The Basic Ideas in Neural Networks (1994) [pdf]

I imagine that fields vary, but in the fields that I've worked in, the quality has gone down through the decades. Part of this is increasing pressure to publish, but another factor is the growth of fields. Growth works out very well if it is natural, with brilliant professors attracting brilliant students. But problems arise when deans and funding agencies judge professors by how many people they supervise. The pool of applicants has to be pretty deep, when professors are expected to supervise 3+ students each, and those students are expected to start doing the same after they graduate.

Many research fields come from nowhere, grow exponentially for a while, and then either decline or find a non-research way to reach a steady state (e.g. entertaining undergraduates in service classes). The early stages have high-quality work, or subsequent stages don't occur. But quality might be expected to decrease in those subsequent stages, simply because the people doing the work were not selected as much for their quality and the potential for success, but rather to keep flow going in an academic pipeline.

It also seems reasonable to put all of this in the larger context of declining levels of intellectual discourse and literacy through the years.

Geoff Hinton, some of who's work was in PDP, was an experimental psychologist by training.