Neurophilosophy

Desire influences visual perception

WE tend to assume that we see our surroundings as they really are, and that our perception of reality is accurate. In fact, what we perceive is merely a neural representation of the world, the brain’s best guess of its environment, based on a very limited amount of available information. This is perhaps best demonstrated by visual illusions, in which there is a mismatch between our perception of the stimulus and objective reality.

Even when looking at everyday objects, our perceptions can be deceiving. According to the New Look approach, first propounded in the 1940s by the influential cognitive psychologist Jerome Bruner, perception is largely a constructive process influenced by our needs and values. Recent research has provided some evidence for this: in 2006, psychologists Emily Balcetis and David Dunning, then at Cornell University, reported that an ambiguous figure tended to be interpreted according to the self-interest of the perceiver. They now show that the desirability of an object influences its perceived distance.

In the new study, 90 undergraduates were made to sit at a table across from a full bottle of water. Half of the participants were randomly assigned to the “thirsty” condition, and given a serving of pretzels to eat. The rest were placed in the “quenched” condition, and told that they could drink as much of the water as they wanted. Both groups were asked to indicate how long it had been since they last had a drink, how thirsty they were and how appealing the bottle of water was. Finally, they were shown a 1-inch line as a reference, and asked to estimate the distance between their own position and the water bottle.

The participants who had been given pretzels to eat during the experiment reported feeling thirstier than those who drank the water, as would be expected. They also rated the bottle of water as being more desirable, and estimated the distance between themselves and the bottle to be smaller than did the quenched participants. Their state of thirst had influenced their perception of distance, such that the water bottle was perceived to be closer than it actually was. 

That the thirsty participants found the bottle of water to be more desirable is not at all surprising – water will quench their thirst, and therefore has immediate physiological benefits. But how about objects that are desirable because of their social value? To investigate this, Balcetis and Dunning asked another set of students to estimate their distance from a $100 bill. One group was told that they could win the money in a simple card game; the other was told that the bill belonged to the experimenter. In this case, the first group find the money more desirable than the first. Again, both groups were asked to estimate their distance from the object in question and again, those who had been told they could win the $100 bill reported it as being closer than those who were told it belonged to the experimenter.

The researchers then asked a third set of participants to complete a survey, and told that it had been designed to assess their sense of humour. Each then watched as their response was graded; half of them were told that their sense of humour was “above average”, and the other half were told that theirs was “below average”. The surveys were then clipped to a stand, and each participant was asked to estimate how far away it was. Those given positive feedback estimated the stand to be closer than those negative feedback.

A perceptual test which did not require a numerical response was then performed. Participants were asked to throw a small rubber bean bag towards a gift voucher placed on the floor in front of them, and told that the person whose toss landed closest to the voucher would win it. One group was told that the voucher had a value of $25, thus making it desirable to them, while the other was led to believe that it was worthless. This experiment confirmed the earlier ones – those participants who believed the voucher was worth something perceived it to be nearer, and consequently underthrew the bean bag so that it fell short of the target.

The researchers designed one final experiment to rule out the possibility that desirable objects are perceived tobe closer because they evoke a strong emotionalresponse. Participants stood opposite a wall onto which two pieces of tape had been stuck. An object was placed onto a table standing beneath the tape. One group saw a brightly packaged box of chocolates, and the other saw a plastic bag which they were told contained a freshly collected sample of dog faeces. (Both chocolate and faece sevoke strong emotionalresponses.) The participants were then asked to move toward or away from the wall until their distance from it matched that between the two pieces of tape. This time, those shown the chocolate moved further away from the wall than those shown the plastic bag. This seems paradoxical, but is easily explained – the chocolate was perceived to be closer than the faeces because it is the more desirable of the two objects, and so the participants compensate for this by moving further back from it.

These findings demonstrate that higher order psychological states can have a significant effect on visual perception. Specifically, they show that our desires have a direct influence on the perception of distance, such that desirable objects are perceived to be closer than they really are. This mechanism would serve to guide behaviour in the optimum way, by encouraging the perceiver to reach out and acquire the desired object. Further research into this effect is needed, however, as there are other situations in which the opposite could plausibly occur. Undesirable objects which might pose a threat – such as a venomous snake, for example – might also be perceived as being closer than they are so that one can escape quickly.

Related:


Balcetis, E., & Dunning, D. (2009). Wishful Seeing: More Desired Objects Are Seen as Closer Psychological Science. DOI: 10.1177/0956797609356283.

Balcetis, E. & Dunning, D. (2006). See What You Want to See: Motivational Influences on Visual Perception. J. Pers. Soc. Psych. 91: 612-625. [PDF]

Comments

  1. #1 Dan
    January 9, 2010

    Very interesting. For those of us without access to the original research, can you give a sense of how dramatic the numbers are? Is this a subtle effect that shakes out statistically from large samples, or something dramatic and observable at human scale? Either way it’s fascinating and thought-provoking. Thanks for the coverage!

