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The influence of partial occlusion on shape recognition
Humans are able to recognize objects from their outlines, largely irrespective of perspective, position and scale. Previous studies have drawn different conclusions regarding the importance of specific features such as curvature maxima in shape recognition. Schmidtmann et al. (2015) demonstrated that if observers were asked to match a segmented shape, which contained only either convex, concave curvature maxima or intermediate segments for varying lengths, to one of two subsequently presented re-scaled and re-positioned whole-contour shapes, they performed significantly better for convexities compared to the other shape features. Surprisingly, performance for convexities was independent of the length of the segments. These results implied that closed planar shapes are encoded using the positions of convexities, rather than concavities or intermediate regions, and that a simple shape-template model could explain performance (Schmidtmann et al., 2015, Scientific Reports, 5, 17142.).
In natural viewing conditions, however, objects are often partially occluded. To investigate the effect of partial occlusion, I employed the same paradigm and stimuli as previously (Schmidtmann et al. 2015), but occluded either 16.7%, 33% or 50% of the shape (i.e., only half the shape was visible in the 50% condition).
Results show that performance for convex features is superior to the other shape features and independent of segment length, replicating previous data. More importantly, however, recognition performance is only significantly impaired when 50% of the shape is occluded. These results demonstrate the importance of shape convexities for shape encoding, and the flexibility of the visual system to deal with partially occluded shapes.
https://ava2020meeting.wordpress.com
Schmidtmann, G., The influence of partial occlusion on shape recognition, AVA X-MAS Meeting 2020 [SLIDES]
In the blink of an eye: Reading mental states from briefly presented eye regions.
Faces provide not only cues to an individual's identity, age, gender, and ethnicity but also insight into their mental states. The aim was to investigate the temporal aspects of processing of facial expressions of complex mental states for very short presentation times ranging from 12.5 to 100 ms in a four-alternative forced choice paradigm based on Reading the Mind in the Eyes test. Results show that participants are able to recognise very subtle differences between facial expressions ; performance is better than chance, even for the shortest presentation time. Importantly, we show for the first time that observers can recognise these expressions based on information contained in the eye region only. These results support the hypothesis that the eye region plays a particularly important role in social interactions and that the expressions in the eyes are a rich source of information about other peoples’ mental states. When asked to what extent the observers guessed during the task, they significantly underestimated their ability to make correct decisions, yet perform better than chance, even for very brief presentation times. These results are particularly relevant in the light of the current COVID-19 pandemic and the associated wearing of face coverings.
Schmidtmann, G., Logan, A. J., Carbon, C. C., Loong, J. T., Gold, I. (2020). In the blink of an eye: Reading mental states from briefly presented eye regions. i-Perception, 11(5), 1–18. [PDF]
In the blink of an eye: Reading mental states from briefly presented eye regions.
Schmidtmann, G., Logan, A. J., Carbon, C. C., Loong, J. T., Gold, I. (2020). In the blink of an eye: Reading mental states from briefly presented eye regions. i-Perception, 11(5), 1–18. [PDF]
Faces provide not only cues to an individual's identity, age, gender, and ethnicity but also insight into their mental states. The aim was to investigate the temporal aspects of processing of facial expressions of complex mental states for very short presentation times ranging from 12.5 to 100 ms in a four-alternative forced choice paradigm based on Reading the Mind in the Eyes test. Results show that participants are able to recognise very subtle differences between facial expressions ; performance is better than chance, even for the shortest presentation time. Importantly, we show for the first time that observers can recognise these expressions based on information contained in the eye region only. These results support the hypothesis that the eye region plays a particularly important role in social interactions and that the expressions in the eyes are a rich source of information about other peoples’ mental states. When asked to what extent the observers guessed during the task, they significantly underestimated their ability to make correct decisions, yet perform better than chance, even for very brief presentation times. These results are particularly relevant in the light of the current COVID-19 pandemic and the associated wearing of face coverings.
Barhoom, H.S., Joshi, M.R., Schmidtmann G. (2020) The effect of response biases on resolution thresholds of Sloan letters in central and paracentral vision, BioRxiv, https://doi.org/10.1101/2020.09.04.283119
Clinical Vision Science - A Concise Guide to Numbers, Laws, and Formulas
This book provides a concise and user-friendly guide to the most common and important numbers, laws and formulas in clinical vision science. Clinicians and trainees in ophthalmology, optometry, orthoptics, and ophthalmic dispensing, who are seeking an easy-to-use lab coat pocket size resource, will find this book to be an essential reference in clinical practice.
Clinical Vision Science: A Concise Guide to Numbers, Laws, and Formulas is clearly structured into basics, physical optics, visual optics and ophthalmic lenses, optical instruments, photometry, visual perception, clinical procedures, and anatomy & binocular vision. Each chapter contains a range of tables, formulas, large illustrations and flow charts to allow readers to quickly and accurately find key facts for each type of examination procedure.
Vision Scientists!
With ARVO and VSS cancelled and most of us working from home and under strict social distancing guidelines, we would like to invite vision scientists worldwide to join us for a weekly vision science virtual coffee break.
Come and join us on Zoom next Wednesday, 25th March.
Topic: Vision Science in times of social distancing
Time: Mar 25, 2020 03:00 pm London
08:00 am Pacfic
11:00 am Eastern
03:00 pm UK
04:00 Central European
Join Zoom Meeting
https://unibas.zoom.us/j/661371046