  Humans and animals recognize objects irrespective of the beholder's point of
view, which may drastically change their appearances. Artificial pattern
recognizers also strive to achieve this, e.g., through translational invariance
in convolutional neural networks (CNNs). However, both CNNs and vision
transformers (ViTs) perform very poorly on rotated inputs. Here we present
artificial mental rotation (AMR), a novel deep learning paradigm for dealing
with in-plane rotations inspired by the neuro-psychological concept of mental
rotation. Our simple AMR implementation works with all common CNN and ViT
architectures. We test it on ImageNet, Stanford Cars, and Oxford Pet. With a
top-1 error (averaged across datasets and architectures) of $0.743$, AMR
outperforms the current state of the art (rotational data augmentation, average
top-1 error of $0.626$) by $19\%$. We also easily transfer a trained AMR module
to a downstream task to improve the performance of a pre-trained semantic
segmentation model on rotated CoCo from $32.7$ to $55.2$ IoU.
