Ruth Millikan, University of Connecticut
Karl Popper spoke truly of the unique and transformative human capacity to “let our hypotheses die in our stead.” Though not his intention, Herbert Terrace has recently presented us with evidence suggesting that a more basic capacity on which this capacity rests is also unique to man. Humans may have initiated “declarative” (“indicative”) thought.
The activities at least, say, of mice seem to be guided only by prior experience coupled with current perception of “affordances” (J J Gibson). They neither perceive nor learn that this or that is the case but only how to do things. Humans not only know how to do things, they know that certain things are the case. Besides procedural knowledge, they have declarative knowledge. When, and why, during the evolutionary climb up to man did this capacity to perceive and to know what is the case, to know mere facts, develop?
Herbert Terrace spent three intensive years trying to teach the Chimpanzee Nimchimsky to use sign language. First he claimed success but later after a careful review of his own films and of those made my other researchers he changed his mind. In (Terrace 2019) he presents the conclusions he has reached after 50 years of study. Apes only produce signs that are imperatives. The declarative mood is missing.
- [Chimpanzees fail to learn language] not because they can’t learn grammar, but because they can’t learn the declarative function of words. (Terrace p.129)
- Chimpanzees …will only sign to obtain a reward …. a chimpanzee’s signing differs fundamentally from the spontaneous discourse of infants and children. (Terrace p.49)
This difference between human and ape is to be explained, Terrace offers, by the social and the cooperative nature of the human, who naturally engages in sharing information.
But maybe we can go deeper.
According to ecological psychologists, “perception is for action.” Its original function is to enable recognition and pursuit of affordances, ways that the perceived environment can directly guide one’s movements so as to gain rewards or avoid punishment without the intervention of judgments that this or that is the case. Looking down the stairs you know how to let the perceived shapes and positions of the steps guide your feet and the balance of your body so as to go down without falling. You know how to let your perception of the walls and floor guide you into the kitchen and how to let your perception of the refrigerator guide you in approaching and opening it. If you are hungry and nothing more urgent interferes, the result will soon be food in your belly. A chimpanzee in residence might get himself a snack by using perception in exactly the same way.
We humans use perception in this way every waking moment of our lives, even for keeping ourselves upright in our chairs. Assuming that an animal could learn from experience, this primary use of perception might be sufficient by itself to keep it alive and with luck even flourishing. Perception might be used exclusively for finding out how and then using that knowledge. Animal knowledge might all be just knowing how.
The declarative mood is for stating facts, for sharing factual information.
- Declaratives are truly conversational. Their only function is to transmit information about a mutually interesting object. There is no evidence that … the utterance of any animal is declarative. (Terrace 70)
The obvious difference between the human brain and that of the next lower species, the chimpanzee, is an enormous enlargement of the cortex and the addition to it of a great many folds. Something quite specific appears to have been added, not merely enlarged, in that brain.
A clean and simple, also a temptingly dramatic hypothesis about this addition is that humans began to use an entirely new way of adapting to the environment. Besides allowing behavioral trial and error slowly to teach them how to recognize typical paths toward rewards and away from danger they began to investigate how the environment works by itself. What leads to what, what changes what, what things always happen when and why. Perception began to be used for collecting not just know-how but facts, including dead facts, facts not (yet) known to be of any practical use. The saying is that if stored in the attic for seven years a use for it will be found.
Humans began not just to use the environment but to understand it. We are actively curious about how things work, about what things can be made to do what and why. New techniques for investigating what our world is like continue to be discovered and shared and the resulting knowledge combed for both practical and theoretical uses. Humans began to acquire knowledge of the environment as it exists apart from themselves, knowledge of pure facts. Our own characteristic way of fitting into the environment is by first attempting to understand it, then changing it.
Many animals alter their environments, building homes for themselves, spinning webs, constructing dams. Placed in a new environment they may explore, quickly locating things they might use or need given their own peculiar kind of animal needs. Members of the same species prepare in the same ways, for the utility of these specific kinds of projects and explorations has been discovered during the evolutionary history of the species, not by current members of the tribe.
Perhaps then it was not human language that first introduced the declarative mood but human thought. Many animals have ways of communicating a few determinate kinds of things. Beavers splash, vervets cry snake, many animals have stereotyped ways of communicating when and with whom they are ready to mate. Animals can communicate entirely new things in this way. The time and the place and the individuals to be involved are all freshly designated when at this time and place this male grey goose performs a dance before this female. Very few different kinds of things, however, and no novel things, are communicated in this way. Opportunities for fulfillment of the aims of human thought, however, especially when cooperation must be involved, are immeasurably increased by the use of a human-style language