Perceptual Distortion

Many psychiatric disorders are characterised by perceptual abnormalities, ranging from sensory distortions to illusions and hallucinations. The distinction.
Table of contents

The Necker Cube illusion is a bistable visual illusion. The same sensory data are able to support two perceptual inferences one in which corner 1 is closest to the observer, the other in which corner 2 is closest. If sensory data alone cannot support perception, how does the brain create accurate perceptual representations of the world? It is now appreciated that ill-posed problems such as vision can be made tractable by using contextual information to impose constraints on the interpretation of ambiguous data. In the case of vision, for example, past experiences of seeing similar visual scenes sets up expectations about the likely current state of the world, and any new sensory data are interpreted in light of these expectations.

The ability of the brain to make sense of sensory information has inspired computer scientists working on computer vision and similar problems to take a similar approach. These networks are particularly good at detecting features and patterns in new data, and using these features to perform classification tasks. This is similar to what the brain does when engaged in perceptual inference, which may be thought of as the detection of objects and meaningful patterns in sensory data. At each layer the network attempts to extract patterns and features from these data, with higher layers of the network extracting increasingly more abstract features.

Perceptual distortion | Psychology Wiki | FANDOM powered by Wikia

During training the network is exposed to many different data-sets e. The network is able to self-calibrate, guided by its successes and errors, in a process analogous to synaptic plasticity. After exposure to thousands of images of, say, cats, the network learns to recognise cats in images to which it has never before been exposed.

Perceptual distortions

The well-trained ANN is primed to recognise salient features and patterns in new data in much the same way that the brain is primed to recognise the patterns in sensory data that are most important for detecting behaviourally relevant objects. Prior to training, the ANN is essentially blind to meaningful patterns in new data.

In both the well-trained ANN and the mature human visual system the final decision about what a new image represents is the product of a delicate balance between the information contained within the image itself and the readiness of the network to detect certain features within new data. Perception is therefore the product of two sources of information: What happens, however, when prior expectations are given too much weight?

The Google researchers provide an intuitive example of the problems that inappropriately strong prior expectations can cause in their ANN.


  • Perceptual distortions and deceptions: what computers can teach us.
  • Perceptual distortions and deceptions: what computers can teach us!
  • The Work of Washington Irving?
  • Perceptual Distortion in Deadly Situations - Body Worn Video Steering Group.

This manipulation inappropriately weighted prior expectation relative to sensory data. Although the mechanisms employed by this simple network manipulation are not intended to be biologically plausible, the simple experiment demonstrates the power that inappropriately held prior expectations might have on resulting perception. To what extent can inappropriately held prior expectations influence human perception? This question has relevance to descriptive psychopathology and psychiatry. We have argued that perceptual inference always relies on both incoming sensory data and a prior expectation about what these data are likely to represent.

Additionally, we have outlined the hypothesis that illusions and hallucinations may be the result of an imbalance between these two sources of information. This simple account is consistent with contemporary theories of illusions and hallucinations, which also implicate a miscalibration between these two sources of evidence.

Perceptual distortion

One of the most influential contemporary accounts of perceptual inference is that of hierarchical predictive coding. Incoming sensory data are compared against this representation. If there is a good match between the prior prediction and the sensory data the current representation of the state of the world is reinforced. The iterative process of matching the brain's predictions to sensory signals underlies perceptual inference. The brain's internal representation of the world will be resistant to change, and thus dominate perceptual inference, if the prior prediction is given a greater weight than the incoming sensory data, as may happen when the incoming sensory data are noisy.

Another influential account of complex visual hallucinations is the perception and attention deficit PAD model, which was developed after studying clinical populations who experience recurrent complex visual hallucinations. In people who have a combined deficit in sensory processing and attention it is conceivable that proto-objects from a misrepresentative pool become inappropriately bound to the visual scene, resulting in a hallucination.

Both the predictive coding and PAD accounts of illusions and hallucinations propose that an overweighting of prior expectation relative to sensory data may underlie certain perceptual abnormalities. This overweighting may be a direct result of inappropriately held prior expectations as can occur in states of high emotional arousal , or may be secondary to a decrease in the quality or precision of incoming sensory data as may occur in states of low attention, fatigue or sensory impairment. First, although Google's ANN provides a nice visual example of the power of overweighted prior expectation, it has key structural and functional differences when compared with the human visual system.

