Summary: Study provides an answer to the age-old philosophical question of whether people can see the world objectively. In terms of visual perception, the answer is no.
Source: Johns Hopkins University
Johns Hopkins University researchers who study the mind have used methods from cognitive science to test a long-standing philosophical question: Can people see the world objectively?
Their answer, as published in Proceedings of the National Academy of Sciences, is a flat no.
With a novel series of experiments using sophisticated computer graphics and laser-cut “coins,” the Johns Hopkins team found that it’s almost impossible for people to separate an object’s true identity from their own perspective on it. In this case, people looked at round objects that were tilted away from them; even when people were certain that the objects were round, they couldn’t help but “see” them in a distorted way, as ovals or ellipses.
“This question about the influence of one’s own perspective on perception is one philosophers have been discussing for centuries,” said senior author Chaz Firestone, an assistant professor of Psychological and Brain Sciences and director of the Hopkins Perception & Mind Laboratory. “It was really exciting for us to take an experimental approach to this question.”
When humans see things, the brain identifies them by combining raw visual information with ingrained assumptions and knowledge about the world. For example, if you take a circular coin and tilt it away from you, light from the coin hits your eyes in the shape of an oval or ellipse; but your brain then goes beyond that information and makes you “see” a circle in the real world. Philosophers, notably including John Locke and David Hume, have long wondered if it’s possible to separate the way the object really is from how it lands on our eyes—in other words, whether pure objective vision is even possible.
To get at the question, the team designed a “philosophy experiment” for the lab.
Over the course of nine experiments, subjects were shown pairs of three-dimensional coins. One was always a true oval, the other was a circle. Subjects had to pick the true oval. Seems easy, yet when presented with tilted circular coins, subjects were flummoxed and their response time slowed significantly. This persisted whether the coins were still or moving; with different shapes; and whether the coins were shown on a computer screen or displayed right in front of subjects.
Objects are stamped with our perspective, concluded lead author Jorge Morales, a post-doctoral fellow.
“Our subjective approach to the world stays with us,” Morales said. “Even when we try to perceive the world the way it really is, we can’t completely discard our perspective.”
This is the first of several experiments the team is working on using approaches from psychology and neuroscience to test ideas from philosophy. In collaboration with philosopher Austin Baker, they are looking at how stereotypes affect perception—specifically if subjects have a harder time seeing people who defy their gender stereotypes. Another project examines how people perceive objects that aren’t there, or how people notice the absence of things.
“This is a project that really surprised us—we expected ‘objectivity’ to totally overwhelm any influence of the subject’s perspective,” said Firestone. “This is a nice example of how ideas from philosophy can influence the science of the mind and brain.”
Arguably the most foundational principle in perception research is that our experience of the world goes beyond the retinal image; we perceive the distal environment itself, not the proximal stimulation it causes. Shape may be the paradigm case of such “unconscious inference”: When a coin is rotated in-depth, we infer the circular object it truly is, discarding the perspectival ellipse projected on our eyes. But is this really the fate of such perspectival shapes? Or does a tilted coin retain an elliptical appearance even when we know it’s circular? This question has generated heated debate from Locke and Hume to the present; but whereas extant arguments rely primarily on introspection, this problem is also open to empirical test. If tilted coins bear a representational similarity to elliptical objects, then a circular coin should, when rotated, impair search for a distal ellipse. Here, nine experiments demonstrate that this is so, suggesting that perspectival shapes persist in the mind far longer than traditionally assumed. Subjects saw search arrays of three-dimensional “coins,” and simply had to locate a distally elliptical coin. Surprisingly, rotated circular coins slowed the search for elliptical targets, even when subjects clearly knew the rotated coins were circular. This pattern arose with static and dynamic cues, couldn’t be explained by strategic responding or unfamiliarity, generalized across shape classes, and occurred even with sustained viewing. Finally, these effects extended beyond artificial displays to real-world objects viewed in naturalistic, full-cue conditions. We conclude that objects have a remarkably persistent dual character: their objective shape “out there,” and their perspectival shape “from here.”