Psychology Chapter on Attention Models

Attention

• Attention: The focusing of mental effort on selected aspects of the environment or mental activities and the blocking out of others.
• Selective: Some things are selected, others excluded.
• Limited in capacity.
• Directed attention:
  • Goal-driven mechanism: attend to what you choose to.
  • Stimulus-driven mechanism: attention is captured by salient events (e.g., loud sounds).

Why do we need attention?

• Our senses provide more information than our brains are able to process.
• Our working memory can only hold and process a limited amount of information at once.

Selective Attention

• Early attention research and theory focused on auditory attention.
• Specifically the "cocktail party problem".
• People's ability to listen to one message while ignoring other messages.
• Dichotic Listening Task:
  • One message is presented to the left ear and another to the right ear.
  • The participant "shadows" one message to ensure they are attending to that message.
  • In the shadowing procedure, a person repeats out loud words as they are presented.
• Dichotic Listening (Cherry, 1953):
  • How effectively can we select a message?
  • Does the unattended message interfere?
  • How much processing does the unattended message receive?
  • What can we use or remember from the unattended message?

Early Dichotic Listening Experiments

• Participants were able to accurately shadow the message.
• The attention system could filter out the other message.
• After completing the task, participants could not report the contents of the unattended message.
• Knew there was a message.
• Noticed basic physical characteristics of the message (volume, pitch).
• Knew the gender of the speaker (related to pitch).
• Unaware of even frequently repeated information.

Results of Early Dichotic Listening Experiments

• However, the unattended ear is being processed at some level.
• Changes in basic sensory features in the unattended ear are noticed:
  • Change in gender midway through task is noticed.
  • Change from a voice to a tone is noticed.

Explaining Dichotic Listening

• Clearly, people can effectively select one message and reject another.
• But, at what point in processing does selection occur?
  • Early in processing? (e.g., listen to the left ear not the right, Broadbent's early selection Filter model)
  • Late in processing? (e.g., after the meaning of the messages have been processed, McKay (1973) late selection model)
  • In between? (e.g., Treisman's intermediate selection Attenuation model)

Broadbent's Filter Model

• Select information based on physical characteristics (e.g., ear, pitch, spatial location).
• Unattended information is filtered out before it can be sent to brain areas responsible for analyzing the meaning of the message.
• Filter: identifies messages based on physical characteristics and limits information transfer. Only the attended message is passed on
• Detector: Processes information. Information is sent to memory and consciousness.

Broadbent's Model Could Not Explain

• Participants can sometimes detect highly salient information in the unattended message (e.g., their own name).

Treisman's Attenuation Theory

• Replaces filter with an attenuator.
• Analyzes incoming message.
• Analysis proceeds only far enough to separate messages.
• Attended message is passed on at full strength.
• Unattended message is passed on at a reduced strength.

Example thresholds for Treisman's model

• A person's name has a low threshold, so can be easily detected.
• The thresholds for the words rutabaga and boat are higher, because they are used less or are less important.
• Unattended messages that have been attenuated can still be detected if the detection threshold is low.

Evidence for Late Selection

• Participants will sometimes shadow meaningful messages that switch from one ear to another rather than following directions to shadow one ear.
• Must have some awareness of the meaning of the unattended message.

Late Selection Models

• Selection of stimuli for final processing does not occur until after information has been fully analyzed for meaning.

McKay (1973)

• Dichotic listening experiment.
• In attending ear, participants heard ambiguous sentences (e.g., "They were throwing stones at the bank.").
• In unattended ear, participants heard words related to different meanings of the ambiguous words (e.g., "river" or "money").
• After shadowing the participants were given a memory test
• Participants had to choose which option was closest to the meaning of attended to message.
• The meaning of the biasing word affected participants' choice. (e.g., if unattended word was 'money'; selected: "They threw stones at the savings and loan yesterday").
• Participants were unaware of the presentation of the biasing words.
• Attention only suppresses the unattended message after the meaning of both message have been fully analyzed (late selection).

Early vs. Late

• There has been a great deal of debate regarding the level of processing at which selection occurs (early vs. late).
• Current thinking is that both early and late selection are possible.
• Different types of attentional filters are used in different circumstances, explaining why some evidence indicates early selection.

Cognitive Resources & Task Load

• Cognitive Resources: processing capacity.
• Task Load (Cognitive Load): Amount of cognitive resources.
• High-load tasks: uses almost all cognitive resources, no resources for other tasks.
• Low-load tasks: uses few cognitive resources, resources available for other tasks.

Flanker-Compatibility (Eriksen's Flanker) Task

• Participants must identify a target item by pressing a button.
• The target is flanked by 'distractors'.
• The distractor may be associated with:
  • The same response button as the target (compatible).
  • A different response button (incompatible).

