Los reflejos arcaicos o primitivos, son responsables de la supervivencia en los primeros meses de la vida. El sistema nervioso central es el centro de control de todo el desarrollo (movimiento, aprendizaje y pensamiento). Los reflejos arcaicos inician su desarrollo en el momento de la concepción y siguen una secuencia regular y común para todos los seres humanos, a pesar de las diferencias culturales.Esta secuencia regular de los distintos estadios del desarrollo se identifica por patrones de movimiento que acontecen en cada etapa del crecimiento. Estos patrones se conocen como "reflejos arcaicos". Cada uno de ellos juega un papel necesario en el crecimiento del feto o del niño, y prepara el camino para el nuevo estadio. Los reflejos arcaicos son: \n* reflejos de supervivencia que ocurren de forma secuenciada en las primeras semanas del desarrollo fetal \n* Movimientos automáticos, estereotipados dirigidos por una parte muy primitiva del cerebro. Claro ejemplo es el reflejo de Moro \n* Ejecutados sin la implicación de los niveles superiores del cerebro \n* Idealmente tienen una vida corta y cuando su función se ha cumplido, son reemplazados por estructuras más sofisticadas (reflejos posturales) los cuales se controlan por el córtex \n* Son retenidos si no han cumplido sus funciones \n* Se consideran aberrantes y evidencian una inmadurez del sistema nervioso central si se presentan persistencia, si la intensidad es anormal o asimétrica o si reaparecen. Es el ejemplo del reflejo de Babinski

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Primitive reflexes are reflex actions originating in the central nervous system that are exhibited by normal infants, but not neurologically intact adults, in response to particular stimuli. These reflexes are absent due to the development of the frontal lobes as a child transitions normally into child development. These primitive reflexes are also called infantile, infant or newborn reflexes. Older children and adults with atypical neurology (e.g., people with cerebral palsy) may retain these reflexes and primitive reflexes may reappear in adults. Reappearance may be attributed to certain neurological conditions including, but not limited to, dementia (especially in a rare set of diseases called frontotemporal degenerations), traumatic lesions, and strokes. An individual with cerebral palsy and typical intelligence can learn to suppress these reflexes, but the reflex might resurface under certain conditions (i.e., during extreme startle reaction). Reflexes may also be limited to those areas affected by the atypical neurology, (i.e., individuals with cerebral palsy that only affects their legs retaining the Babinski reflex but having normal speech); for those individuals with hemiplegia, the reflex may be seen in the foot on the affected side only. Primitive reflexes are primarily tested with suspected brain injury for the purpose of assessing frontal lobe functioning. If they are not being suppressed properly they are called frontal release signs. Atypical primitive reflexes are also being researched as potential early warning signs of autistic spectrum disorders. Primitive reflexes are mediated by extrapyramidal functions, many of which are already present at birth. They are lost as the pyramidal tracts gain functionality with progressive myelination. They may reappear in adults or children with loss of function of the pyramidal system due to a variety of reasons. However with the advent of Amiel Tison method of neurological assessment, the importance of assessment of such reflexes in paediatric population has come down.

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