Workshop on Perception: Reality and Illusions


Sponsored by the Interdisciplinary Program in Cognitive Science, Georgetown University


9:00 Introduction: David Lightfoot, Department of Linguistics, Georgetown University

9:15 Spatial Metamers: Illusion and Disillusion in Virtual Space
William Warren, Department of Cognitive and Linguistic Sciences, Brown
All "illusions" come with assumptions about the proper objects of perception and cognition. In spatial cognition, it is often assumed that we learn a Euclidean cognitive map of our environment. Yet humans navigating a virtual environment fail to notice large distortions of space, as if they can’t distinguish many possible worlds or “spatial metamers.” But if we understand that the function of this system is to learn the topological structure of the environment, then navigation is robust -- and we are dis-illusioned.

10:15 Seeing into the Future: How Anticipated Action Influences Spatial Perception
Jessica Witt, Department of Psychological Sciences, Purdue University
The action-specific account of perception proposes that perceivers see the world in terms of their ability to act. For example, softball players who are hitting better than others see the ball as bigger. Targets within reach as the result of having a reach-extending tool look closer than when the tool is not used to reach. Objects that are easier to block look like they are moving slower than when they are more difficult to block. These examples illustrate that perception is sensitive to the perceiver’s ability to act. The action-specific perception account challenges many traditional and mainstream theories of perception which presume that the same physical environment, which gives rise to the same optical information received by the eye, should therefore look the same and should not be influenced by the perceiver’s action capabilities. Instead, the action-specific perception account proposes that perception expresses the relationship between the perceiver and the environment. Whereas multiple relationships exist between the perceiver and the environment, only some of these relationships are expressed in perception and the relationships that are expressed depend on the perceiver’s intention to act.

11:15 Sleights of Mind: What the Neuroscience of Magic Reveals About our Brains
Susana Martinez-Conde and Stephen Macknik, Barrow Neurological Institute. 
All our life, every object we see, every person we know and every incident we experience, are derived from brain processes, and not necessarily the result of an event in the real world. The same neural machinery that interprets the sensory inputs also creates our thoughts, imaginations and dreams; thus the world we experience and the world we imagine have the same physical bases in the brain. Just as physicists study the minutest subatomic particles and the largest galactic conglomerates to understand the universe, neuroscientists must examine the cerebral processes underlying perception to understand our experience of the universe. Visual illusions are one of our most important tools to understand how the brain builds our experience of reality. Likewise, the principles developed by magicians and illusionists throughout history can be very useful to manipulate attention and awareness in the laboratory. Here we will discuss how the visual and cognitive illusions developed by artists and magicians can be applied to the study of the neural bases of consciousness and perception.

12:15 Lunch, RSVP

1:00 Complex Analogies Lurking Behind the Scenes of Our Mundane Errors
Douglas Hofstadter, College of Arts and Sciences Distinguished Professor of Cognitive Science and Comparative Literature, Indiana University
Though errors are among the most common features of human behavior, they seldom strike us as being of interest. Indeed,typical explanations for an error just made are bland statements such as, "I was just tired", or "Gee, I guess I was confused". While these clichéd "explanations" may have some truth to them, they shed no light on what was going on inside the person's head -- they just restate the fact that an error was made. One can certainly make much more insightful remarks about what must have been going on in the error-maker's brain. Careful consideration of the hidden processes taking place "down there" in the churning ocean of subcognitive activity opens up profound questions about the relations between different levels of brain activity.

I will present a sampler of errors and will discuss the underlying mental processes. The most central process will turn out to be the creation of analogies -- rapid-fire, almost always unconscious, and often very subtle.

2:00 Linguistic Illusions: Where You See Them, Where You Don't
Collin Phillips, Professor of Linguistics, University of Maryland
Just as optical illusions help to reveal the inner workings of the visual system, linguistic illusions can be similarly revealing about how humans mentally perceive and encode language. Linguistic illusions are situations where people systematically mis-interpret, mis-hear, or mis-judge sounds, words, or sentences, arriving at interpretations that are unintended, or perceiving ungrammatical sentences as if they are well formed. Importantly, linguistic illusions are not simply the product of a human language system that is uniformly unreliable or gullible: speakers show impressive sensitivity in many domains, which makes the illusions all the more striking.

3:00 Neural Mechanisms of Object Recognition in the Cortex: From Pipelines to Flying Crossbodies
Maximilian Riesenhuber, Department of Neuroscience, Georgetown University Medical Center
Object recognition is a fundamental cognitive task that we perform countless times every day – such as right now when reading the words in this abstract. Yet, despite the apparent ease with which we see, object recognition is a very difficult computational problem. It is even more difficult from a biological perspective, since it involves several levels of understanding, from the level of cellular and biophysical mechanisms up to the level of brain systems and behavior. Recent results from human neuroimaging, EEG, and computational modeling covering areas as varied as face perception, reading, car categorization and even phoneme processing, suggest an appealingly simple yet powerful unified account of how our brains make sense of the world based on one wave of activity through the sensory system to frontal cortex.