Psychology: Visual Perception

Visual Perception

Sensation

The physical detection of stimuli using the five senses; sight, hearing, taste, touch, and smell.

Perception

consciousness and interpretation of sensory information, allowing us to make sense of our environment.

What is the role of the occipital lobe?

The occipital lobe receives visual messages form the eyes and turns this into meaningful information that other areas of the brain can use.

Visual Constancies

They allow people to recognize objects and understand what they’re seeing, even if the appearance has changed. There are three types of visual constancies: shape, color, and size.

Shape constancy

The ability to perceive that the shape of an object has remained the same, regardless of its position.

Color Constancy

The ability to perceive that the color of an object has remained the same even in different light conditions or different viewpoints.

Size Constancy

The ability to perceive that the size of an object has remained the same, no matter how far away or close it is to the eyes.

Depth perception

Allows us to locate objects in our visual field.

Depth cues: Relative brightness

Objects that are brighter are perceived as closer/

Depth cues: texture gradient

The further away the object, the less texture detail can be perceived.

Depth cues: Relative size

As objects move further from the eye, they appear smaller.

Depth cues: superimposition

If one object partially blocks another, the first object is seen as being closer.

Depth cues: height in plane

Objects that are further away appear higher up in the field of vision.

What does the word ‘gestalt’ mean?

The word ‘gestalt’ can be roughly translated from German to mean ‘structure’ or ‘shape’.

Gestalt Theory

The gestalt theory suggests that the whole is different (or more) than the sum of its parts.

Gestalt Principles

Laws of perception to describe the way in which the brain organizes the sensory information it receives.

Figure-ground

An object is differentiated from its background or surrounding area. In an image, the ‘figure’ is the part of what we are looking at that we are paying attention to.

Similarity

Our brains group together objects which share some elements.

Proximity

Describes how human brains perceive elements that are close together (proximate) as more related than elements that are further apart.

Closure

Describes how people perceive incomplete objects as a whole.

Continuity

This law states that when visual elements in an image are aligned with one other, we are likely to perceive them as continuous.

Gibson’s direct theory of perception

A bottom-up approach emphasizing the role of nature and the direct nature of perception.

Optic flow

The pattern of visual information that changes as we move through our environment.

Motion parallax

Occurs when objects at different distances from our eyes move at different speeds across our view as we move.

Invariants

Aspects of the environment that remain constant (do not vary), despite changes in perspective.

Affordances

The opportunities we see as we interact with our environments.

Argument for the direct theory of perception

An argument for the direct theory of perception is the named study on the visual cliff (Gibson and Walk), as it suggests that even young children have depth perception and can perceive threats to their survival in their environment.

Argument against the direct theory of perception

An argument against the direct theory of perception is that it oversimplifies how complex human perception is, as it ignores the influence of expectation and culture on perception.

Gregory’s constructivist theory of perception

A top-down approach which focuses on the role of experience and culture in shaping our perceptual experience.

Schemas

Mental structures that people use to organize and store information about their environment.

Inferences

Conclusions or predictions based on prior knowledge.

Perceptual hypotheses

Educated guesses people make when interpreting sensory information.

Perceptual set

Noticing some aspects of sensory information and not others, based on schemas.

How can culture influence perception?

Our cultural background can shape how we interpret sensory information by considering the different aspects of the environment that are more/less important, depending on the traditions and way of life of the people who live there.

How can motivation and emotion influence perception?

Our emotions can influence how we perceive the world around us, and contribute to our perceptual sets, as we may be more likely to perceive the world in ways that align with how we are feeling.

How can expectation influence perception?

Our experiences influence the way in which we attend to and process sensory information, meaning that we are likely to notice something when we expect to see it.

Argument for the constructivist theory of perception

An argument for the constructivist theory of perception is the named study on familiarity and perception (Haber and Levin, experiment 2 only), as it demonstrates the role that past experiences and familiarity play in accurate perception, as objects that were unfamiliar and therefore of unknown size, height estimates were less accurate, which aligns with the view that perception is not just a direct response to sensory input, but relies heavily on prior knowledge and experience.

Argument against the constructivist theory of perception

An argument against the constructivist theory of perception is that it does not explore the role of nature in perception, which is likely to be as important to our visual experience.

Visual Illusions

Fascinating phenomena where our visual perception does not match reality.

Ambiguous figures

When there are two or more visual interpretations we can perceive in a single image. One example is Leeper’s Lady.

Fictions

Illusions in which our minds ‘add‘ features that do not exist to images. One example is the Kanizsa triangle illusion.

Distortions

When we misperceive the size, length or curve of an object from how it is actually presented. One example is the Müller-Lyer illusion.

Impossible figures

2D illusions that are impossible in 3D. One example is the Penrose triangle illusion.

Relative size

When we incorrectly perceive the size of an object in relation to contextual information. One example is the Ebbinghaus illusion.

What else can be used to explain the visual illusions?

Gestalt principles of perception can be used to explain the visual illusions of ambiguous figures and fictions.

Argument for the influence of culture on experience of visual illusions

An argument for the influence of culture on perception comes from the named study on culture and visual illusions (Bremner et al., experiment 2 only) which found that people from different cultures have different experiences of visual illusions.

Argument against the influence of culture on experience of visual illusions

An argument against the influence of culture on experience of visual illusions is that there are many universal aspects of visual perception which cannot be explained by culture and expectation alone.