Associate Professor, Psychology
Associate Professor, Computer Science
Douglas T. Kenny Building
2136 West Mall
Vancouver, BC V6T 1Z4
Canada

Other than directing the UBC Visual Cognition Lab, Dr. Rensink is also an integral part of the Imager Lab, the Vancouver Institute for Visual Analytics (VIVA), and the Cognitive Systems program. His primary interests are in computational/human vision and data visualization.

I am interested in vision—the various ways that humans, animals, and computers use light to see.  I believe that vision involves constraints that apply to any  system, and that the most successful visual systems are based on very general information-processing strategies.  As such, my approach is to examine biological systems (including humans) to see how they operate, and then to look at these mechanisms from a computational point of view to see if they embody more general principles.  Among other things, these more general principles can provide a scientific basis for the design of visual interfaces that can interact with human visual systems in an optimal way.

My research interests include:

1. Human vision

  • what is attention, and how does it operate?
  • what is space, and how do we represent it?
  • what are objects, and how do we represent them?
  • how are scenes represented?

2. Computational vision

  • how do “quick and dirty” processes reduce time requirements?
  • what are the trade-offs for various kinds of representations?
  • what are the physical limits of visual perception?
  • are there universal principles for all vision systems?

3. Information visualization

  • what is the basis of effective design in visual displays?
  • how can visual interfaces be designed so as to be “transparent” to the user?
  • how can data be represented so that our visual intelligence can pick out interesting patterns?
  • how can visual analytics systems be designed to allow the user to easily analyze immense amounts of data?

 

 

 

1. Change blindness.  This phenomenon is a striking inability of observers to notice large changes in visual stimuli whenever the change is made the same time as a transient motion elsewhere.  Originally encountered by researchers who found that large changes could go unnoticed if made during eye movements and film cuts, I helped to discover that the cause was much more general–namely that attention is needed to see change.  This was done by the development of a “flicker paradigm”, in which an original and changed image continually alternated, with a brief blank interval between them.  Under these conditions subjects have a very difficult time seeing the change between the two pictures, even when the changes are large, and the subjects are expecting them. Evidently, attention is required to see change; without it, people will look at but not see the change.
This phenomenon challenges the idea that vision involves building up an internal picture in our heads; instead, much more dynamic representations must be used.  Also, given that attention is needed to see change, change blindness can be used as a new source of information about the nature of visual attention.    (Take a look at some examples of this effect!)

 

2. Intelligent rapid processing.  Until recently, it was believed that the rapid “preattentive” processing at early levels of vision was obtained by reducing the complexity of the operations, i.e., only simple tasks–such as determining orientation or color–could be done quickly.  However, work I did (with Jim Enns and Patrick Cavanagh) shows that the preattentive system is capable of much more. For example, it can recover properties of the scene, such as three-dimensional orientation and lighting direction.  It can also carry out grouping, and can rapidly identify shadows and highlights.  In my PhD thesis, I developed a computational account of how such “intelligent” processing could obtain speed by reducing reliability slightly.  In other words, much of preattentive processing has a quick and dirty nature; even though the processes will not succeed under all conditions, they will do so often enough.

 

3. Information Visualization.  This work investigates how information visualizations work.  Among other things, I applied classical measurement techniques used in visual psychophysics to displays used for information visualization (e.g. scatterplots). Results (presented at both VSS 2010 and EUROVIS 2010) show a highly linear/logarithmic behaviour (basically, the Weber and Fechner laws).  At a practical level, this allows various designs to be evaluated quickly and rigorously.  At a theoretical level, it shows that the early visual system is even more intelligent than people think. Work is also underway on testing new kinds of scatterplot designs that work as well as existing ones, but use far less space.
These results open up the prospect of considering visualizations as interesting stimuli for vision scientists. Similarly, it opens up the prospect of researchers in information visualization adopting a new (and more rigorous) set of tools. If these developments proceed, it will create a seamless link between workers in these two fields, which have previously remained somewhat separate.

 

4. The Science of Magic.  During the past few years I (along with Gustav Kuhn and my former students Alym Amlani and Jay Olson) have investigated how magic effects work. This includes the way magicians direct the attention of observers, and the way that magicians can give observers the illusion of free will. This approach has received considerable interest in the press, including a segment on CBC (Project X). A paper on this topic appeared in Trends in Cognitive Sciences in 2008, and another in Perception in 2012.

 

5. Mindsight.  Recently, I discovered that observers could sense a change, but not see it (i.e., have a visual experience of it) for several seconds.  Essentially, observers can reliably feel “in their gut” that something is happening, even though they have no visual experience of it.  (It should be pointed out that this effect is still mediated visually–the signal must still come in through the eyes.)  In a way, this effect is similar to blindsight, except that (a) the experience is still a conscious one of “something happening”, and (b) it is obtained from normal observers rather than patients with lesions.  It may be that this effect corresponds to what is commonly believed to be the “sixth sense”.