Perceptual Learning With Only One Stimulus

Perceptual learning is learning to see. For example in a bisection task, three parallel lines are presented with the central line slightly offset towards the right or the left outer line. Participants indicate the offset direction. Training gradually improves performance. Models of perceptual learning explain learning by synaptic changes determined by the learning algorithm and the stimulus presentation. In these models, learning cannot occur when the very same stimulus is presented in all training trials. Here we show that, surprisingly, humans can improve performance in such "impossible" conditions. We trained observers with a line bisection task where the central line was always exactly in the middle for all 4160 training trials. Participants were not told about the “zero offset” and were instructed to indicate the offset direction as in a normal bisection task. Surprisingly, performance improved with gains similar to "normal" bisection experiments where both the left and right offset are presented. These results cannot be explained by most of current models of perceptual learning and reproduce previous studies in the auditory domain (Amitay, Irwin & Moore 2006). We suggest that perceptual learning occurs by mental imagery in accordance with previous results (Tartaglia, Bamert, Mast & Herzog, 2009, 2012).

Perceptual Learning With Indiscriminable Stimuli

Lukasz Grzeczkowski, Fred Mast, Elisa Tartaglia

Perceptual learning is learning to perceive. For example, in a bisection task three parallel lines are presented. The central line is slightly offset towards the right or the left outer line. Observers indicate the offset direction. Training greatly improves performance. In models of perceptual learning, learning occurs by synaptic changes determined by the learning algorithm and the stimulus presentation. None of the models can learn when the very same stimulus is presented during training. Here we show that, surprisingly, humans can improve performance in such "impossible" conditions. We trained observers with a line bisection task where the central line was always exactly in the middle, i.e., the stimulus was the same in all 4160 trials. Participants were not told about the zero offset and were instructed to indicate the offset direction as in a normal bisection task. Surprisingly, performance improved with gains similar to "normal" bisection experiments where both the left and right offset are presented. These results cannot be explained by most of current models of perceptual learning and reproduce previous studies in the auditory domain (Amitay, Irwin & Moore 2006). We suggest that learning occurs by mental imagery in accordance with previous results (Tartaglia, Bamert, Mast & Herzog, 2009, 2012).

2014

Linking perceptual learning with identical stimuli to imagery perceptual learning

Lukasz Grzeczkowski, Michael Herzog, Fred Mast, Elisa Tartaglia

Perceptual learning is usually thought to be exclusively driven by the stimuli presented during training (and the underlying synaptic learning rules). In some way, we are slaves of our visual experiences. However, learning can occur even when no stimuli are presented at all. For example, Gabor contrast detection improves when only a blank screen is presented and observers are asked to imagine Gabor patches. Likewise, performance improves when observers are asked to imagine the non-existing central line of a bisection stimulus to be offset either to the right or left. Hence, performance can improve without stimulus presentation. As shown in the auditory domain, performance can also improve when the very same stimulus is presented in all learning trials and observers were asked to discriminate differences which do not exist (observers were not told about the set up). Classic models of perceptual learning cannot handle these situations since they need proper stimulus presentation, i.e., variance in the stimuli, such as a left vs. right offset in the bisection stimulus. Here, we show that perceptual learning with identical stimuli occurs in the visual domain, too. Second, we linked the two paradigms by telling observers that only the very same bisection stimulus was presented in all trials and asked them to imagine the central line to be offset either to the left or right. As in imagery learning, performance improved.

Association for Research in Vision and Ophthalmology2015

Human perceptual learning by mental imagery

Laura Bamert, Michael Herzog, Fred Mast, Elisa Tartaglia

Perceptual learning is learning to perceive. For example, a radiologist is able to easily identify anomalies in medical images only after extended training. Theoretical and psychophysical studies [1-12] suggest that such improvements of performance are accomplished by neural synaptic changes driven by the repetitive presentation of stimuli. Here, we demonstrate that an equally reliable improvement can also occur in the absence of physical stimulation. Imagining the crucial part of a bisection stimulus was sufficient for successful perceptual learning. Hence, the neural processes underlying perceptual learning, which are usually assumed to be primarily dependent on stimulus processing, can be equally based on mentally generated signals.

Elsevier2009