In prelabour, and the early phase of 1st stage, the woman is generally very present and aware. She will usually notice street noises, music being played or her toddler needing her attention. Some women will pay attention to tying up loose ends for work or around the house, pack their bag for hospital, or even consider giving the light fittings (with cobwebs on them) a clean!
As the woman moves into (or towards the end of) the active 1st phase, the intensity of her contractions increases and her focus will often naturally go inward, where her energy is needed. In most cases, the woman's awareness of what is happening around her lessens. Many women are no longer aware of their surroundings, and what's more they probably don't care! (Unless it is distracting them from focusing during a contraction.) This is why it can be annoying for someone to try and engage a labouring woman into conversation as it intensifies, especially during a contraction.
During the transitional phase, it can sometimes be hard to 'reach' the woman, because she has regressed into her own world. A few women will appear lost, others just unresponsive with little, to no, feedback. Many women describe this experience after the labour, as being acutely aware of everyone, and every conversation happening around them, but not actually engaging in it. This is often why 'small talk' over her can be upsetting, diminishing her importance, as she labours. Women also speak of having endless thoughts running through their minds, but not actually verbally expressing them. A little like being in a coma one would imagine. Just because she appears distant, doesn't mean she will not remember what has gone on around her and what everyone has said!