Prof. Greg Francis 5/27/081AttentionIIE 269: Cognitive PsychologyGreg FrancisLecture 13Should you pay $59.95 for Mega-speedreading?Attention We saw last time that attention can havevery powerful effects when it is focused on one thing, you ignoreother things Today we want to consider some morespecific properties of attention and look at experimental methods that areused to study attentionCharacteristics of attention By identifying the properties andcharacteristics of attention we can deduceproperties of the underlying systems thatare involved in cognition whether attention is thought of as a “system” or as a by-product of other systems Look at temporal featuralAttentional blink Suppose you have to identify rapidly presented (100ms) letters e.g., detect J and/or K in a stream of lettersMPKRWSAttentional blink Turns out that detection of first letter tends to makedetection of the second letter very difficult if it immediately follows the first Attentional blinkMPKRJSAttentional blink Measure frequency of detection get a curve like this (my CogLab data) compare to group dataImplies thatdetecting firstletter causes you to misssecond letter!Prof. Greg Francis 5/27/082Attentional blink Measure frequency of detection class data (72 observers)Implies thatdetecting firstletter causes you to misssecond letter!Attentional blink Suggests that processing the first targetletter, “J” uses up resources that would otherwise be usedto process second target letter, “K” attentional focus and refocus takes time and forthis task takes approximately 400 msSLNBJRKH...JOnce processing is done (afew hundred milliseconds),there is no difficultydetecting second letter.Attentional blink You could use the same type of approachto find the time course of attentionalprocessing with other stimuli shapes numbers colors faces Flowers spiders...Speed reading Ever seen the ads for speed reading? One is for a book called Mega Speed Reading claims to teach you to read 25,000 words per minute ==> 2.4 milliseconds for each word impossible, if only by attentional blink! The seller is skimming at best, and lying at worstVisual search Find the mistake in this sign Much of our time is spent looking for variousthings Staplers Road signsVisual search Time and type of processing can also be measured byhaving observers respond as quickly as possible whenthey detect a target hypothesize that tasks that involve attention will beslower than “perceptually” based tasks expect attention to depend on the number of things thatmust be searched Typically, we distinguish between a target anddistracters by one or more features we vary the number of distracters and measure reaction timeProf. Greg Francis 5/27/083Feature search When the target differs from all the distracters by onefeature (color, shape, size, orientation motion,…) which feature difference leads to fast detection of the target? does it depend on the number of distracters?Color Orientation ShapeConjunctive search When the target differs from all the distracters by onefeature (color, shape, size, orientation motion,…) but thedistracters also differ target is the conjunction (intersection) of features which feature differences lead to fast detection of the target? do they depend on the number of distracters?Color/shape Orientation/Color Shape/orientationImpressions Feature searches (at least for right features) effortless target “pops-out” at you reaction time does not vary with the number of distracters Conjunctive searches (at least for right features) effortful requires you to examine individual stimuli and determine ifthey are the target keep searching until you find the target and then hit theresponse key reaction time does vary with the number of distractersVisual search The data support these impressions with strong quantitative validation Four types of responses 1) Feature - present (can respond as soon as see target) 2) Feature - absent (must examine all stimuli before suretarget is not present) 3) Conjunctive - present (can respond as soon as seetarget) 4) Conjunctive - absent (must examine all stimuli beforesure target is not present)CogLab feature search Few distracters -easyCogLab feature search Many distracters - still easyProf. Greg Francis 5/27/084Conjunctive search Few distracters - fairly easyConjunctive search Many distracters - difficultVisual search My data from CogLab compare to group CogLab dataVisual search group CogLab data (69 observers)Visual search Interpretation Feature searches do not vary with number of distracters» feature searches “pop-out,” the distracters are irrelevant Feature present = feature absent» no searching is required, the reaction time just reflectsthe time to make the response Conjunctive searches increase RT with number of distracters» must search individual items and compare with target tosee if it matches, each comparison takes time (attention) Conjunctive absent > conjunctive present» must search through more items (on average twice asmany) for absent than present searches There are thousands of variations of visual searchexperimentsInterpretation Feature maps: color, shape Feature search can identify target within either feature mapShapeColorbluegreencornersarcsProf. Greg Francis 5/27/085Interpretation Feature maps: color, shape Feature search can identify target within either feature mapShapeColorbluegreencornersarcsInterpretation Feature maps: color, shape Conjunctive search cannot identify target within either feature map aloneShapeColorbluegreencornersarcsRequirescomparisonacross featuremapsSerial processthat takes timeInterpretation Feature maps: color, shape Conjunctive search cannot identify target within either feature mapShapeColorbluegreencornersarcsRequirescomparisonacross featuremapsSerial processthat takes timeAutomaticity When a task is unfamiliar it seems torequire a lot of attention to perform Later it requires less attention riding a bike driving a car typing tying shoelacesAutomaticity The process whereby a task goes fromrequiring a lot of attention to requiring little iscalled automatization Many tasks are automatizable color naming word naming Can measure effects by pitting