Task Load and Compatibility Effects

• When task load is low:
  • Reaction time is longer for incompatible distractors.
  • Indicates late selection.
  • Participant still had resources available to process the unimportant distractors.
  • If task load is increased will there still be a distractor effect?

Over and Covert Attention

• Many mechanisms aid in focusing attention on a stimulus.
• Some mechanisms are overt (e.g., body movements to align our sense organs).
• Other mechanisms are covert (e.g., internal processes, changes in neural response).

Visual Overt Orienting

• Body, head & eye movements that position the image of the attended stimulus on the appropriate region of the retina
• Usually the fovea because it has the highest acuity.
• We foveate stimuli by making rapid eye movements called saccades.
• The pauses between eye movements are called fixations.

Bottom-up Determinants of Eye Movement

• Some stimuli capture attention (exogenous attention).
• Stimuli that are easily noticed are said to be salient.
• Bottom-up process that depends on characteristics of the stimulus (e.g., colour, luminance, & motion).

Top-Down Determinants of Eye Movements

• Our goals and knowledge are used to direct attention (endogenous attention).
• Top-down process where our knowledge from past experiences affects how we direct our attention
• Object salience can be affected by current goals.

Visual Covert Orienting

• Shifting attention to regions of the visual field without overt movements of the body or eyes.
• Covert attention can both enhance the processing of attended stimuli and inhibit the processing of unattended stimuli.
• The "spotlight of attention" refers to a region of the visual field that is selected for enhanced processing.
• The locus of covert attention must be inferred from measures of stimulus processing (e.g., reaction time, accuracy, measures of brain activity

Cue-Target (Precueing) Paradigm

• Precueing: Information (a cue) that directs attention to a spatial location before the target is presented.
• If a cue predicts the target location most of the time, it is called a predictive cue
• When the cue is predictive, participants respond faster to a target at the cued location (valid trial) than at an uncued location (invalid trial)
• Even when eye movements are not permitted.

Physiology of Attention

• Converging evidence from many techniques (single cell recording, EEG, neuroimaging, neuropsychology) has shown that attention:
  • Involves processing that is distributed across a large number of areas in the brain.
  • Enhances neural responding to attended stimuli.
  • Can suppress responses to unattended stimuli.

Divided Attention

• Frequently, there are multiple important sources of information that we want to attend to.
• We can effectively divide our attention under some circumstances but there are limitations.
• Divided Attention: Schneider & Shiffrin (1977): Divide attention between remembering target and monitoring rapidly presented stimuli, Memory set: 1-4 target characters, Test frames: 20 images presented in rapid succession
  • Consistent mapping condition: When targets and distractors are from different categories.
  • Varied mapping condition: When targets and distractors are from the same category, consuming a lot of cognitive resources.
• Divided attention is possible, can become automatic (e.g., tasks not interfering with others, easy tasks) but is difficult or impossible when tasks are hard; it can consume up to a great deal of cognitive resources

Strayer and Johnston (2001)

• Simulated driving task.
• Participants on cell phone missed twice as many red lights and took longer to apply the brakes.
• Same result using "hands-free" cell phone

Attention and Visual Perception

• Much of modern attention research focuses on how attention affects visual perception.
• Attention can improve the quality of perception (e.g., better able to make fine discriminations).
• Attention speeds visual processing, enabling reaction to changes faster.
• Attention affects if we notice something at all. (Inattentional blindness). Change blindness

Inattentional blindness

• A stimulus not attended to is not perceived, even if a person is looking directly at it.
• Video: Gorilla on the Court (3:10)
• Change blindness: If shown two versions of a picture, differences are not immediately apparent. (Video: Piecing things Together (4:00)).

Feature Integration Theory (FIT)

• Attention is needed to integrate separately analyzed features into coherent objects.
• Pre-attentive stage: features are automatically analyzed.
• Focused attention stage: attention directs combination of features.

Treisman and Schmidt (1982)

• Examined visual perception of unattended objects using a dual-task (numbers and shapes).
• Participants reported illusionary conjunctions (e.g., red triangle as yellow triangle, red circle).
• Illusionary conjunctions occur because features are “free-floating.”

FIT: Neurological Evidence

• Patient with Balint's syndrome: High number of illusory conjunctions, inability to focus attention on individual objects, and inability to perform conjunction searches (searches for targets defined by combinations of features).

Attentional Networks

• Ventral Attention Network: Bottom-up salience (exogenous).
• Dorsal Attention Network: Top-down information (endogenous).
• Executive Attention Network: Controls other attention networks; deals with conflicts between systems.

Automaticity

• Many tasks become automatic with practice, like reading; this gives rise to the Stroop Effect (when naming the color of ink is slowed, if ink is used to write the name of another color).