The results of this evaluation suggest that reading times are mostly affected by local hierarchic structure, but the fact that GCG PCFG surprisal is able to provide a significant fit even in the presence of the PTB PCFG surprisal predictor suggests that some non-local information affects reading times.
while this evaluation showed that accumulated syntactic context is not generally a good predictor of reading times, some or all of the non-local information contained in the GCG categories is used by readers and so influences reading time durations over the local structural information reflected in the PTB PCFG surprisal measure.