IN IN LI LINE E AN AND BAR D BAR GRA GRAPH PHS: S: UNDE - - PowerPoint PPT Presentation

BI BIAS ASED ED AVER ERAGE GE PO POSIT ITION ION ES ESTIMA IMATES TES IN IN LI LINE E AN AND BAR D BAR GRA GRAPH PHS: S: UNDE DERES RESTIMA TIMATION, TION, OVER ERES ESTIMA TIMATION, TION, AN AND D PE PERCEPTU EPTUAL AL PU PULL LL

Cindy Xiong, Cristina R. Ceja, Casimir J.H. Ludwig, and Steven Franconeri

Bia ias

■ Bias in position channel ■ Position is believed to be the most precise way to encode information ■ Data encoded in position is assumed to be perceived in an unbiased manner

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Ex Experient perient Setup Setup

■ Two types of data series ■ Uniform or Noisy

Line Bar

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Ex Experient perient Setup Setup

■ Display Frame and Display Types

140 9.6 9.6 x 2.8 in 538 x 140 pixels 140

TOP BOTTOM

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Ex Experient perient Pr Procedures

• cedures

140 9.6

+

Fixation (500 ms) Cue (500 ms)

top/bottm line/bar

Stimulus Display (500 ms) Mask (500 ms) Response (Until Response)

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Ex Experient perient 1

■ How accurately people can perceive average position of a single line or single set of bars in a graph? ■ Establish a baseline for later experiments ■ 576 trials, 288 trials for each line and bar position estimate, with half of trails for each condition displaying noisy and uniform data.

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Ex Experient perient 1 R 1 Results esults

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Ex Experient perient 1 R 1 Results esults

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Ex Experient perient 1 R 1 Results esults

■ Underestimation of Lines

– regardless appeared top or bottom, although more underestimation at the bottom – not depend on whether the line was noisy or uniform, although estimations of uniform data are more accurate and precise – not an artifact of poor average strategies (not averaging only high points and low points) – initial probe position affects error but not bias

■ Overestimation of Bars

– same results as the lines’

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Ex Experient perient 2

■ How this bias affected by the presence of an additional data series?

– two lines (“compound line-line”) – two bars (“compound bar-bar”)

■ 240 trials, 120 trials for each line and bar average position estimation condition. ■ 144 control trials (experiment 1) were replicated.

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Ex Experient perient 2 R 2 Results esults

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Ex Experient perient 2 R 2 Results esults

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“Perceptual Pull”

■ Underestimation of top line was exaggerated ■ Underestimation of bottom line was reduced ■ Overestimation of top bar was reduced ■ Overestimation of bottom bar was exaggerated

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Ex Experient perient 3

■ What determines the extent of perceptual pull? (Data-series? Perceptual similarity? ) – “compound line-bar”, “compound bar-line” ■ Experiment 1 and 2 results were replicated.

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Ex Experient perient 3 R 3 Results esults

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Ex Experient perient 3 R 3 Results esults

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Ex Experient perient 3 R 3 Results esults

■ The effect of perceptual pull occurs across graphed data series types. ■ Strength of pulling across data series types?

– Extent of perceptual pull does not depend on data series type

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Conclusions

• nclusions an

and d Ge General neral Gu Guidel ideline ine

• 1. Underestimation of lines and overestimation of bars
• 2. “Perceptual Pull”:
• presence of an irrelevant line or set of bars in

the same display pulled average position of estimations of a target line or set of bars toward the position of this irrelevant data series.

• 3. Perceptual pull is not dependent on graphed data

series type.

• 1. Using bars to display data
• 2. Avoiding plotting two series in the same display

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Criti ritique ue

■ Strengths

– An area few have studied – Carefully designed experiments, considered potential causes and issues – Well planned future works

■ Weaknesses/Limitations

– Short observation time (500ms) – Small experimental population

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THANK YOU

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Li Limitations mitations

■ Asymmetrical Biases ■ Aspect Ratio ■ Figure-Ground Encoding ■ Take Beyond Averaging ■ Reporting Mechanisms ■ Complex Real-World Stimuli ■ Untested Encodings

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Ex Experient perient Setup Setup

■ Three Mean Values (for each top and bottom section)

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Bia ias

Ebbinghaus Illusion (perceptual) Is the population of Nova Scotia more or less than 200,000?I Anchoring Effect (cognitive)

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