According to Jerry Fodor, the author of Modularity of Mind, a system can be considered 'modular' if its functions are made of multiple dimensions or units to some degree.
The second can be characterized as a vertical view because it claims that the mental faculties are differentiated on the basis of domain specificity, are genetically determined, are associated with distinct neurological structures, and are computationally autonomous.
Gall claimed that the individual mental faculties could be associated precisely, in a one-to-one correspondence, with specific physical areas of the brain.
According to Frankenhuis and Ploeger, domain-specificity means that "a given cognitive mechanism accepts, or is specialized to operate on, only a specific class of information".
[8] Leda Cosmides and John Tooby claimed that modules are units of mental processing that evolved in response to selection pressures.
To them, each module was a complex computer that innately processed distinct parts of the world, like facial recognition, recognizing human emotions, and problem-solving.
The rapidity of responses such as jealousy due to infidelity indicates a domain-specific dedicated module rather than a general, deliberate, rational calculation of consequences.
Clune et al. (2013) have argued that computer simulations of the evolution of neural nets suggest that modularity evolves because, compared to non-modular networks, connection costs are lower.
[13] Several groups of critics, including psychologists working within evolutionary frameworks,[14] argue that the massively modular theory of mind does little to explain adaptive psychological traits.
[16][17] Moreover, critics argue that Cosmides and Tooby's conclusions contain several inferential errors and that the authors use untested evolutionary assumptions to eliminate rival reasoning theories.
[16][18] Criticisms of the notion of modular minds from genetics include that it would take too much genetic information to form innate modularity of mind, the limits to the possible amount of functional genetic information being imposed by the number of mutations per generation that led to the prediction that only a small part of the human genome can be functional in an information-carrying way if an impossibly high rate of lethal mutations is to be avoided, and that selection against lethal mutations would have stopped and reversed any increase in the amount of functional DNA long before it reached the amount that would be required for modularity of mind.
"[14] Philosopher David Buller agrees with the general argument that the human mind has evolved over time but disagrees with the specific claims evolutionary psychologists make.
[21] He has suggested that the "modules" result from the brain's developmental plasticity and that they are adaptive responses to local conditions, not past evolutionary environments.
A staunch defender of this view is William Uttal, who argues in The New Phrenology (2003) that there are serious philosophical, theoretical, and methodological problems with the entire enterprise of trying to localise cognitive processes in the brain.
Merlin Donald argues that over evolutionary time the mind has gained adaptive advantage from being a general problem solver.