Krejtz, Izabela

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LEAD-ME Summer Training School Warsaw’21Eye tracking in media accessibility research - methods, technologies and data analysesIntroduction to experimental designs in eye tracking studiesIzabela Krejtz Eye Infoby looking into eyes we can recognize their owner.A BC DWhose eyes are these?Whose eyes are these?By analyzing eye movements we can tell what a person is doing and possibly infer their mental statesDuchowski et al. (2016)PROCESSING VISUAL INFORMATIONViewing path for 1 person while viewing the image (30 sec.)Fixations (circles) saccades (lines) Visual exploration from eye movements perspectiveis a consecutive sequenceof fixations and saccades Fixations stabilise image on retina low spatial disparity Saccades move eye towardsa new location high speed and amplitudeStudy designwhat who howBefore designing a study we need to decide: What to study: Perception of emotions  Who will be participating:  Deaf and hearing individuals  How will we test our prediction: Presentation of faces expressing emotionsDo we have any predictions?HOW:Research designs correlational design looking for relationship between two or more variables natural groups design (quasi-experimental) independent variable is not manipulated experimental design independent variable is manipulated random allocation to groups control of confounding variables Decision treeResearchdesignsQuantitave IVCorrelationalQualitative IVNatural groupsExperimentalBetween groupsWithingroupsMixedNatural groups designquasi-experimentalmixed-designWHAT: Perception of emotionsWHOGroupHearing vs Deaf1st IVindependent variablenot manipulatedbetween-subjectsHOWFaces Happy vs Angry2nd IVindependent variablemanipulatedwithin-subjectsHOWVisibilityFull vs Half face3rd IVindependent variablemanipulatedwithin-subjectsStudy design2x2x2mixed design So far, our study has 3 independent variables each on 2 levels Independent variables can be introduced as: Between-subjects designs require more participants (around 20 per group) than within-subjects designs Within-subjects designs require less participantsbecause each participant is presented with the same set of stimuli Mixed design has at least one within-subjects and one between-subjects independent variable We can complicate the design either by adding more levels to IVs or adding more independent variablesFinal study design:3x3x2 mixed designfull            half              full              half              full              half happy                              sad                               angryDESIGNING AREAS OF INTERESTIn eye tracking studies, areas of interests often create another within-subjects independent variableDRAWING AREAS OF INTERESTEach stimulus is a separate AOIangry sadhappy neutralKrejtz et al. 2018 Journal of Clinical PsychologyWe may analyze: The proportion of time spent looking at each of stimulus  in relation to the rest of stimuliFFD - First Fixation Duration First  Glance DurationTotal Dwell Time Other metricsangryhappyKrejtz et al. 2018Examples of individualscanpaths Depressed before and after therapy (mindfulness training)FOUR-WORD PROCEDUREEye tracking indices 12 slides with four words on each of them was shown to participants dysphoric  aversive positive neutral  simultaneously presented on a slide for 10 seconds indices of attentional bias: glances count and dwell time of dysphoric wordsEllis et al. 2011 ET indicators and everyday functioningProportion of dwell time on negative words as a predictor of daily functioning of depressed individualsDWELL TIME on DYSPHORIC WORDSPredictorof daily rumination:dwell time on affective wordsMultilevel model Day LevelRumination ij = β0j + rijPerson Level β0j = γ00 + γ01* (Dwell Time) + u0jdysphoric positive aversive neutralRumination .36** .04 .63** .20Adjustment -.21** -.08 -.21* -.14Holas, Krejtz et al. 2019. Emotion and CognitionThe effect of consumer confusion onattention to products placed in TV showsExperimental mixed design 2x5:1 Between-subjects independent variable (manipulated)1 Within-subjects IV (epoch)Study designGroup 1: noise3-min. videoGroup 2: calm5-min culinary program"Advisor of taste" „Doradca smaku”Grochowska, Kulig et al.  (in prep.)Brands in the TV showDynamicalAOIsDistribution of attentionNumber of fixationson the placedproductsp=0.005Distribution of attention during perception of a sign language interpreterAbramczyk et al. unpublished2x3 within-subjects design:1IV: lip movement2IV: type of sign languageHow attention is distributed between face and hands depending on sign language and lips movementHow attention is distributed between face and hands depending on sign language and lips movement Type of Sign LanguagePSL Hybrid SLSlips movementyes yes yesno no noA little bit of a theory Theory of compensation – hearing impairment strengthensvisual attention(Gibson et al., 1969)  Deaf are more attentive to movements in their peripheral visualfield than the Hearing lack of support for the general enhancement of visual attentionamong Deaf(Armstrong et al. 2002; Pavani, Bottari, 2012)source: http://www.ncbi.nlm.nih.gov/books/NBK92865/Guess which recording is from deaf participants and which one is a recording of hearing individuals fluent in sign language Long-term Music Education Fosters Attentional Control in Primary School ChildrenMixed design:Between-subjects independent variable (natural groups)Within-subjects IV (experimental task)Within-subjects IV (time of measurement)Music educationand attentionalcontrolProcedure:Cybulska et al. submittedexemplary scanpathin antisaccadic trialAOIs in antisaccade taskResults:significant decrease in reaction timethe linear trends are steeper for music childrendue to a shorter latency of 1st saccade toward target latencyof 1st saccadetowardtarget experimental design2x2effect of word characteristic on cognitive effortCHI'21 workshop on "Eye Movements as an Interface to Cognitive State"Exemplary scanpathsCHI'21 workshop on "Eye Movements as an Interface to Cognitive State"UNITS OF ANALYSISIN READING STUDIESWe may analyze eye movements over: whole text, paragraph, sentence, word, syllable, letterAOIs IN READING RESEARCHA more common method of determining AOIUsed for longer textsA comparative reading study reading in typically developing  and dyslexic  childrenfixation, regressions, refixations, skippingReading music notes Transitions between AOIsReading film subtitlesKrejtz, Szarkowska et al. 2016Transitionmatrix:analysis of the probability of switching between AOIsImageSubtitle beginning Remaining subtitle areaKrejtz, Szarkowska & Krejtz, 2013EYE TRACKING RESEARCH CENTER ESTABLISHED IN 201424 VIDEO EYE TRACKERS 11 GAZE POINTS, 60 Hz4  GAZE POINTS, 150 Hz1 SMI RED, 120 Hz7 PUPIL LABS, 120Hz1 EYELINK 2000 HzEye tracking in the wildJoint collaboration projectJoint attentionin collaborationproject of Katarzyna Wisiecka,  PhD candidateMobile eye tracking with PupilLabseyetrackersJoint attentionin collaborationMobile eye tracking with PupilLabsJoint attentionin collaborationMobile eye tracking with PupilLabs eyetrackersprecision and accuracyan example of bright pupil and corneal reflection  illuminated by infra-red light of Gaze Point 3 eye trackerPUPIL ANDCORNEAL REFLECTIONFOR BOTH EYESMantiuk et al.. HOW DOES IT WORK?The corneal reflection of the infrared light source is measured relative to the location of the pupil centerCorneal reflections known as PURKINJE imagesJAN EVANGELISTA PURKYNĚ1787-1869Chech anatomist and physiologistOne of the founding fathers of physiology. He established the first Department of Physiologyin the world at the University of Breslau– in Prussia(now Wrocław, Poland) in 1839.How doesvideo-based eye trackerwork? pupilInfrared light =better pupil distinguishabilityMapping the coordinates of visual scene onto the camera image (callibration) Capture eye image by video cameraPupil detectionEye position estimationTHE ACCURACY OF THE EYE TRACKER defined by the distance between the target and the eye fixation  (typically expressed in angular degrees)+targetgaze pointCalibration errorAccuracyand precisionhttps://www.filamentlearning.com/backyard-engineers-lesson-3-accuracy-and-precisionCALIBRATION -EXAMPLECALIBRATION EXAMPLESVALIDATIONonline eye tracking https://www.realeye.io/Visualization of attention distributionOur team

Experimental Designs in Eye Tracking Studies

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Experimental Designs in Eye Tracking Studies

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