Q: When does a human baby develop a consciousness? … Consciousness - the ability to sense the world around you in an independent way. You can think for yourself, and make choices that defy your natural instincts. It is what some say separates us from wild animals...
A: Consciousness is the term that has various meanings. In the above meaning, it requires the function of certain groups of neural circuits that include the ARAS (ascending reticular activating system), several cortical areas, and the thalamo-cortical loop [1,2]. So, for a fetus to begin to have consciousness, it must have these neural circuits developed to the point that they start functioning, which occurs around gestational week (GW) 24 -26. [3,4]
“Two of the most important pathways in the brain are the ones that transmit sensorimotor information, the thalamocortical (TC) and corticothalamic (CT) pathways. The TC relays sensory and motor information from the receptors in the retina, cochlea, muscle or skin to the sensorimotor regions of the neocortex via the major subcortical sensorimotor relay, the thalamus. The CT pathway completes the feedback loop by transmitting information from cortex back to the thalamus. These essential pathways begin to form in the later part of the second trimester in humans, and are complete by GW 26. ”
Studies about sleep-wake cycles in fetuses also find that a fetus has definite sleep-wake cycles with distinguishable REM and non-REM periods between GW 28 – 31 [5,6]. This means that a fetus does already have periods of wakefulness, which are necessary for conscious awareness to occur, instead of being in an unconscious state all the time, during this time. So, consciousness begins to exist in a fetus no later than this time period.
However, consciousness in a fetus is in a very rudimentary form; this can be evident from the fact that even an infant, which has a more mature brain than a fetus, exhibits consciousness only at a low level compared with an adult and that the default mode neural circuit, which is now found to have an important role in consciousness at rest , is still incomplete. What’s more, the sense of self or self-recognition begins to appear in some infants only around 15 months of age and in a majority of infants by 24 months of age . So, it’s very very unlikely that an infant has the sense of self and that it can think for/about itself.
In conclusion, it seems that an infant begins to have a rudimentary form of consciousness at around GW 24-26. This may help provide informed decision about legal abortion.
“Assuming that consciousness is mainly localized in the cortex, consciousness cannot emerge before 24 gestational weeks when the thalamocortical connections from the sense organs are established. Thus the limit of legal abortion at 22-24 weeks in many countries makes sense...”
However, these are only indirect evidence. Direct, definite evidence of when exactly a fetus begins to have consciousness is not available yet.
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