IBP: Introduction to cognitive psychology

Chapter 2:  Perception

Perception: The subjective experience of sensory information after having been subjected to cognitive processing

1. Visual perception

Theories of visual perception:

• Template theory: a system which uses information from past experience to make sense of a new stimulus
  • Template: Stored representations of objects enabling object recognition
• Gestalt theory (1): if we are to recognise objects, we need to be able to tell them apart from everything else
  • Reversible figure: a figure in which the object perceived depends on what is designated as‘figure’ and what is designated as ‘(back)ground’.
• Gestalt theory (2): laws are needed to group parts of a visual scene into objects:
  • Laws of perceptual organisation:  Principles (such as proximity) by which parts of a visual scene can be resolved into different objects
• Feature extraction theories: break objects down into their component features
  • Features: elements of a scene that can be extracted and then used to build up a perception of the scene as a whole
  • Selfridge's pandemonium: a conceptual model of a feature extraction process.​​​​​
• Marr's computational theory: approach that concentrated on the implementation of some of the processes discussed above, progressing through a number of stages until an internal representation of the viewed object is achieved
  • Primal sketch: First stage in Marr’s model of vision, which results in computation of edges and other details from retinal images
  • 2.5-D sketch: Second stage. Aligns details in primal sketch into a viewer-centred representation of the object
  • 3-D sketch: Third stage. This is a viewer-independent representation of the object which has achieved perceptual constancy or classifcation
• ​​​​​​​​​​​​​​Biederman's recognition-by-components approach:based on feature extraction, however, the features are three-dimensional and are referred to as geons
• Paralell distributed processing approaches: Stimuli are represented in the brain, not by single neurons, but by networks of neurons. An approach sometimes used to model cognitive processes
• Constructivist approach: Building up our perception of the world from incomplete sensory input
  • ​​​​​​​Perceptual hypotheses: An element of the constructivist approach, in which hypotheses as to the nature of a stimulus object are tested against incoming sensory information.
• ​​​​​​​The Gibsonian view of perception: perception should be considered in terms of how it allows us to interact with the world we live in
  • ​​​​​​​Direct perception: The basis of direct perception is that the sensory information available in the environment is so rich that it provides suffcient information to allow a person to move around, and interact with, the environment without the need for any top-down processing.

Illusions: Cases in which perception of the world is distorted in some way

• ​​​​​​​Bottom-up and/or top-down processes generate illusions
• ​​​​​​​Size constancy: the perceived size of objects is adjusted to allow for perceived distance.
• Numena: the world as it really is
• Phenomena: the world as we perceive it
• Phenomenological experience: our conscious experience of the world.
• Sensory conspicuity: The extent to which aspects of a stimulus (such as colour and luminance) infuence how easily it canbe registered by the senses
• Attention conspicuity: The interaction of aspects of a stimulus(such as colour, luminance, form) with aspects of an individual (such as attention, knowledge, pre-conceptions) that determine how likely a stimulus is to be consciously perceived.
• Visual search: Experimental procedure of searching through a feld of objects (`distractors’) for a desired object (`target’)
• Visual masking: Experimental procedure of following a briefy presented stimulus by random visual noise or fragments of other stimuli. Interferes with or interrupts visual processing
  • the mask is effective because it disrupts re-entrant processing (Information fow between brain regions(bidirectional).
     

Sensation vs perception: Sensation will be considered to be the ‘raw’ bottom-up input from the senses and perception will be considered to be the end result of the processing of that sensory material within the visual system

Structure of the visual system: 

• Ventral stream: A pathway in the brain that deals with the visual information for what objects are
• Dorsal stream: A pathway which carries visual information about the spatial location of an object

2. Auditory perception

Auditory localisation: usually described using the following three coordinate systems:

• Azimuth (horizontal):  determined primarily by binaural cues, specifcally time and intensity differences between stimuli reaching the left and right ears
  • Binaural cues: cues that rely on comparing the input to both ears, as for example in judging sound direction
• Elevation (vertical): determined mainly by spectral cues which are generated by the way in which the head and outer ears (pinnae) affect the frequencies in the stimulus
  • Spectral cues: auditory cues to, for example, distance provided by the distortion of the incoming stimulus by (e.g.) the pinnae (ear lobes)
• Distance coordinate: how far a sound source is from the listener
  • There are several mechanisms for auditory far-distance judgement, which are used together to determine perception of a sound’s distance, they include:
    • Sound level
    • Frequency
    • Motion parallax
    • Refection

Auditory attention: These are the ways we can help to direct our auditory attention:

• Location: Sounds created by a particular source usually come from one position in space or move in a slowly changing and/or continuous way (e.g. a passing car).
• Similarity of timbre: Sounds that have the same timbre are often produced by the same source, i.e. similar sounding stimuli are grouped together.
• Sounds with similar frequencies are often from the same source.
• Temporal proximity: Sounds that occur in rapid progression tend to be produced by the same source

Phantom word illusion:What we hear may be infuenced by what we expect to hear

Mental model: a representation that we construct according to what is described in the premises of a reasoning problem, which will depend on how we interpret these premises.

Sensory overload: A situation in which there is too much incoming sensory information to be adequately processed.

3. Haptic perception

Haptic perception: Tactile (touch) and kinaesthetic (awareness of position and movement of joints and muscles) perception

Haptic information: what we produce when combining our sense of touch and kinesthesis

• the way we obtain haptic information has a lot in common with active perception: perception as a function of interaction with the world​​​​​​​

Resources:

An Introduction to Cognitive Psychology: Processes and Disorders 3rd edition (Groome, David)