties. But the singer and the doctor rely on a lot of help from microphones and musicians, as well as stethoscopes and syringes.

We are tool users. What is a cowboy without a gun? A tenderfoot. A shoe salesman without a shoe horn is a greenhorn. Even parents and teachers were admonished that sparing the rod would spoil a child.

A tool amplifies and extends the body, sometimes literally, like a crutch, but sometimes figuratively, through belief, like an amulet.

Tools once defined our roles in society: seamstresses sewed cloth seams and riveters riveted metal seams. Today, business analysts and life coaches don’t bring specific tools to mind, though MacGyver was a hero and we’re fascinated by Swiss Army knives.

Tool use is a behavior. We commonly think of it as using our hands, so let’s begin there. What is it to reach and grasp, behaviors that some writers label prehension?

Hands, of course, appeared before tools. The development of our bipedal gait freed our hands for uses other than locomotion., such as throwing and clubbing and punching. Using our hands to make tools for pounding, cutting and scraping with tools occurred around three million years ago.

The availability of tools changed the way that our hands were useful, too. This is not to say that evolution subserved human superiority, since chimpanzee hands continued to evolve as well; but the divergence between chimps and humans involved a larger change in brain function among the humans.

A small syringe is shown, withdrawing vaccine from a vial.

BIO: Tool use presumably predated human evolution, since it is evident in species that evolved before modern humans did, such as chimpanzees and crows. The question of which species was first to use tools does not strike me as important, since tool use was probably an example of convergent evolution, and any common ancestor of humans, other primates, relatives of crows, octopi and other tool users would have been too early to give a hint of where tool use sprang from. And though we have a single label for tool use, that is no assurance that the behavior is homologous among species.

There is no clear genotype that favors tool use, but there is some evidence that genetic variation can affect tool use in chimpanzees.

More than the hand, the brain is responsible for human tool use, though the brain systems responsible appear to involve frontal, temporal, and parietal lobes of the cerebral cortex and the white matter that connects them, though the supramarginal gyrus of the parietal lobe has come in for special attention in mediating cultural influences on individual action. If these areas provide some insight into the voluntary organization of using tools, the cerebellum must be included for accurate and timely execution, particularly where eye-hand coordination is important.

PSYCHO: The close coordination of visually-guided movements of two hands requires stereopsis, or binocular vision, as well as accurate control of the gaze and the capacity to integrate proprioceptive, visual, and tactile sensation.

For such tasks, the brain has evolved separate pathways for the range and bearing of reaching and the memory-guided identification of objects in the dorsal stream and the ventral stream. The two pathways interact in multiple ways, yet emphasize the “where” and “what” of tools and reaching, respectively.

Since tool use is often not reflexive but planned, it is cognitive in ways that call for explanation. That is, our use of tools is learned and often automatic, but the use is often predicated on context and cannot be predicted to have a fixed latency and species universality as a reflex might.

Eye-hand coordination is one of the lower cognitive skills, but there are others such as an understanding of function that help to distinguish human tool use from what is observed in chimps and crows, which other researchers have termed “intooligence”.

Accounts from archaeology have made it tempting to view the interaction of tool use and the environment as an example of embodied and extended cognition.

While the separation of perception from action in the distinction of dorsal-stream from ventral-stream processing doubtlessly affects tool use, there must be more to the story, particularly within the parietal cortex. Complex plans for tool use may be closely related to the organization of the brain’s representation of the body. Our readiness to perceive opportunities to use tools arises from our perception of affordances, including even the adjustments in grasping that may be necessary for efficient tool use. The dorsal stream is famous for responding to objects in the visual field, but it responds differently according to whether an object is relevant to the task at hand, which is a function that supports the exploitation of affordances. Making the affordance obvious is one challenge facing designers.

The question of how the brain encodes affordances is obviously related to tool use. There are tool-use networks in the human brain. The cortical hand representation may be more important for tool use than the tool area (research here), though earlier imaging studies from the same lab had reported that hand and tool areas in the cerebral cortex were nearly identical. The distinction may be important for understanding how an amputee uses a prosthesis. One influence on the differentiation between tool and hand representations appears to be the expertise of the tool user.

Tool use occurs in a specific area around the body called the peripersonal space. It is organized to permit intimate social contact and the manipulation of tools both safely and effectively. Proximity influences both social responses and the perception of affordances in tool use.

Tools feel like they become a part of the body. Using a tool can make an arm feel longer, and the brain may include tools in its representation of the body. So, though prehistoric tools may be unimpressive to today’s owners of multitools, they started a long process of changing the body, including our brains. Within the span of human tool use, both tools and the human brain have become more sophisticated.

SOCIAL: Some tools are social. They survive from one generation to another in the culture, like the abacus or an amulet. Another example is found among orangutan mothers, who may use infants to grab fruit that lies beyond arm’s reach.

Technology has become a social tool as well. Social media have expanded our social worlds without adequate concern for costs and benefits, and they have made us sensitive to the ethics of their use as tools. They offer challenges that could not be foreseen in an era of physical tools and they remain hard to discern.

In deep space, where tools don’t work as we expect, social connections may also depend on tools appropriate to the environment.

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