Scientists suggest the brain may work best with 7 senses, not just 5

"Our conclusion is of course highly speculative in application to human senses, although you never know: It could be that humans of the future would evolve a sense of radiation or magnetic field. But in any case, our findings may be of practical importance for robotics and the theory of artificial intelligence," said study co-author Professor Nikolay Brilliantov of Skoltech AI. "It appears that when each concept retained in memory is characterized in terms of seven features—as opposed to, say, five or eight—the number of distinct objects held in memory is maximized."

Following a research tradition that began in the early 20th century, the team focused on modeling the basic units of memory known as “engrams.” An engram can be thought of as a sparse collection of neurons in different brain regions that fire together. Each engram represents a concept, described through a set of features. For humans, these features correspond to sensory experiences—for example, the concept of a banana includes its appearance, smell, taste, and other sensory qualities. In this framework, the banana becomes a five-dimensional object within a mental space containing all the other memories stored in the brain.

Engrams evolve over time, becoming sharper or more diffuse depending on how often they are triggered by sensory input from the outside world. This process represents how we learn and forget as we interact with our environment.

"We have mathematically demonstrated that the engrams in the conceptual space tend to evolve toward a steady state, which means that after some transient period, a 'mature' distribution of engrams emerges, which then persists in time," Brilliantov commented. "As we consider the ultimate capacity of a conceptual space of a given number of dimensions, we somewhat surprisingly find that the number of distinct engrams stored in memory in the steady state is the greatest for a concept space of seven dimensions. Hence the seven senses claim."

In other words, let the objects that exist out there in the world be described by a finite number of features corresponding to the dimensions of some conceptual space. Suppose that we want to maximize the capacity of the conceptual space expressed as the number of distinct concepts associated with these objects. The greater the capacity of the conceptual space, the deeper the overall understanding of the world. It turns out that the maximum is attained when the dimension of the conceptual space is seven. From this the researchers conclude that seven is the optimal number of senses.

According to the researchers, this number does not depend on the details of the model -- the properties of the conceptual space and the stimuli providing the sense impressions. The number seven appears to be a robust and persistent feature of memory engrams as such. One caveat is that multiple engrams of differing sizes existing around a common center are deemed to represent similar concepts and are therefore treated as one when calculating memory capacity.

The memory of humans and other living beings is an enigmatic phenomenon tied to the property of consciousness, among other things. Advancing the theoretical models of memory will be instrumental to gaining new insights into the human mind and recreating humanlike memory in AI agents.