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🔗 Cognitive science

Shepard tables (also known as the Shepard tabletop illusion) are an optical illusion first published in 1990 as "Turning the Tables," by Stanford psychologist Roger N. Shepard in his book Mind Sights, a collection of illusions that he had created. It is one of the most powerful optical illusions, typically creating length miscalculations of 20–25%.

To quote A Dictionary of Psychology, the Shepard table illusion makes "a pair of identical parallelograms representing the tops of two tables appear radically different" because our eyes decode them according to rules for three-dimensional objects.

This illusion is based on a drawing of two parallelograms, identical aside from a rotation of 90 degrees. When the parallelograms are presented as tabletops, however, we see them as objects in three-dimensional space. One "table" seems long and narrow, with its longer dimension receding into the distance. The other "table" looks almost square, because we interpret its shorter dimension as foreshortening. The MIT Encyclopedia of the Cognitive Sciences explains the illusion as an effect of "size and shape constancy [which] subjectively expand[s] the near-far dimension along the line of sight." It classifies Shepard tables as an example of a geometrical illusion, in the category of an "illusion of size."

According to Shepard, "any knowledge or understanding of the illusion we may gain at the intellectual level remains virtually powerless to diminish the magnitude of the illusion." Children diagnosed with autism spectrum disorder are less susceptible to the Shepard table illusion than typically developing children but are equally susceptible to the Ebbinghaus illusion.

Shepard had described an earlier, less-powerful version of the illusion in 1981 as the "parallelogram illusion" (Perceptual Organization, pp. 297–9). The illusion can also be constructed using identical trapezoids rather than identical parallelograms.

A variant of the Shepard tabletop illusion was named "Best Illusion of the Year" for 2009.

Christopher W. Tyler, among others, has done scholarly research on the illusion.

🔗 Cognitive science

Cognitive grammar is a cognitive approach to language developed by Ronald Langacker, which hypothesizes that grammar, semantics, and lexicon exist on a continuum instead of as separate processes altogether. This approach to language was one of the first projects of cognitive linguistics. In this system, grammar is not a formal system operating independently of meaning. Rather, grammar is itself meaningful and inextricable from semantics.

Construction grammar is a similar focus of cognitive approaches to grammar. While cognitive grammar emphasizes the study of the cognitive principles that give rise to linguistic organization, construction grammar aims to provide a more descriptively and formally detailed account of the linguistic units that comprise a particular language.

Langacker first explicates the system of cognitive grammar in his seminal, two-volume work Foundations of Cognitive Grammar. Volume one is titled "Theoretical Prerequisites", and it explores Langacker's hypothesis that grammar may be deconstructed into patterns that come together in order to represent concepts. This volume concentrates on the broad scope of language especially in terms of the relationship between grammar and semantics. Volume two is titled "Descriptive Application", as it moves beyond the first volume to elaborate on the ways in which Langacker's previously described theories may be applied. Langacker invites his reader to utilize the tools presented in Foundations' first volume in a wide range of, mainly English, grammatical situations.

🔗 Psychology 🔗 Cognitive science

Pandemonium architecture is a theory in cognitive science that describes how visual images are processed by the brain. It has applications in artificial intelligence and pattern recognition. The theory was developed by the artificial intelligence pioneer Oliver Selfridge in 1959. It describes the process of object recognition as a hierarchical system of detection and association by a metaphorical set of "demons" sending signals to each other. This model is now recognized as the basis of visual perception in cognitive science.

Pandemonium architecture arose in response to the inability of template matching theories to offer a biologically plausible explanation of the image constancy phenomenon. Contemporary researchers praise this architecture for its elegancy and creativity; that the idea of having multiple independent systems (e.g., feature detectors) working in parallel to address the image constancy phenomena of pattern recognition is powerful yet simple. The basic idea of the pandemonium architecture is that a pattern is first perceived in its parts before the "whole".

Pandemonium architecture was one of the first computational models in pattern recognition. Although not perfect, the pandemonium architecture influenced the development of modern connectionist, artificial intelligence, and word recognition models.

🔗 Cognitive science 🔗 Robotics

A cognitive architecture refers to both a theory about the structure of the human mind and to a computational instantiation of such a theory used in the fields of artificial intelligence (AI) and computational cognitive science. One of the main goals of a cognitive architecture is to summarize the various results of cognitive psychology in a comprehensive computer model. However, the results need to be formalized so far as they can be the basis of a computer program. The formalized models can be used to further refine a comprehensive theory of cognition, and more immediately, as a commercially usable model. Successful cognitive architectures include ACT-R (Adaptive Control of Thought - Rational) and SOAR.

The Institute for Creative Technologies defines cognitive architecture as: "hypothesis about the fixed structures that provide a mind, whether in natural or artificial systems, and how they work together – in conjunction with knowledge and skills embodied within the architecture – to yield intelligent behavior in a diversity of complex environments."