The wavefunction is an inherent property of a particle (putting aside quantum field theory, which is even more fundamental). The wave function is not what we happen to know about a particle.
It's true that through measurement, we can narrow the range in space in which a particle must exist. But it is not correct to interpret that (and no physicist I know of does) to mean the particle was originally in that space and now we just know more about it. This is not just a philosophical/semantical issue. For example, in the double-slit experiment, if a particle really had a precise location before its location was measured, then it would not create the interference effects that show that the particle's truly probabilistic wavefunction goes through both slits. There are dozens of other experiments (e.g. Stern Gerlach) that clearly show the "now we just have more information" interpretation is wrong.
But I digress. What I wanted to write about was a question I've pondered. It is universally accepted among physicists that measurement changes the wavefunction of a particle. Measurement means something as simple as noticing there's a book on your desk (I am, in a real scientific sense, measuring the average position of the book's atoms), or as complicated as measuring the location of a photon exiting the slits of a double-slit experiment. Either one changes the world. But this measurement thing is mysterious, and it makes physics non-deterministic. We know how wavefunctions evolve over time, in the absence of "measurement." But if somebody "decides" to measure, that changes everything! There is no way to account for people "deciding" to measure.
Which brings up my question--is the "decision" to measure actually governed by physics as well? If you look at decision making as the result of physical interactions in the brain of an intelligent organism, then in a sense, the fact that measurements will be made in the future can be added into the quantum mechanical framework. This begs the fundamental question that physicists have wrestled with unsuccessfully for decades--what exactly is measurement? We know that human beings can collapse wavefunctions, disrupting their normal evolution and potentially drastically altering them. We just don't know how we do it, whether, say, a dog can do it, or whether we can "decide" to do it with some ability outside the realm of understood physics.
I know such talk can come across as gobbledy-gook, but I believe such questions are very real, very fundamental, and definitely fascinating.