Home > Methodology, The Face > It Can Be In How You Look At It….

It Can Be In How You Look At It….

Krupinski et.al. (2005) found that the use of LCDs to view radiographic images degrades reader performance. This work has led me to wonder if variation in human seated height, combined with the use of LCDs to present stimulus sets, might have a confounding effect on attractiveness research.

Liquid Crystal Displays – LCDs – are becoming increasingly common as computer monitors. I just checked an online electronics retailer and could not find a single CRT monitor for sale. LCDs are smaller, lighter, can last longer, and use less energy than CRTs – so the transition to the newer technology makes sense. Each type of technology has pros and cons, and there are significant performance differences between manufacturers and models. One consistent limitation of LCDs, however, is limited viewing angle: color and brightness changes occur as viewers move off-axis. Technological improvements have resulted in increased viewing angles in the latest, high-end LCDs. However, most of the improvement has been in the lateral rather than in the vertical direction. This image shows typical, vertical angle of view effects on a higher end laptop LCD screen.

LCD-Viewing-Angle-Variation

Left: iphone snap from a viewing angle of approximately 0°; Middle: snap from below; Right: snap from above.

Some observations:

  • Viewing from below primarily darkens the image while viewing from above lightens it
  • Viewing from below darkens the skin and increases contrast
  • Viewing from below can add more dimensionality to a face
  • Viewing from above primarily lightens the skin while decreasing contrast and dimensionality

While just rules of thumb, darkening the skin and increasing contrast are both masculinity enhancing photographic techniques. Lightening the skin and decreasing contrast are femininity enhancing techniques. Adding dimensionality is a technique used to make subjects appear to weigh less. Given that sexual dimorphism and apparent body mass are relevant to evaluations of attractiveness, I suggest that beauty researchers who use LCDs take steps to minimize possible confounding effects of variation in seated height when presenting stimuli on LCDs. As an initial suggestion, perhaps all subjects in beauty studies that utilize LCDs should be positioned to maintain a 0° angle between raters’ eyes and stimulus-image eyes? Possible approaches include:

  • Use of a chin rest (the technique used by Dr. Rhodes and colleagues (2007) in the study from which this image was taken)
  • Use of adjustable height seating
  • Use of adjustable height monitors

Additionally, research to investigate whether there is a measurable effect of seated height on attractiveness ratings (with LCD presentation) seems called for.

Cautions

  • Not all images will show this degree of off-axis variation
  • LCDs will show more or less off-axis variation than is visible here: each make/model is different

In closing, I will emphasize that the variations in the image above involve alterations of viewing angle that are substantially greater than would be expected given the variation in adult human seated height. Therefore, under normal research conditions the effect will not be as dramatic. However, in most/all LCDs, alterations in vertical viewing angle begin to show these changes rather quickly.

Wayne Hooke
ResearchBlogging.orgKrupinski EA, Johnson J, Roehrig H, Nafziger J, & Lubin J (2005). On-axis and off-axis viewing of images on CRT displays and LCDs: observer performance and vision model predictions. Academic radiology, 12 (8), 957-64 PMID: 16023384

Rhodes, G., Peters, M., & Ewing, L. (2007). Specialised higher-level mechanisms for facial-symmetry perception: Evidence from orientation-tuning functions Perception, 36 (12), 1804-1812 DOI: 10.1068/p5688

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Categories: Methodology, The Face
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