The First Response is the value of the first vowel of the first name, and it is the narrowest input in the chart. Every other position sums something. This one reads a single letter.
That gives it a distinctive property: it takes only a handful of values in practice. A, E, I, O and U are worth one, five, nine, six and three, so most people in an English-speaking population have a First Response of one, five or six, and the position cannot discriminate finely no matter how many people it is applied to. Anyone whose first name begins with a consonant cluster and then an a, which is a large share of common names, gets the same figure.
The reading attached to it is correspondingly narrow. Practitioners use it for the immediate reflex, what a person does in the first second of a surprise, before the rest of the chart has time to operate. That is a smaller claim than most positions make and it is at least consistent with the size of the input.
The Y question bites here in an unusually direct way, since a name such as Lyle has no vowel before the y at all, and the sources this atlas cites for the chart do not agree on what to do. So does the question of which name is first, in the many naming conventions where the family name precedes the personal one.
It is the position most obviously vulnerable to a change of spelling, and the one practitioners weight least.