Lecture Notes on Mental Imagery and Attention

outline - Mental imagery - Visual vs verbal imagery - Mental representations of visual environments - Attention - Definition of attention - Theories of attention - Early-selection theories - Late-selection theories - Types of attention - Voluntary vs reflexive attention...

outline - Mental imagery - Visual vs verbal imagery - Mental representations of visual environments - Attention - Definition of attention - Theories of attention - Early-selection theories - Late-selection theories - Types of attention - Voluntary vs reflexive attention - Attention and behaviour - Features integration - Dual task performance Representation of information - For the mind to process information, it has to be represented in a way the mind/brain can manipulate it - How is information represented in the mind? - Analogy: e.g., colour representation in a computer (RGB colour model) Visual vs verbal imagery - Mental representations of visual and verbal information - Processing of visual (or visuospatial) and verbal information exhibits different properties  Representations of visual information - Change blindness---inability to notice (salient) changes in a visual scene - We might feel that our visual perception captures all the rich details of the environment, but apparently it doesn't - On the one hand, we have a great ability to recognise visual scenes - e.g., Standing (1973): after studying 10000 pictures, participants accurately recognised 8300 of them! - On the other hand... - Boundary extension - When we memorise a visual scene, a wider-angle view of the scene tends to be stored in memory - Correct rejection rate - When the changed object did not affect the meaning of a scene: 60% - When the changed object altered the meaning of a scene: 94% - What do Standing (1973), Intraub and Richardson (1989), and Mandler and Ritchey (1977) studies tell us about the nature of mental visual representations? - When we perceive a visual scene, two types of representations seem to be formed - Representation of the meaning of the scene - Representation of surface properties of the scene (visual details, colour, etc.) - The meaning (or the gist) of the scene is very well represented - The surface properties are not What is attention - Everyone knows what attention is. It is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought. Focalization, concentration of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others, and is a condition which has a real opposite in the confused, dazed, scatterbrain state. -- From "Principles of Psychology" by William James (published in 1890) - We often receive more information than we can process simultaneously - In order to use our neural and cognitive resources effectively, it is necessary to select important pieces of information for further processing - This selection mechanism is called "attention" When does attentional selection occur - There should be a point in the path from sensation to action at which people cannot process all the information in parallel (attentional "bottleneck") Early and late-selection theories - Different theories about when selection occurs - Vary depending on how early or late they think the bottleneck is Early-selection theory 1: the filter theory - Sensory information has to pass through some bottleneck - Only some of the sensory information is selected for further processing - Dichotic listening task - The unattended message is usually not remembered - Consistent with the filter theory - However, some information about the unattended message is processed - Some non-semantic aspects of the message (e.g., whether the voice was male or female) are remembered later - This does not support the filter theory - Cocktail party effect - You can hear your name mentioned in a crowded bar, even when you are talking with someone else - Some semantic information can also pass through a bottleneck without attention Early-selection theory 2: the attenuation theory - Salience of unattended stimuli is reduced, but they are not filtered out entirely  Late-selection theories - The filter occurs after the perceptual stimulus has undergone analysis for its semantic content fig\_3.05.jpg 00056FCDPM4\_061 BBE9038F: Early vs late-selection - Treisman and Geffen's (1967) dichotic listening task - Participants had to shadow one message from one ear - At the same time, they had to detect a target word, which was heard by either ear - Predictions - The attenuation theory: the target will be less frequently detected in an unshadowed ear - Late-selection theories: the target will be detected equally well in either ear - Results (detection accuracy) - In the shadowed ear: 87% - In the unshadowed ear: 8% - Supports the attenuation theory Voluntary vs reflexive attention - Voluntary attention - Top-down, goal-directed - Reflexive attention - Bottom-up, stimulus-driven Voluntary attention - Focus of attention is usually the same as the focus of the eyes - But not always - Posner's cueing paradigm fig\_3.06.jpg 00056FCDPM4\_061 BBE9038F: Reflexive attention - Similar processing enhancement is observed when reflexive cues are used - But only when the target appears soon after the flash (approximately within 50--200 ms  - When more time passes between a reflexive cue and a target, response to the target can get *slower* - The reflexive attention system has built-in mechanisms to prevent reflexively directed attention from being stuck at a location for too long (*inhibition of return*) Featured integration theory - People must focus attention on a stimulus before they can synthesise its features into a pattern - In essence, attention works as glue with which various features are combined into an object fig\_3.12.jpg 00056FCDPM4\_061 BBE9038F: Feature integration theory - Illusory conjunctions of features (e.g., **T**) occur almost as frequently as correct combinations (e.g., **T**) - Without focussed attention, individual features are perceived but they are not always combined properly Dual-task performance - Can we do two (or more) things simultaneously without having any interference? - The answer to this question depends on the degree to which tasks involved require attention Stroop effect