Müller-Lyer Illusion

1.1 Müller-Lyer Illusions

Table 1 My errors for the Müller-Lyer (1889) illusion.
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Trial number My errors (mm)
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1 1.5
2 1.5
3 1
4 1
5 0.5
6 0
7 0
8 0
9 0
10 0
Mean 0.55
Standard Deviation 0.64334
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1. A one-sample t-test was performed on the sample of error rates on a perceptual task involving the Müller-Lyer illusion. The t-test showed that the scores were significantly different from zero with a mean error score of (M=0.55), (S. error M=0.20344), (t (9)=2.70, p=0.024). These results support the occurrence of the Müller-Lyer illusion.

Standard error of the mean (0.20344), t-value (t= 2.703), degrees of freedom (df=9) and significance level (p=0.024)

2. In each modality: visual and haptic, the t test compared the error scores from each sample against an ideal error score of zero. Significant p values derived from the t-tests would indicate a significant difference between general means from each modality and the ideal error rate, thus indicating that the Müller-Lyer illusion was present in both modalities.

3. Each data point on the scatterplot represents the mean error rate (in mm) for one participant for both tasks: visual illusion and haptic illusion.

Figure 1 The haptic illusion in mm (mean signed errors) as a function of the visual illusion in each participant (N = 30) and the regression line.

4. The increments for both the vertical and horizontal axis are identical (increasing by 2mm each time), however the physical length between increments for the vertical axis is about half the length for the horizontal axis

5. Equation y = 1.62 + 0.663 x

Where: y = Predicted haptic error x = visual error Predicted haptic error = 1.62 + 0.663 × visual error = 1.62 + 0.663 × 10 = 1.62 + 6.63 = 8.25(mm)

Using the regression equation provided, if a participant made an error of 10mm on the visual illusion, it would be predicted that the same participant would make an error of 8.25mm on the haptic illusion.

Reference:
Gentaz, E., Camos, V., Hatwell, Y., & Jacquet, A-Y , (2004) The visual and the haptic Müller-Lyer Illusions: Correlation Study, Current psychology letters [Online], 13, Vol. 2, online since 05 juillet 2004, connection on 29 mars 2012.

Size and Depth Perception: The Role of Familiar Size and Token Variance

1.2 Common portable objects

2. Haber and Levin (2001) argue that distance perception and size perception are two separate processes, independent of each other and relying on almost non-overlapping information sources, from a cognitive psychology perspective. Distance perception can be defined as; involving judgments of how far away static objects are from an observing within a three-dimensional space (Haber& Levin, 2001). According to Eysenck and Keane (2010), such perception relies on visual cues from our environment. For example the monocular cue of texture explains that details of our environment become less clear as you look into the distance. In contrast, size perception is characterized as involving judgments of how big a static object in terms of its metric mass within a three dimensional space, which is largely dependent upon memory and familiar size of an object rather than relying solely on cues from our environment (Haber & Levin 2001). Evidence for this position was demonstrated in Haber and Levin’s (2001) study, in which