DA said:
Careful, conceptualizing as “forming mental pictures” is a very misleading idea. It might be best to ask, “can other animals perform abstraction?”. When we abstract we let go of visual memory for a symbol. I ask the question: " Can any of the monkeys that are taught to sign, make the connection-symbolize, "that boat looks like a banana. I’ll call it a “banana boat” "?..
From Merriam-Webster:
Concept: an idea of what something is or how it works
Conceptualize: to form (an idea, picture, etc.) of something in your mind
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From Great ape language, Wikipedia: http://en.wikipedia.org/wiki/Great_ape_language
Differentiation: Washoe used the sign “more” in many different situations until a more specific sign had been learned. At one point, she used the sign for “flower” to express the idea of “smell.” After additional training, Washoe was eventually able to differentiate between “smell” and “flower.”
Transfer: Although the same object was presented for each learning trial (a specific hat, for example), Washoe was able to use the sign for other similar objects (e.g. other hats).
Combinations: Washoe was able to combine two or three signs in an original way. For example, “open food drink” meant “open the fridge” and “please open hurry” meant “please open it quickly.”
Washoe also taught other Chimpanzees some ASL without any help from humans.
Sarah and two other chimpanzees, Elizabeth and Peony, in the research programs of David Premack, demonstrated the ability to produce grammatical streams of token selections. The selections came from a vocabulary of several dozen plastic tokens; it took each of the chimpanzees hundreds of trials to reliably associate a token with a referent, such as an apple or banana. The tokens were chosen to be completely different in appearance from the referents. After learning these protocols, Sarah was then able to associate other tokens with consistent behaviors, such as negation, name-of, and if-then. The plastic tokens were placed on a magnetic slate, within a rectangular frame in a line. The tokens had to be selected and placed in a consistent order (a grammar) in order for the trainers to reward the chimpanzees.
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All of the above, beyond demonstrating an ability to learn an alien language (no small trick), tends to evaluate chimpanzee intelligence qua man, albeit a very hungry man. Were Sara or Washoe to see a boat that looks like a bananna they’d more likely call it a “wet yummy”.