  2. #2 Scientific Chick
    January 9, 2010

    Just discovered this blog, and your interesting selection of topics appeals to the neuroscientist in me. :)

    So if something is desirable, we perceive it to be more attainable. Somehow that doesn’t fit with the idea of graduating.

    Great post!

  3. #3 mjt
    January 10, 2010

    Most interesting for a person, psychologically prone, who likes reading these sorts of articles to understand better with human behaviour and cope with it.

  4. #4 Andrew
    January 10, 2010

    Fantastic research. But, the title is somewhat misleading. The results of these experiments show a correlation between judged distance (expressed in a variety of ways) and desires, but additional research is needed to show that the perceptions themselves change. The conclusion is underdetermined by the available evidence insofar as the causal processes related to desirability may be up stream or down stream from the neural correlates of consciousness.

  5. #5 Mo
    January 10, 2010

    @Dan: In the first experiment, thirsty participants perceived the water bottle to be an average of 3 inches closer than quenched participants. In the second, estimates from those who thought they could win the $100 bill were on average 8″ shorter than those who thought it belonged to the experimenter. For the survey, those given positive feedback perceived the survey to be an average of 7″ closer than those given negative feedback. The bean bag was underthrown by an average of 9″ by those who thought the voucher was worth something; the other group overthrew by an average of about 1″. In the last experiment, those who saw the chocolate stood an average of 14″ further away from the wall than the other group.

  6. #6 Dan
    January 10, 2010

    @Mo: Thanks for the info!

  7. #7 Ewan R
    January 11, 2010

    I wonder if this in any way accounts for otherwise highly skilled sporting professionals completely fluffing their roles in high impact games (playoffs etc) – I’m looking at you Matt Holliday.

  8. #8 shan
    January 11, 2010

    I think motivation is a key factor here. Lets examine a poker game, one situation where the pot is large and one when it is small. The way we perceive multiple hands is influenced by the prize. If we play the game for the sake of playing well and the prize (extrinsic motivation) has little of no appeal, then we may perceive hands throughout the game, according to this article, would be different than if a larger prize was present.It seems that intrinsic motivation can be looked at through experiments like this, and that higher level processing may have a larger effect than emotions such as desire.

  9. #9 PlaydoPlato
    January 12, 2010

    There’s a story about the Spanish Explorer, Cardenas, who is credited with discovering the Grand Canyon. While standing on the south rim, and despite the advice of his Indian guides, he grossly underestimated the distance down to, what’s known today, as the Colorado river.

    Days later, the hiking party struggled back to the rim, exhausted and severely dehydrated after having failed to reach the river.

    The conventional explanation for their failure is that, in those days, the air at the canyon was so crystal clear that the usual atmospheric haze that we use to help us gauge distances was absent, thus making the river seem closer than it really was.

    This perception study suggests another reason. As explorers, the river was a highly desirable target to Cardenas’ men, and as their water ran out and their thirst grew, it became even more desirable.

    I wonder if this glitch in our distance perception occurs on a figurative level as well. Do we perceive our chances as better, as in closer, with scoring a hot date or winning the lottery because both of those outcomes are highly desirable?

    The flip side of this is: Do we perceive lung cancer, heart disease, etc. as less likely, as in farther away, because they are undesirable outcomes?

  10. #10 Ken Granderson
    January 15, 2010

    Cardenas ‘discovered’ the Grand Canyon only in the minds of the Europeans.

    It was common knowledge to the people who had been living there for thousands of years.

  11. #11 tresho
    February 7, 2010

    It was common knowledge to the people who had been living there for thousands of years. You seem to have an uncommon definition of the word ‘common’. In Cardenas’ time, only the local inhabitants and a very few others knew about the Grand Canyon. When the news of the canyon spread to people thousands of miles away, then that knowledge started to become ‘common.’ Until Columbus’ ‘discovery’ the existence of the other hemisphere of the earth and its land masses was not ‘common’ by any reasonable definition of the term. Very few people living in the western hemisphere knew about the eastern hemisphere & vice-versa. Whether Columbus personally realized he had found something other than India is not material to his making a ‘discovery.’ The doomed Viking colony in Greenland, although known to a few in Europe prior to Columbus, was a discovery that led nowhere.
    The conventional explanation for their failure… To this very day, many Grand Canyon hikers repeat Cardenas’ mistake and try to hike without sufficient water or other precautions. Endangered hikers have even been known to refuse advice & assistance offered by rangers on the spot. Sometimes they die from their mistakes. This happens despite numerous signs at the trailheads and along the canyon rim, which if heeded, would prevent many injuries and deaths. Any theory about how Cardenas got into trouble must be reconciled with more recent, and very similar, events that recur in Grand Canyon National Park.

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