1Attention Ifailures to select informationWhat is attention?• How is the word used?•Examples:– something bright caught my attention– I didn’t see you, I was paying attention to the game– I struggled to pay attention to the lecture– I don’t remember even cleaning the table, I must not have been paying attention• Attention refers to many different kinds of mechanismsAttention enhances some information and inhibits other information. The enhancement enables us to select some information for further processingThe inhibition enables us to set some information aside.AttentionAttention and limits on information • We need attention to limit the amount of information that is processed• Why are there limits on the amount of information we can process?– limited sensory systems2David Hockney’s photo collage might be a metaphor for the way we see scenes1 photo = 1 gazeAttention and limits on information • Human information processing is massively parallel, up to a point where we have serial bottlenecks• Bottleneck: a restriction on the amount of information that can be processed at once forcing serial processing• Serial bottlenecks:– limited sensory systems– limited effector systems• movements must be planned sequentially• words can only be spoken sequentiallyInattentional Blindness • After bottleneck, it is the allocation of our attention that determines what is analyzed. • Often, we are unable to process information that is unattended. This can lead to inattentional blindness (aka change blindness)• Lots of demos:– http://viscog.beckman.uiuc.edu/djs_lab/demos.html– http://dualtask.org/Change_Blindness_Demo/ChangeBlindness.htmlAirplane demoDinner demoSome of these demos are from: Simons & Levin, 1997, TINS, 1, 261-267Inattentional Blindness• Why is it hard to notice the change (initially)?• When motion detection is disrupted, it is very difficult to observe changes to unattended image locations • Brain makes reasonable assumption that things do not change unexpectedly (in the absence of motion cues). DVD Demo of basketball players• Task: count the number of times the white team passes the ball to each other• Importantto pay close attention to task(Simons & Chabris, Perception, 1999, 28, 1059 – 1074)3Other demo’sDan Simons (University of Illinois): http://viscog.beckman.uiuc.edu/change/demolinks.shtmlsee also letter task: http://www.dualtask.org/Inattentional Blindness• Shows there are remarkable gaps in our perception • Human’s interpretation of the visual field is much sparser than the subjective experience of “seeing” suggests• Our visual system might be overwhelmed without change blindness -- in a real-world setting with many moving objects, it might make sense to “track” only a few objectsFailures of Selection in TimeWhen new information (even if only a small amount) arrives in a rapid stream, spending time processing it will cause you to miss some other incoming information, resulting in what are called failures of selection in time. Attentional BlinkDemos: http://www.rit.edu/~gssp400/Blink/blinkinstr.htmlhttp://www.cs.kent.ac.uk/people/rpg/pc52/AB_Webscript/instr.htmlhttp://psych.hanover.edu/JavaTest/Cognition/Cognition/attentionalblink_instructions.htmlSources of LimitationThe attentional blink is a short period during which incoming information is not registered, similar in effect to the physical blanking out of visual information during the blink of an eye. Divided-attention studies demonstrate that performance is hampered when you have to attend to two separate sources of visual information or two separate visual events. In all these cases, the decrement in performance is referred to as dual-task interference.Disorders of Visual Attention4Hemispatial Neglect• Cause– often a stroke that has interrupted the flow of blood to the right parietal lobe that is thought to be critical inattention and selection. • Symptoms:– Failure to acknowledge objects in the field contralateral to the lesion• Often no perceptual deficit– Neglect patients still activate visual regions in occipital lobes that they claim not to be awarePatients may:• fail to dress the left side of their body• disclaim “ownership” of left limbs• not recognize familiar people presented on the left side• deny the illness Neglect of the Visual FieldNeglect of the Visual FieldDifficulty crossing out itemsDifficulty copying items55 y.o. right handed male R TPJ infarct (Mesulam, 2000)Marshall and Halligan, 1993Patients can neglect the left side of the object, rather than the left side of space. Black lines show expected left-sided person-centred versus red lines showing actual point where the patient neglected Visual neglect syndrome can be object-basedControl Neglect patientVisual neglect syndrome can be object-based• Patient with object neglect cannot detect differences on left side of an object even when falling into right side of spaceDriver and Halligan (1991)Visual neglect syndrome can be object-basedWhen a right neglect patient is shown a dumbbell that rotates,the patient continues to neglect the object that had been on theright, even though it is now on the left (Behrmann & Tipper, 1999).5Simultanagnosic (Balint Syndrome) patients only attend to one object at a timeSimultanagnosic patients cannot judge the relative length of twolines, but they can tell that a figure made by connecting the endsof the lines is not a rectangle but a trapezoid (Holmes & Horax, 1919).Balint patients can only attend to one object at a time even if they are overlappingLuria,