Media

Psychologists at HKU discover “falling＂skyscrapers in Hong Kong

12 Jul 2013

 

For long, Peak Tram riders enjoy the beautiful scenery of skyscrapers on the steep hillside of Victoria Peak. The view is in fact “deceptive”, according to a team of researchers from the University of Hong Kong (HKU).

Don’t fret! The buildings in the city are all intact and aren’t actually falling – Researchers from HKU Psychology Department discovered an illusion on the Peak Tram in which the buildings appear to tilt away from the observers when they are looking towards the Peak.  They observed that the illusory effect is stronger at night compared to the day. The research paper has been published in one of the most prestigious journals, Psychological Science of the Association of Psychological Science.

The HKU researchers, Assistant Professor Dr. Chia-huei Tseng and her team from the Psychology Department, have identified several possible causes behind the Peak Tram illusion through various experiments conducted repeatedly.   There are two main factors influencing the strength of the illusion – visual cues and non-visual cues. As for visual cues, it is suggested that the window frames might have given a frame of reference which could have contributed to the illusion. Thus to eliminate this, observers participating in the experiments wore a headgear with a small circle to look through, in which the window frames were not visible to the observer. With the headgear on, the illusory effect was reduced.

As for non-visual cues, the position of the observer affected the strength of illusion. For instance, if the observer stood throughout the ride instead of sitting down, the perceived tilt was not as great. This can be accounted for by the fact that the gravity sensors in our ankles take in information from various directions in order to judge our body orientation relative to gravity.

Furthermore, observers leaned and sat against different wedges can reduce the illusory effect. This is because tactile information given off from our backs and buttocks could be helpful in judging our body orientation and thereby affecting the Peak Tram illusion. It is worth noting, however, that these mentioned alterations using the wedges did not have much influence on the illusion individually; but when all were used simultaneously, the illusion was greatly diminished. In other words, the whole is greater than the sum of its parts!

This illusion signifies our still have very limited understanding of how our brains perceive verticality,  and how we interact with the world around us. Professor Shinsuke Shimojo from California Institute of Technology, who has helped build “tilted rooms” in science museums to demonstrate how our sense of vertical world can be easily distorted, said,  “On top of its pure scientific contribution to the field, [the research] does have a merit to draw scientists’ and students’ attention to real-world perceptual phenomena, and to open up various possibilities of field experiment, partly owing to the fact that the case dealt here is a famous sightseeing place in Hong Kong.”

Researchers are sometimes given the stereotype of being hermit-like, where they stay indoors in lab cubicles to study various phenomena. However, this study is extremely interesting and baffling because for one, it challenges this misconception that research is limited to ‘scientific settings’ indoors, and more importantly, the illusion is something anybody can observe in the environment – all you need is to ride the Peak Tram! Professor Frans Verstraten, president of the Vision Sciences Society and the McCaughey Chair of Psychology at the University of Sydney said, "One complaint that vision scientists often hear is that their experiments are being performed using computers in dark rooms, where the results may not be easy to generalise to the world we actually live in.

You might be thinking: “Now that you’ve spoiled the illusion for me, I won’t be able to experience it.” Don’t worry – even after the countless rides on the tram, the illusion never fails to create the amazement. Each and every ride, our brain manages to play tricks on the brains and allow the passengers to perceive falling skyscrapers without fail.

Summer holiday is just around the corner, and many of you may have visitors coming to Hong Kong and the Peak is one of the prime locations for tourists and locals alike. So why don’t you fall in line to watch the “falling skyscrapers” on the Peak this summer?

For press enquiry, please contact:
Rhea Leung, Manager (Media) Communications and Public Affairs Office,
at 2857 8555 / 9022 7446 or rhea.leung@hku.hk
Assistant Professor Chia-huei Tseng, Department of Psychology
at 3917-8043  or  tseng@hku.hk