Among these are the fact that Google's network hierarchy has many more layers than our current best estimates in the primate brain. Perhaps more importantly, expectation-based accounts of illusions and hallucinations fall short of explaining some of the most frequently encountered perceptual abnormalities in clinical practice. The hallucinations recounted by patients with psychosis or organic disorders are often bizarre, and seem entirely unexpected given the environmental context. Although psychiatrists ask patients about perceptual abnormalities on a daily basis, it is not often that we stop to ponder what actually distinguishes normal perceptions from perceptual distortions and deceptions.

Current work in psychology, neuroscience and computer science paints a picture of normal perception as being inextricably linked to prior expectations about the state of the world. Perception depends on a delicate balance between the sensory information that we are confronted with, and the prior expectations we have about the world. If the balance is disturbed then perceptual inference becomes disrupted.

Expert Answer

Without prior expectations, perception is a mathematically ill-posed problem 4 , 9 as illustrated by Fig. As a result, the division between veridical perception and perceptual distortions or deceptions is more subtle than one of clear qualitative difference. Declaration of interest None. National Center for Biotechnology Information , U.

Nour 1, 2 and Joseph M. Correspondence to Matthew M. This is an open-access article published by the Royal College of Psychiatrists and distributed under the terms of the Creative Commons Attribution License http: This article has been cited by other articles in PMC. Abstract The nature of perception has fascinated philosophers for centuries, and has more recently been the focus of research in psychology and neuroscience.

The problem of perception How does your visual system construct a representation of the world?

The problem of perception

Open in a separate window. Expectation is necessary for perception If sensory data alone cannot support perception, how does the brain create accurate perceptual representations of the world?


  • OLYMPIC WANDERING: Time Travel Through Greece?
  • Because He Could.
  • ;
  • .
  • Experience of Perceptual Distortion as a Source of Anxiety!
  • Expressway.

Tipping the balance Perception is therefore the product of two sources of information: Contemporary accounts of hallucinations We have argued that perceptual inference always relies on both incoming sensory data and a prior expectation about what these data are likely to represent. Conclusions Although psychiatrists ask patients about perceptual abnormalities on a daily basis, it is not often that we stop to ponder what actually distinguishes normal perceptions from perceptual distortions and deceptions. Footnotes Declaration of interest None.

This occurs when one forms an opinion of others on the basis of first impressions. We are often told that in an interview first impressions count because what we do an say can have an impact on how the interviewer perceives us and whether we get the job or not. During recruitment, an interviewer is expected to observe and evaluate a number of prospective candidates.

His evaluation process can be diluted by the primacy effect because he may start judging the candidates by their first impressions. A candidate who is nervous in the first few minutes of an interview can be judged by the interviewer to be the type who cannot handle pressure. This occurs when individuals are prejudged on baseless and non factual information, beliefs, attitudes and emotions. For example people hold prejudice views towards individuals from a certain race classic example of this is Hitlers hatred toward the Jews.

In order to decrease the errors involved in perception, one has to keep in mind the way the perceptual process works. By understanding the process one can do a better job at minimizing their negative effect.

Perceptual Distortion in Deadly Situations

One can compare one's perception with other people, if they are representing different backgrounds, cultures or training. This may lead to agreements or otherwise, communications can help to sort out the differences. One should make an effort to understand the other person's point of view, it may help to know when one is wrong. The point is that one should listen and understand the other person rather than try to convince him or her that one is right.

Fourthly, one should be willing to change, when one comes across new information. One should gather enough information before jumping to conclusions. It is imperative that this information be factual to avoid any further errors and that the right course of action be administered. Finally, one should view the world in dynamic terms, because one's behaviour can alter the phenomenon that is the basis for one's perceptions, so, one must notice the impact of one's own behaviour.


  • Solved: List The Major Causes Of Perceptual Distortion? Ho | leondumoulin.nl;
  • Les trois villes: Lourdes (French Edition).
  • Middle School: The Worst Years of My Life: (Middle School 1).
  • LADIES BELT. Vintage Crochet Pattern!
  • How My Twin Soul Wife Became a Prostitute (A True Story).

Perceptual errors can lead to lower employee performance, low morale, poor decision making and an overall reduction in the effectiveness of the organization. Comment on this answer. Please provide additional information to the answer.