donderdag 23 december 2010
woensdag 22 december 2010
De-motivator of the day:
Eight year olds get published:
http://gawker.com/5715860/eight+year+olds-publish-study-in-respected-science-journal
dinsdag 21 december 2010
Infants and toddlers show enlarged visual sensitivity to nonaccidental compa...
Sent to you by Frouke via Google Reader:
via i-Perception by Pion on 12/20/10
Some shape changes are more important for object perception than others. We used a habituation paradigm to measure visual sensitivity to a nonaccidental shape change—that is, the transformation of a trapezium into a triangle and vice versa—and a metric shape change—that is, changing the aspect ratio of the shapes. Our data show that an enhanced perceptual sensitivity to the nonaccidental change is already present in infancy and remains stable into toddlerhood. We have thus established an example of how early visual perception deviates from the null hypothesis of representing similarity as a function of physical overlap between shapes, and does so in agreement with more cognitive, categorical demands.Things you can do from here:
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The shading cue in context. Johan Wagemans, Andrea J van Doorn, Jan J Koende...
Sent to you by Frouke via Google Reader:
via i-Perception by Pion on 12/21/10
The shading cue is supposed to be a major factor in monocular stereopsis. However, the hypothesis is hardly corroborated by available data. For instance, the conventional stimulus used in perception research, which involves a circular disk with monotonic luminance gradient on a uniform surround, is theoretically 'explained' by any quadric surface, including spherical caps or cups (the conventional response categories), cylindrical ruts or ridges, and saddle surfaces. Whereas cylindrical ruts or ridges are reported when the outline is changed from circular to square, saddle surfaces are never reported. We introduce a method that allows us to differentiate between such possible responses. We report observations on a number of variations of the conventional stimulus, including variations of shape and quality of the boundary, and contexts that allow the observer to infer illumination direction. We find strong and expected influences of outline shape, but, perhaps surprisingly, we fail to find any influence of context, and only partial influence of outline quality. Moreover, we report appreciable differences within the generic population. We trace some of the idiosyncrasies (as compared to shape from shading algorithms) of the human observer to generic properties of the environment, in particular the fact that many objects are limited in size and elliptically convex over most of their boundaries.Things you can do from here:
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donderdag 16 december 2010
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WBY-51JTYBV-1&_user=1394575&_coverDate=11%2F26%2F2010&_rdoc=13&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%236723%239999%23999999999%2399999%23FLA%23display%23Articles%29&_cdi=6723&_sort=d&_docanchor=&_ct=17&_acct=C000047079&_version=1&_urlVersion=0&_userid=1394575&md5=b75e7b854c3a1dff98adc629d19ee1e6&searchtype=a
ERP evidence of visualization at early stages of visual processing
Jonathan W. Pagea, Corresponding Author Contact Information, E-mail The
Corresponding Author, Paul Duhamelb and Michael A. Crognalec
a Department of Psychology, Minnesota State University, Mankato, MN, USA
b Department of Human Kinetics, Laurentian University, Sudbury, Ontario,
Canada
c Department of Psychology, University of Nevada, Reno, NV, USA
Accepted 1 November 2010.
Available online 26 November 2010.
Abstract
Recent neuroimaging research suggests that early visual processing
circuits are activated similarly during visualization and perception but
have not demonstrated that the cortical activity is similar in character.
We found functional equivalency in cortical activity by recording evoked
potentials while color and luminance patterns were viewed and while they
were visualized with the eyes closed. Cortical responses were found to be
different when imagining a color pattern vs. imagining a checkerboard
luminance pattern, but the same when imagining a color pattern (or
checkerboard pattern) vs. seeing the same pattern. This suggests that
early visual processing stages may play a dynamic role in internal image
generation, and further implies that visual imagery may modulate
perception.
--
Suggested reading by Ervin
http://app.psychonomic-journals.org/content/72/6/1510.abstract
Voluntary attention increases perceived spatial frequency
1. Jared Abrams,
2. Antoine Barbot and
3. Marisa Carrasco
New York University, New York, New York
Abstract
Voluntary covert attention selects relevant sensory information for
prioritized processing. The behavioral and neural consequences of such
selection have been extensively documented, but its phenomenology has
received little empirical investigation. Involuntary attention increases
perceived spatial frequency (Gobell & Carrasco, 2005), but involuntary
attention can differ from voluntary attention in its effects on
performance in tasks mediated by spatial resolution (Yeshurun, Montagna, &
Carrasco, 2008). Therefore, we ask whether voluntary attention affects the
subjective appearance of spatial frequency—a fundamental dimension of
visual perception underlying spatial resolution. We used a demanding rapid
serial visual presentation task to direct voluntary attention and measured
perceived spatial frequency at the attended and unattended locations.
Attention increased the perceived spatial frequency of suprathreshold
stimuli and also improved performance on a concurrent orientation
discrimination task. In the control experiment, we ruled out response bias
as an alternative account by using a lengthened interstimulus interval,
which allows observers to disengage attention from the cued location. In
contrast to the main experiment, the observers showed neither increased
perceived spatial frequency nor improved orientation discrimination at the
attended location. Thus, this study establishes that voluntary attention
increases perceived spatial frequency. This phenomenological consequence
links behavioral and neurophysiological studies on the effects of
attention.
--
Suggested reading by Ervin
http://www.journalofvision.org/content/10/12/27.abstract
What are the units of storage in visual working memory?
1. Daryl Fougnie
2. Christopher L. Asplund
3. René Marois
Abstract
An influential theory suggests that integrated objects, rather than
individual features, are the fundamental units that limit our capacity to
temporarily store visual information (S. J. Luck & E. K. Vogel, 1997).
Using a paradigm that independently estimates the number and precision of
items stored in working memory (W. Zhang & S. J. Luck, 2008), here we show
that the storage of features is not cost-free. The precision and number of
objects held in working memory was estimated when observers had to
remember either the color, the orientation, or both the color and
orientation of simple objects. We found that while the quantity of stored
objects was largely unaffected by increasing the number of features, the
precision of these representations dramatically decreased. Moreover, this
selective deterioration in object precision depended on the multiple
features being contained within the same objects. Such fidelity costs were
even observed with change detection paradigms when those paradigms placed
demands on the precision of the stored visual representations. Taken
together, these findings not only demonstrate that the maintenance of
integrated features is costly; they also suggest that objects and features
affect visual working memory capacity differently.
--
Suggested reading by Ervin
donderdag 2 december 2010
Identification of everyday objects on the basis of Gaborized outline version...
Sent to you by Frouke via Google Reader:
via i-Perception by Pion on 12/2/10
Using outlines derived from a widely used set of line drawings, we created stimuli geared towards the investigation of contour integration and texture segmentation using shapes of everyday objects. Each stimulus consisted of Gabor elements positioned and oriented curvilinearly along the outline of an object, embedded within a larger Gabor array of homogeneous density. We created six versions of the resulting Gaborized outline stimuli by varying the orientations of elements inside and outside the outline. Data from two experiments, in which participants attempted to identify the objects in the stimuli, provide norms for identifiability and name agreement, and show differences in identifiability between stimulus versions. While there was substantial variability between the individual objects in our stimulus set, further analyses suggest a number of stimulus properties which are generally predictive of identification performance. The stimuli and the accompanying normative data, both available on our website (http://www.gestaltrevision.be/sources/gaboroutlines), provide a useful tool to further investigate contour integration and texture segmentation in both normal and clinical populations, especially when top-down influences on these processes, such as the role of prior knowledge of familiar objects, are of main interest.Things you can do from here:
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