Longitudinal results show decreased spatial memory as a function of increased GPS use and reliance with time. Thirteen participants were retested three years after initial testing. We investigated the change in navigational variables between pre and post-testing, covarying with performance and lifetime GPS experience at baseline. Note that the graphs show plotted residuals from the partial correlations, where covariates were regressed out of the variables of interest. For example, although the ‘Hours of GPS use since pre-test’ variable takes on negative values in the graphs, all original (unregressed) datapoints are in the positive range because all participants used GPS over the three-year period. (A) In the CSDLT, there is a significant negative correlation between hours of GPS use since pre-test and post-pre performance on the second probe trial, r = −0.68, Bootstrap BCa 95% CI [−0.91, −0.10]. (B) There is also a significant negative correlation between post-pre GPS reliance scores and post-pre performance on the second CSDLT probe trial, r = −0.47, Bootstrap BCa 95% CI [−0.75, −0.28]. (C) There is a significant negative correlation between post-pre GPS reliance scores and the number of trials required to reach the learning criterion of the CSDLT, r = 0.62, Bootstrap BCa 95% CI [0.18, 0.91], suggesting that more frequent reliance on GPS in various situations leads to greater difficulty in learning the location of objects. (D) On the 4/8 VM, there is a significant negative correlation between hours of GPS use since pre-test and post-pre map drawing scores, r = −0.52, Bootstrap BCa 95% CI [−0.79, −0.21], indicating that GPS use leads to a lower ability to form cognitive maps. (E) There is a significant negative correlation between hours of GPS use since pre-test and post-pre average number of landmarks used, r = −0.32, Bootstrap BCa 95% CI [−0.68, −0.05] as well as (F) a significant negative correlation between post-pre GPS reliance scores and the post-pre number of landmarks noticed in the environment, r = −0.67, Bootstrap BCa 95% CI [−0.90, −0.07], indicating that increased GPS use leads to decreased landmark encoding.