There are many definitions for intelligence as well as types of intelligence. Most definitions include lists of activities inherent to humans, such as reasoning, planning, solving problems, thinking abstractly, comprehending complex ideas, learning from experience, and adapting effectively to the environment. When attempting to develop intelligent machines, researchers try to make them perform a subset of those activities with as high a level of plausibility as possible. However, from the standpoint of knowledge formalization and for a more precise formulation of research goals, it would be useful to point out the smallest subset of activities, which when performed by an animate being or inanimate machine, can be considered as an indication that it is intelligent enough.
First, it is necessary to mention that intelligence implies a goal (in the “Handbook of Human Intelligence” Sternberg and Salter defined intelligence as “goal-directed adaptive behavior”). In the case of animate being, the goal is surviving, in the case of a machine created by humans the goal is solving tasks assigned by humans. Animals show their basic intelligence, e.g. when they adapt to the environment, seek for food, and build nests. One can say today's machines show their intelligence by effectively doing tasks they are intended to do. This is not a too distorted interpretation of intelligence if we review the book “Symbolic Logic and Intelligent Machines” of Edmund C. Berkeley published in 1959, where the author called intelligent machines the electromechanical arrangements, which solve problems that involve logic.
The advanced level of intelligence can be defined as the production and use of work tools. As it has turned out, the production and use of work tools is peculiar not only to humans, but also to chimpanzees and to a number of other animals. For example, chimpanzees are able to find stones of appropriate weights and sizes and crack nuts using them. Another kind of activity using tools that chimpanzees are able to do is find long and thin sticks to kill small rodents, which live in the trunks of a certain species of trees, and extract them for food. The chimpanzees not only find ready-to-use work tools in nature, but they can also produce them. For example, chimpanzees can construct arrangements consisting of small tree branches and put them into termite mounds to eat termites that crawled on them. Another notable example is an experiment conducted on a pygmy chimpanzee when he was successfully trained to manufacture a sharp stone tool to cut the string, which opens the door of the trap and gives him access to sweets.
In the digital world supported by computers, work tools are computer programs that help to solve various tasks. That is, in the computer environment, the advanced level of intelligence is closely connected with a capability of synthesis and use of algorithms. A machine with an advanced level of intelligence must be capable of automated synthesis of algorithms in some form or fashion. Such machines could then internally generate a computer program, possibly consisting of a set of subroutines, which solves a task assigned by a human.
There does exist a higher level of intelligence, which is peculiar only to humans and not to chimpanzees that we will call an expert level of intelligence. Indeed, in what manner do humans and chimpanzees differ in essence if they both can produce and use work tools? One can say humans perform their activity consciously and chimpanzees do not posses that degree of consciousness. Such explanations are worthless from both scientific and practical viewpoints because when a chimpanzee does something, he can consider that he does it with the full consciousness and awareness of what he does and why.
In the book “The complete idiot's guide to Human Prehistory,” its author Robert J. Meier carefully pointed out an important fact about the production and use of burins. Such specially sharpened stones archaeologists find during excavations that correspond to the time, starting from which, tentatively speaking, creatures that have been living on Earth could be called humans. Burins are tools created for manufacturing other tools. Chimpanzees do not make tools for making other tools. That is, the expert level of intelligence peculiar only to humans consists of the ability to organize processing chains in which one kind of work tool is used to produce other kinds of work tools. The established concept for this is “production of the means of production.”
In the computer environment, programmers create such tools as compilers, various operating, execution, and development environments that help to create other computer programs. A machine with an expert level of intelligence created by humans would be one that is capable of the automated synthesis of algorithms, which the machine will use to synthesize other algorithms to solve problems assigned by humans more efficiently. Creation of such a machine is a quite specific goal that researchers could try to achieve.