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Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai
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Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Jan 19, 2016

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Page 1: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Longer or Shorter?

An examination of line length discrimination using manipulated feedback

Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai

Page 2: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Outline

1) First steps and hypothesis generation– The Peter Jansen paradigm– Failures and revisions– The Vertical-Horizontal Illusion

2) Experimental Design3) Results4) Conclusions

Page 3: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

The Peter Jansen Paradigm

• The original task flashed two lines on screen simultaneously and asked if the second line was longer or shorter

• This experiment served as the starting point in our research program

Page 4: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

The Original Motivation

• What is the effect of attention on our line length acuity in the Peter Jansen paradigm?

• Could attentional cueing lead to increased performance on a length discrimination task?

• Would an invalid cue decrease performance?

Page 5: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

A Snag in the Literature

• A disturbing picture began to emerge

• Many articles described the “well known fact” that vertical lines are perceived as longer than horizontal lines

Page 6: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

The Vertical-Horizontal Illusion

• When a horizontal line and a vertical line of the same length are presented together, the vertical line is perceived as on average 10% longer

Page 7: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Craven (1993)

• Systematically examining the perception of

Page 8: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

The New Design

• We decided it was unlikely that cuing would cause a significant change in like acuity if our perceptions are already biased

• But what if we could change the perception of the illusion?

• How might you go about designing an experiment to manipulate

Page 9: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Programming a Pilot Run

• We decided to program our experiment from scratch in Matlab due to prior experience

• After extensive tweaking, Amanda and Melanie ran as control subjects

• The result NO vertical-horizontal illusion was present!

Page 10: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Back to the Drawing Board

• After our initial failure, we began to scour journal articles to find an ex

Page 11: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Vertical-Horizontal Illusion

• Vertical-Horizontal Illusion (V-H)– Perception of vertical lines as longer than

horizontal

Page 12: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Purpose

• Increase or eliminate vertical-horizontal illusion

Page 13: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Idea Generation (edit)

• Consecutive lines• Cues– Same/different– Shorter/longer

• Feedback– Correct– biased

Page 14: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Herzog and Fahle, 1999 --Vernier Task

Page 15: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Hypothesis

• Valid feedback– Decrease V-H

• Biased feedback– Increase V-H

Page 16: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Method

• Conditions– Reduction: valid feedback– Control: no feedback– Strengthened: biased feedback

Page 17: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Method

• Blocks (Phases)– Block 1: establish baseline threshold– Block 2: learning trials– Block 3: examine the effect of learning trials

compared to baseline threshold

Page 18: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

DesignBlock 1Block 1 Block 2Block 2 Block 3Block 3

ReductionReduction No No feedbackfeedback

Valid Valid feedbackfeedback

No No feedbackfeedback

ControlControl No No feedbackfeedback

No No feedbackfeedback

No No feedbackfeedback

StrengthenStrengtheneded

No No feedbackfeedback

Biased Biased feedbackfeedback

No No feedbackfeedback

Page 19: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Method

Page 20: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Method

Page 21: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Method

• Subjects– 8 subjects

• Stimuli– Vertical/horizontal lines between -9 to +3 pixels

Page 22: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Method

• Measure– Accuracy of the responses

• Trials– 10 practice trials– 240 trials for each block– 20 trials per length per block– Total of 720 trials

Page 23: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Method

• Procedure– Fixation cross– Mask– Stimulus– Response: left or right

Page 24: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

+

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+

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Page 30: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

ResultPhase 1Phase 1 Phase 3Phase 3 DifferenceDifference

Condition 1Condition 1

Subject 1Subject 1 -3.2651-3.2651 -2.66190-2.66190 1.60321.6032

Subject 2Subject 2 -3.1660-3.1660 -2.5070-2.5070 0.65900.6590

Condition 2Condition 2

Subject 3Subject 3 -3.2703-3.2703 -4.0302-4.0302 -0.7593-0.7593

Subject 4Subject 4 -3.8623-3.8623 -4.4380-4.4380 -0.5757-0.5757

Subject 5Subject 5 -3.5175-3.5175 -3.5103-3.5103 0.00720.0072

Condition 3Condition 3

Subject 6Subject 6 -3.3370-3.3370 -4.0723-4.0723 -0.7353-0.7353

Subject 7Subject 7 -2.1695-2.1695 -1.8156-1.8156 0.35390.3539

Subject 8Subject 8 -5.6957-5.6957 -3.8027-3.8027 1.89301.8930

Page 31: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Results (Condition 1)

Page 32: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Results (Condition2)

Page 33: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Results (Condition 3)

Page 34: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Results

• Replicated the v-h illusion• Inconclusive results in reducing/

strengthening the illusion with valid/biased feedback

Page 35: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Discussion

• Finding 1: Vertical-horizontal illusion was replicated– Craven (1993)

Page 36: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Discussion

Finding 2:• Unable to decrease illusion using valid

feedback

Finding 3:• Unable to increase illusion using biased

feedback

Page 37: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Discussion

Source of error– Number of trials– Number of N

Page 38: Longer or Shorter? An examination of line length discrimination using manipulated feedback Amanda Hostiuc, Alicia Kim, Melanie Laking, and Matt Pachai.

Discussion

Suggestions for future research– More time to train/learn– More trials for Block 2– Better incentive