Cognitive neuropsychology considerably started in the second half of the 19th century after the discoveries of aphasia, disorders affect comprehension and production of spoken language. The famous French surgeon Paul Broca applied the principle of experimental ablation, which was previously done in animal by Pierre Flourens, a French physiologist, to the human brain.
The modern science of cognitive neuropsychology emerged during the 1960s as a reaction to behaviorism. Scientists realized that there were other sources of data and consciousness became a major area of interest. A particular area of interest for cognitive psychologists was memory. By studying patients with amnesia, which was caused by injuries to the medial temporal cortex, scientists were able to determine the affected areas of the brain. A patient with amnesia will not be able to remember events of the previous day (episodic memory, ) but they will still remember how to tie their shoes (procedural memory, ) remember a series of numbers for a few seconds (working memory) and be able to recall historical events they have learned in school (semantic memory.) Many other studies like this have been done in the field of neuropsychology examining lesions and the effect they have on certain areas of the brain and their functions.
The case of Phineas Gage was one of the earliest in which a brain injury provided clues to the function of a particular brain area. Gage survived an 1848 accident in which an iron rod 1¼ inches in diameter was driven through his head, destroying most or all of his left frontal lobe. Though he suffered no loss of sensory or motor function, Gage's consequent personality changes prevented his return to his position as a railway construction foreman (though most presentations of Gage greatly exaggerate his psychological changes—.Broca's area and Wernicke's area.
Similarly, Paul Broca's 1861 post mortem study of an aphasic patient, known as "Tan" after the only word which he could speak, showed that an area of the left frontal lobe was damaged. As Tan was unable to produce speech but could still understand it, Broca argued that this area might be specialised for speech production and that language skills might be localized to this cortical area. Broca did a similar study on another patient, Lelong, a few weeks later. Lelong, like Tan, could understand speech but could only repeat the same 5 words. After examining his brain, Broca noticed that Lelong had a lesion in approximately the same area as his patient Tan.  He also noticed that in the more than 25 patients he examined with aphasia, they all had lesions to the left frontal lobe but there was no damage to the right hemisphere of the brain. From this he concluded that the function of speech was probably localized in the inferior frontal gyrus of the left hemisphere of the brain, an area now known as Broca's area.
The discoveries of Paul Broca and Carl Wernicke are considered fundamental for later cognitive-neuropsychological approaches such as Lissauer’s object recognition in 1890 and Lewandowsky and Stadelmann’s calculation in 1908. However, cognitive neuropsychology received less public attention in the early 20th century because of the major changes in two fields: psychology (John B. Watson and his famous behaviorism doctrine that was proposed in 1913) and neurology (Pierre Marie’s conclusions against previous evidence of Broca’s areas in 1906 and Henry Head’s attack on the whole field of neuropsychology in 1926). These major changes in psychology and neurology did not only affect and improve public understanding of treatment of psychological disorders but also broaden our perspectives on cognitive psychology and cognitive neuropsychology. As a result, changes in these perspective led to the “Cognitive Revolution” in mid 20th century. The “Cognitive Revolution” was the time period when John B. Watson’s behaviorism was no longer favored and psychology was not considered the science of behavior. Psychologists in the mid-1950s acknowledged that the structure and nature mental information-processing systems could be investigated in scientifically acceptable ways. They developed and applied new cognitive processing models to explain experimental data from not only studies of speech and language but also those of selective attention.
Clues about the role of the occipital lobes in the visual system were provided by soldiers returning from World War I. The small bore ammunition often used in this conflict occasionally caused focal brain injuries. Studies of soldiers with such wounds to the back of their head showed that areas of blindness in the visual field were dependent on which part of the occipital lobe had been damaged, suggesting that specific areas of the brain were responsible for sensation in specific visual areas, known as retinotopy.Most of Molaison's hippocampus was removed bilaterally.
Studies on Henry Molaison, formerly known as patient H.M., are commonly cited as some of the precursors, if not the beginning of modern cognitive neuropsychology. Molaison had parts of his medial temporal lobes surgically removed to treat intractable epilepsy in 1953. Much of the hippocampus was also removed along with the medial temporal lobes. The treatment proved successful in reducing his dangerous seizures, but left him with a profound but selective amnesia.After the surgery, Molaison's long term memory was still intact, but he no longer had short term memory. He was still able to remember big events from before the surgery, such as the stock market crash in 1929, but he could no longer form new memories. This accidental experiment showed scientists how the brain processes different types of memory. Because Molaison's impairment was caused by surgery, the damaged parts of his brain were precisely known, information which was usually not knowable in a time before accurate neuroimaging became widespread. Scientists concluded that while the hippocampus is needed in the creation of new memories, it is not needed in the retrieval of old ones; they are two separate processes. They also realized that the hippocampus and the medial temporal lobes, both of the areas removed from Molaison, are the areas responsible for converting short term memory to long term memory.
These and similar studies had a number of important implications. The first is that certain cognitive processes (such as language) could be damaged separately from others, and so might be handled by distinct and independent cognitive and neural processes. (For more on the cognitive neuropsychological approach to language, see Eleanor Saffran, among others.) The second is that such processes might be localized to specific areas of the brain. Whilst both of these claims are still controversial to some degree, the influence led to a focus on brain injury as a potentially fruitful way of understanding the relationship between psychology and neuroscience.