I have been reading the excellent book ‘The mind of an ape‘ by David and Ann Premack and also enrolled in a MOOC tiled ‘Origins of the human mind’ offered by Dr. Matsuzawa, so apes have been on top of my mind recently.

Prof Matsuzawa describes an experimental procedure where numerals from 1 to 9 are very briefly displayed on the screen and then masked and the chimpanzee is required to touch the numerals, displayed randomly on the screen briefly, and now invisible as are masked, in ascending order. The chimpanzee is able to perform the task at 80% accuracy, a feat at which if human subjects try they can never succeed (humans perform at 0% accuracy).

We typically pride ourselves as being the epitome of civilization and cognitive abilities, but its humbling to find that there are tasks at which the chimpanzee can excel! This task, in particular, requires immediate memory (sensory/short-term memory) which it seems is better in the chimp.

The different experiments on the chimp also made me think about the underlying structure of memory and reasoning systems. Like humans, it seems chimps too have two different reasoning systems- one tuned to physical world and the other to social/agentic world.

The physical reasoning system is attuned to thinking about causal reasons between psychical objects and events. The question of concern is ‘what caused what?’ . One needs to have a (rudimentary) theory of cause and effect. Some basic understanding of physics is necessary and is instrumental in the development of the capacity of tool use. As a matter of fact too use is one of the ways this physical reasoning system is studied.

The social /agentic reasoning system is attuned to thinking about other con-specifics/ living creatures. It attributes intentions to people and answers ‘who did what to whom?’. One needs to have a (rudimentary) theory of mind to know that others have intentions/ beliefs/ desires etc. A simple paradigm to measure this is whether one understands the visual gaze of a person and can take his/her perspective and know whether the other is able to see something or not.

The physical and social reasoning systems have been show to be different and dissociated in humans and as per one theory are differently accentuated in autistic (more physical reasoning) and schizophrenic (more social reasoning) mind.

Another ability where chimps and humans markedly differ is in their abstract/symbolic representations and linguistic abilities. While chimps can be taught language to a great extent, they don’t develop symbolic language naturally. Language requires abstract and symbolic representation. One can contrast this with the immediate/imaginal representation.

Again, while autistic people have a good immediate/imaginal (thinking/seeing in images instead of words/ symbols) representation system (for e’g’ like in movie ‘rain man’ they can tell the exact number of matchsticks dropped on the floor without counting), their language development is typically hampered , perhaps due to deficits in the abstract/semantic/symbolic representation system.

Thus we see two sets of cognitive functions, and the two sets seem to be slightly at odds with each other: Physical reasoning and concrete/ immediate/imaginal representation; and social reasoning and abstract/semantic/ symbolic representation.

The species  (chimps/humans) who are good at imaginal and physical reasoning system may not be as good at symbolic and the social reasoning system. Similarity within the human family, autistic and schizophrenics may excel at different such functions. While we lost or never gained the ability for highly accurate imaginal system since around 5 MYA when we diverged from chimps and bonobos, we gained the ability for abstract/ symbolic representation. Given the limited real estate that the brain can occupy in any body, its inevitable that as you evolve you lose some and you gain some abilities. Like we lost the ability to use four hands that chimpanzee has.

To summarize, one can associate and link the above to human memory systems. One can conceive of four such memory/reasoning systems:

  1. Visuo-spatial/ short term/ sensory memory: related to immediate memory and imaginal representation.
  2. Procedural memory: related to Physical reasoning/ tool use /physical skills etc and objects representations.
  3. Episodic memory: related to social reasoning and agent representations.
  4. Semantic memory: related to language and symbolism and abstract representations.

Its easy to see how we can apply the same memory/reasoning model to chimps/ other apes without necessarily anthropomorphism. And its equally hard to see and admit that chimps may be better than us at certain cognitive functions and tasks.