In perceptual learning, performance often improves within a short time if only one stimulus variant is presented, such as a line bisection stimulus with one outer-line-distance. However, performance stagnates if two bisection stimuli with two outer-line-distances are presented randomly interleaved. Recently, S. G. Kuai, J. Y. Zhang, S. A. Klein, D. M. Levi, and C. Yu, (2005) proposed that learning under roving conditions is impossible in general. Contrary to this proposition, we show here that perceptual learning with bisection stimuli under roving is possible with extensive training of 18000 trials. Despite this extensive training, the improvement of performance is still largely specific. Furthermore, this improvement of performance cannot be explained by an accommodation to stimulus uncertainty caused by roving.

#TheDress is remarkable in two aspects. First, there is a bimodal split of the population in the perception of the dress's colors (white/gold vs. black/blue). Second, whereas interobserver variance is high, intra-observer variance is low, i.e., the percept rarely switches in a given individual. There are two plausible routes of explanations: either one-shot learning during the first presentation of the image splits observers into two different, stable populations, or the differences are caused by stable traits of observers, such as different visual systems. Here, we hid large parts of the image by white occluders. The majority of naïve participants perceived the dress as black and blue. With black occluders, the majority of observers perceived the dress as white and gold. The percept did not change when we subsequently presented the full image, arguing for a crucial role of one-shot learning. Next, we investigated whether the first fixation determines the perceived color in naïve observers. We found no such effect. It remains thus a puzzling question where the source of variability in the different percepts comes from.

Ageing affects many visual functions. Here, we investigated the effects of ageing on vernier acuity and backward masking using the shine-through paradigm. We divided healthy older adults (>60 years) into two groups depending on whether vernier duration was comparable to younger adults (Older Adults 1) or not (Older Adults 2). Backward masking was deteriorated for Older Adults 2 but not for Older Adults 1. In addition, by using complex masking gratings, we found deficits in spatial and temporal vision in Older Adults 2, which cannot be explained by deteriorated visual acuity, pointing to cortical rather than retinal causes. Our results highlight the importance of taking into account individual differences in visual ageing research. In addition, our results have important implications for schizophrenia. Schizophrenia has been suggested to be a form of early brain ageing. Linking our current masking results in ageing to previous masking results in schizophrenia shows that schizophrenia is not a form of early ageing, at least not in the visual domain.

Here, we studied the time-based event expectancies in children with Autism spectrum disorder. Nine children with Autism spectrum disorders and ten (6-11 years) typically developing children participated. In a choice-response task with two different pre-target intervals, participants had to indicate the left or right direction of a target stimulus. The target was predicted by the duration of the pre-target interval with 80% validity. We found that, in children with Autism spectrum disorder, in contrast to typically developing children, the formation of time-based event expectancies was restricted to the relatively longer pre-target interval. This pattern is rather typical for healthy young adults. These findings indicate that children with Autism spectrum disorder are able to form time-based event expectancies, and that, similar to healthy young adults, longer pre-target intervals enable them to make more optimal temporal predictions.

We explored the perception of image focus in patients with cataracts, and how this perception changed following cataract removal and implantation of an intraocular lens. Thirty-three patients with immature senile cataract and with normal retinal function were tested before surgery and 2 days after surgery, with 18 of the patients retested again at 2 months following surgery. The subjective focus of natural images was quantified in each session by varying the slope of the image amplitude spectra. At each time, short-term adaptation to the spectral slope was also determined by repeating the measurements after exposure to images with blurred or sharpened spectra. Despite pronounced acuity deficits, before surgery images appeared “best-focused” when they were only slightly blurred, consistent with a strong compensation for the acuity losses. Post-operatively, the image slopes that were judged “in focus” before surgery appeared too sharp. This bias remained strong at 2 months, and was independent of the rapid blur after-effects induced by viewing filtered images. The focus settings tended to renormalize more rapidly in patients with higher post-operative acuity, while acuity differences were unrelated to the magnitude of the short-term blur aftereffects. Our results suggest that subjective judgments of image focus are largely compensated as cataracts develop, but potentially through a very long-term form of adaptation that results in persistent biases after the cataract is removed.