Serial dependence : systemic bias towards recent past experience

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When we pass through an art gallery, what determines our idea of beauty?

A University of Sydney study of how people rate the aesthetics of each artwork shows part of our aesthetic assessment is due to the painting you saw a few moments before.

The research, led by PhD student Ms Sujin Kim in the School of Psychology, is published in the Journal of Vision. 

It shows that we don’t appreciate every painting in isolation. Instead, we carry a bias from the artwork just seen.

This bias is not the contrast effect you might intuitively think. A beautiful painting does not make the next one look less attractive but makes it more attractive.

The study, completed under the supervision of Professor David Alais from the University of Sydney and Professor David Burr from the University of Florence, Italy, involved presenting a sequence of 40 paintings to 24 observers who were asked to rate each one using a slider to indicate how aesthetically appealing or attractive it was. The paintings were depicting scenery or still life.

“While it is often said that beauty is in the eye of the beholder, this is not the whole story – it partly depends on what was recently seen,” Professor Alais said.

The first question the 24 observers were asked to respond to was whether they rated each painting independently of what they had just seen. To do this, the sequence was presented 20 times with each run having a different random order. In this way, a given painting was rated 20 times, but with a different random sequence preceding it. The data was clear: observers don’t rate each painting consistently but are biased by what they just saw.

This shows a woman looking at paintings in a gallery

This bias is not the contrast effect you might intuitively think. A beautiful painting does not make the next one look less attractive but makes it more attractive. The image is in the public domain.

“Many people naively suppose a kind of ‘contrast effect’ whereby a painting may look more attractive if it follows an unattractive painting,” Professor Alais said. “The surprising result was that the bias was a positive one: paintings were rated higher following an attractive painting, or lower, following unattractive ones.”

The research refers to this effect as “serial dependence”, which describes a systemic bias towards recent past experience. Previous studies have found, many stimulus attributes – including orientation, numerosity, facial expression and attractiveness, and perceived slimness – are systematically biased towards recent past experience. “Perhaps art curators have known all along about the bias towards the recent past,” Professor Alais said.

“They often keep the best pieces for last and build up to it. Our study shows this would ensure an accumulating effect and guarantee a big finish.”


A crucial function of vision is detecting important changes in the environment, and sensory adaptation aids in maximizing sensitivity to change. The visual system adapts to properties such as color, orientation, object and scene properties, and many others1,2, thereby optimizing how it responds to changes in these attributes35.

Adaptation is a simple but powerful mechanism for leveraging past visual input to maximize change sensitivity, but there is a flip side to the coin: the physical world is largely stable and continuous over time.

Objects, scenes, and physical properties tend to persist over time, making the recent past a good predictor of the present6.

The visual system may therefore delicately balance the need to optimize sensitivity to image changes with the desire to capitalize on the temporal continuity of the physical environment. It may often be advantageous to assume that the present visual environment is similar to the one seen moments ago.

One means of combating noise and stabilizing visual estimates would be to introduce serial dependence to visual perception, to systematically bias perception at the present moment toward input from the recent past.

The information necessary for such serial dependence to occur may be retained by the visual system—observers can maintain precise information about basic visual features over long delays7, sometimes even in the face of intervening stimuli8.

However, the existence of such a memory trace does not necessarily imply that it alters the perception of future stimuli or that serial dependence occurs in perception. Indeed, maximally independent perception from one moment to the next would carry its own advantages, for example in reducing systematic biases over time. Further, given the known benefits of adaptation and ubiquitous negative aftereffects5, it may be that negative aftereffects dominate over any positive serial dependence in perception.

While serially dependent perception would be a simple means of capitalizing on the continuity of the physical environment, whether such an effect actually arises in perception remains to be tested.

Here we tested for serial dependence in visual perception using an orientation judgment task. Subjects viewed a series of randomly oriented gratings presented several seconds apart in time and reported the perceived orientation of each grating using an adjustment response.

We found that perceived orientation is strongly and systematically attracted toward orientations seen over the last several seconds.

This perceptual serial dependence is modulated by attention and is spatially tuned, occurring more strongly for successive stimuli that appear nearby in space.

Several control experiments demonstrate that the perceptual serial dependence we report cannot be explained by any known effect of priming, hysteresis, explicit memory, or expectation.

Our results reveal a systematic influence of recent visual input on orientation perception at any given moment: perceived orientation, even of unambiguous stimuli, is attracted toward visual input from the recent past.


Source:
University of Sydney
Media Contacts:
Elissa Blake – University of Sydney
Image Source:
The image is in the public domain.

Original Research: Open access
“Attraction to the recent past in aesthetic judgments: A positive serial dependence for rating artwork”. Sujin Kim; David Burr; David Alais.
Journal of Vision doi:10.1167/19.12.19.

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