The answer to this question carries bad news and good news. The bad news is that human cognitive abilities, including memory and intelligence are limited by many variables including time. The good news is that, within those limits there is room for a prodigious memory and remarkable intellectual achievements. What limits human cognitive abilities?
Perhaps the greatest limits on our cognitive abilities derive from human lifespan. We have a brief window of time in which to build the neural structure of our brain and then we reach a period when our fluid intelligence (neural efficiency for processing ideas) begins to decline, although we continue to build knowledge and increase our neural information base. These two components of our intelligence are shown in a time-line in the graph below.
We see in the graph that our intelligence increases during the first 5 decades of life; however our fluid intelligence goes into decline shortly after we reach adulthood. As we continue to learn and develop knowledge and experience through the following decades, our intelligence increases reaching a peak sometime in our 6th decade of life. It is in the span between our mid 20’s and mid 50’s that we make most of our intellectual contributions and then the gradual decline sets in. (See: At What age Does one pass his/her intellectual peak? – Intelligence and IQ )
However, the good news is that some human brains can acquire a great deal of learning in a very short period of time. By age 13, mathematician Sir William Rowan Hamilton had acquired, through his uncle’s tutelage, some degree of fluency in about a dozen Indo-European languages. Physicist, John von Neumann was readily recognized as a child prodigy, possessing an eidetic memory and at age 6 displayed the ability to divide two eight-digit numbers in his head. His family often entertained guests with demonstrations of his prodigious memory. By age 8, he had become proficient in calculus. Terrence Tao, learned to read at two years of age. By the time these child prodigies reached their intellectual peak, they had contributed significantly to human knowledge and technology.
With the advances in computer technology, we humans are creating artificial intelligence in computers made with inanimate materials that don’t suffer the biological decline that we experience. This enables us to preserve knowledge (unlimited memory) and achieve enhanced fluid intelligence in the form of rapid processing skills. Computers that can execute billions of operations in a fraction of a second have expanded the reach of human cognition. (See Is AI more intelligent than the people who created it? – Intelligence and IQ )
One significant impediment to human intelligence may reside in the fact that we have only 5 senses and there may well be phenomena outside our perception, so that we are entirely unaware of their existence. For example, if we didn’t have the faculty of eyesight, we might have difficulty understanding the concept of camouflage in the animal world. Heisenberg’s Uncertainty Principle tells us that there are limits to what we can know about things we can’t perceive directly. And Gödel’s completeness theorems indicate that there are some mathematical statements that are undecidable, i.e., that we will never be able to prove or disprove. What we perceive as “reality” may well be a human construct formed from our perceptions. Even the most intelligent people on our planet have limited cognitive powers, but the limits are sufficiently expansive to enable us to enjoy a quality of life that those of past generations could only imagine.
