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Attention Chapter 4 1  What is 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 other excluded Limited in capacity Attention can be dire...

Attention Chapter 4 1  What is 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 other excluded Limited in capacity Attention can be directed: 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? Because our senses provide more information than our brains are able to process. Because our working memory can only hold and process a limited amount of information at once Selective Attention  Early Attention Research 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 Participant “shadows” one message to ensure he/she is attending to that message. In the shadowing procedure, a person repeats out loud words as they are presented.  Dichotic Listening (Cherry, 1953) Major questions: 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 could accurately shadow the message attention system could filter out the other message After completing the task, participants could not report the contents of the unattended message Knew that 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 e.g., Broadbent’s early selection Filter model Late in processing? after the meaning of the messages have been processed e.g. McKay (1973) late selection model In between? e.g., Tresiman’s intermediate selection Attenuation model  Broadbent’s Filter Model Select information based on physical characteristics of the stimuli ear, pitch, spatial location, etc. Unattended information is filtered out before it can be sent to brain areas responsible for analyzing the meaning of the message  Broadbent’s Filter Model Filter: Identifies messages based on physical characteristics A “bottleneck” that limits information transfer Only attended message is passed on Detector: Processes information to determine meaning Information sent to memory and consciousness Broadbent’s Model Could Not Explain Participant’s can sometimes detect highly salient information in the unattended message e.g., their own name  Tresiman’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 the Dictionary Unit of 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 Dear Aunt Jane (Gray & Weddeburn, 1960) 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 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 “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”  McKay (1973) After shadowing the participants were given a memory test Participants had to choose which option was closest to the meaning of attended to message: They threw stones toward the side of the river yesterday They threw stones at the savings and loan yesterday  McKay (1973) 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 On the basis of this result McKay proposed that: 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 Thus, explaining why some evidence indicates early selection and other evidence indicates late selection But, what determines when selection is early or late? Cognitive Resources and Cognitive Load Cognitive Resources & Task Load Cognitive Resources: processing capacity that can be allocated to perform cognitive tasks Task Load (Cognitive Load): Amount of cognitive resources are used to accomplish a task High-load tasks: uses almost all; no resources for other tasks Low-load tasks: uses few; 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) A or B: Press Right Button C or D: Press Left Button 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? X is the target, N is the flanker (a) Low load, easy to find target (b) High load, difficult to find target (c) flankers did not affect RT in the high load condition Task Load and Compatibility Effects No Flanker distraction effect in the high-load condition Participants resources allocated to processing target No resources to process the distractor Evidence that selection occurred before the distractor was identified (early selection) Similar evidence is presented in your textbook Cartoon dog distractor only affects performance in easy task Cognitive Resources & Task Load Similar to earlier experiments, peripheral distractors can show evidence of either early or late selection The locus (high/low) of selection is affected by Task Load The principle that the human mind has limited cognitive resources provides a possible explanation for inconsistent results obtain by previous attention selection experiments (e.g., dichotic listening) The locus of selection is dependent on the amount of cognitive resources available Overt Attention & Covert Attention Orienting  Overt and Covert Attention The are many mechanisms that aid in focusing attention on a stimulus Some of these mechanisms are overt Body movements to align our sense organs to better detect the stimulus Other mechanisms are covert Internal processes e.g., changes in neural responses to the stimulus  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 Depends on characteristics of the stimulus Colour, luminance, & motion difference are highly salient  Top-Down Determinants of Eye Movements Our goals and knowledge are also used to direct attention (endogenous attention): Top-down process Our knowledge obtain from previous experience 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 presentation of the target If the cue predicts the target location most of the time (e.g. 80%) 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 (a) valid trials and (b) invalid trials in Posner et al.’s (1978) precueing experiment; (c) the results of the experiment.  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  Divided Attention Frequently there are multiple important source 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 Contained distractors characters On half of trials 1 of the frames contained a target from the memory set Task: determine if a target was presented  Easier Consistent mapping condition. Targets and distractors were always from different categories e.g., if targets were numbers, distractors were letters Improvement in performance with practice in Schneider and Schiffrin’s (1977) consistent mapping condition. The arrow indicates the point at which participants reported that the task had become automatic.  Consistent Mapping Condition Performance increased with practice Participants became able to efficiently divide their attention across all the items in the test frames With sufficient practice the task became automatic: The task could be accomplished without effort (or even intention) and without consuming appreciable cognitive resources  Automaticity Many tasks become automatic with practice Reading is highly automatic in most people This gives rise to the Stroop Effect: When naming the colour of ink, performance is slowed if the ink is used to write the name of another colour Automatically reading the word interferes with the person's intention of naming the ink colour Stroop Effect  Varied Mapping Condition Schneider & Shiffrin also used a more difficult Varied Mapping Condition: Target and distractors are from the same category A target on one trial can be a distractor on a later trial This task required Controlled Processing: Subject had to pay close attention to the test frames Consumed a lot of cognitive resources Search was slow and effortful – you really have to try Even with lots of practice, participants never achieved automatic processing  Divided Attention: Summary Divided attention is possible Can become automatic: for types of tasks that do not interfere with with other if tasks are easy if well-practiced Is difficult or impossible when tasks are hard Can consume 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  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 visual discriminations Attention speeds visual processing React to changes faster Attention affects if we notice something at all Video: The Amazing Colour Changing Card Trick (2 min 43 sec)  Inattentional blindness: Inattentional blindness: a stimulus that is not attended is not perceived, even though a person might be looking directly at it Video: Gorilla on the Court (3:10)  Change Blindness Change blindness: if shown two versions of a picture, differences between them are not immediately apparent Identifying differences requires concentrated attention and search Video: Piecing things Together (4:00) Feature Integration Theory (FIT)  Feature Integration Theory (FIT) FIT proposes that attention is necessary to integrate the separately analyzed features into coherent objects (Binding) Steps in Treisman’s feature integration theory. Objects are analyzed into their features in the preattentive stage, and then the features are combined later with the aid of attention.  Feature Integration Theory (FIT) Preattentive stage: Automatic No effort or attention Unaware of process Object analyzed into features Corresponds to feature detection cells in visual cortex Focused attention stage: Features are combined if attention is directed to the location of the objects  Treisman and Schmidt (1982) Examine visual perception of unattended objects Used a dual-task: Presented a pair of numbers and a set of differently coloured shapes Very brief display duration (200 ms) Followed by a random dot mask to overwrite sensory memory Primary task: report the numbers (requires attention) Secondary task: report the shapes  Treisman and Schmidt (1982) Participants report illusionary conjunctions: objects that combine features from different stimuli. e.g., a red triangle & a yellow circle is reported as yellow triangle & red circle Occurs because features are “free floating” if not attended Why don’t we notice illusionary conjunctions all the time? Often don’t notice unattended objects at all Can use top down processing to correctly join features of objects that you are familiar with FIT: Neuropsychological Evidence Patient with Balint’s syndrome (R.M.) Inability to focus attention on individual objects High number of illusory conjunctions reported Unable to perform conjunction searches: Searches for targets that are defined by having combination (conjunction of features) e.g. find a green horizontal line  Attentional Networks Ventral Attention Network: Controls attention based on bottom-up salience (exogenous) Dorsal Attention Network: Controls attention based on top-down information (enogenous) Executive Attention Network: Controls other attention networks Directs attention to information needed for current goals Deals with conflicts between systems, information, habits and goals