2  Eye-tracking during reading

What can we learn from the measures?

Author

Affiliation

Daniela Palleschi

Humboldt-Universität zu Berlin

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3 Eye-tracking

• in (psycho)linguistics
  • during reading
  • visual world paradigm
• in psychology
  • pupillometry
  • visual search
• but also
  • market research
  • diagnostic tool

3.1 Eye movements

• saccades: eye movements (e.g., from one word to another)
  • average saccade legnth: 7-9 letters (in alphabetic writing systems)
• fixations: ‘looking at’ something, e.g., a word (little movement)
  • when information is taken in
  • average duration: 225-250ms (ranging 50-600ms)
• regressions: saccades to earlier text
  • occurance: 10-15% of saccades in skilled readers

(rayner_eye_2009-1?)

3.2 The eye-tracker

• eye-tracker
  • camera \(+\) infrared illuminator
• screen
• chin/head rest
• in our lab: desk-mounted

Image source: SR Research (all rights reserved)

4 Eye-tracking during reading

4.1 Eye-tracking reading measures

• inform theories of language processing via linking hypotheses
  • linking visual attention to processing
• typically, we compare reading times as a function of some manipulation
  • e.g., Sally went/goed to the store.
• longer reading times are taken to reflect processing costs, associated with e.g., sentence complexity or anomalies

4.2 Region of interest (ROI)

• can be anything on-screen
  • sentence-level
  • word/region-level
  • a certain part of the screen

4.3 Measures (dependent variables)

• what we measure = dependent variables (usually…)
  • their value depends on some predictor (e.g., word frequency)

• measures of duration (time spent on a region)
  • first fixation
  • first-pass reading time
  • regression path duration
  • total reading time
• data type: continuous

• measures of revisits
  • number of fixations
  • number of regressions in/out
  • regression in/out (yes or no)
  • probability of regressions in/out (0:1)
• data type: binary (0,1) or count

4.4 Independent variables

• what can influence reading measures? (juhasz_lexical_2011?; rayner_linguistic_2011?; warren_influence_2011?; clifton_syntactic_2011?)
  • some examples:

• Word properties
  • word frequency
  • word length

• Sentence-level influences
  • context (i.e., prediction)
  • semantic or grammatical manipulations

• Inter- and intra-individual
  • domain-specific expertise
  • reading skill level

4.5 What do these measures tell us?

• eye-tracking during reading can tell use when and where processing costs are incurred
• early measures involve “first contact with a word” or region: first-fixation, first-pass reading time (vasishth_what_2013?)
• late measures involve regressions to a region: e.g., total reading time
  • may also include ‘spillover’ effects from early processing
• eye-tracking during reading measures can therefore tell us about stages of processing

References