In a previous study, a new adaptive method (AM) was developed to adjust the learning rate in artificial neural networks:
the generalized no-decrease adaptive method (GNDAM). The GNDAM is fundamentally different from other traditional
AMs. Instead of using the derivative sign of a given weight to adjust its learning rate, this AM is based on a trial and
error heuristic where global learning rates are adjusted according to the error rates produced by two identical networks
using different learning rates. This AM was developed to solve a particular task: the orientation detection of an image
defined by texture (the texture task). This new task is also fundamentally different from other traditional ones since its
data set is infinite, each pattern is a template used to generate stimuli that the network learns to classify. In the previous
study, the GNDAM showed its strength over standard backpropagation for this particular task. The present study
compares this new AM to other traditional AMs on the texture task and other benchmark tasks. The results showed that
some AMs work well for some tasks while others work better for other tasks. However, all of them failed to achieve a
good performance on all tasks.
This study attempted to determine the influence of non-linear visual movements on our capacity to maintain postural control. An 8x8x8 foot CAVE immersive virtual environment was used. Body sway recordings were obtained for both head and lower back (lumbar 2-3) positions. The subjects were presented with visual stimuli for periods of 62.5 seconds. Subjects were asked to stand still on one foot while viewing stimuli consisting of multiplied sine waves generating movement undulation of a textured surface (waves moving in checkerboard pattern). Three wave amplitudes were tested: 4 feet, 2 feet, and 1 foot. Two viewing conditions were also used; observers looking at 36 inches in front of their feet; observers looking at a distance near the horizon. The results were compiled using an instability index and the data showed a profound and consistent effect of visual disturbances on postural balance in particular for the x (side-to-side) movement. We have demonstrated that non-linear visual distortions similar to those generated by progressive ophthalmic lenses of the kind used for presbyopia corrections, can generate significant postural instability. This instability is particularly evident for the side-to-side body movement and is most evident for the near viewing condition.