The life-span trend in the magnitude of the Mueller-Lyer illusion as a function of hue and age

Dentists make larger holes in teeth than they need to if the teeth present a visual illusion of size

BACKGROUND

Health care depends, in part, on the ability of a practitioner to see signs of disease and to see how to treat it. Visual illusions, therefore, could affect health care. Yet there is very little prospective evidence that illusions can influence treatment. We sought such evidence.

METHODS AND RESULTS

We simulated treatment using dentistry as a model system. We supplied eight, practicing, specialist dentists, endodontists, with at least 21 isolated teeth each, randomly sampled from a much larger sample of teeth they were likely to encounter. Teeth contained holes and we asked the endodontists to cut cavities in preparation for filling. Each tooth presented a more or less potent version of a visual illusion of size, the Delboeuf illusion, that made the holes appear smaller than they were. Endodontists and the persons measuring the cavities were blind to the parameters of the illusion. We found that the size of cavity endodontists made was linearly related to the potency of the Delboeuf illusion (p<.01) with an effect size (Cohen's d) of 1.41. When the illusion made the holes appear smaller, the endodontists made cavities larger than needed.

CONCLUSIONS

The visual context in which treatment takes place can influence the treatment. Undesirable effects of visual illusions could be counteracted by a health practitioner's being aware of them and by using measurement.

Real space and represented space: Cross-cultural perspectives

This paper examines the contribution of cross-cultural studies to our understanding of the perception and representation of space. A cross-cultural survey of the basic difficulties in understanding pictures—ranging from the failure to recognise a picture as a representation to the inability to recognise the object represented in the picture— indicates that similar difficulties occur in pictorial and nonpictorial cultrues. The experimental work on pictorial space derives from two distinct traditions: the study of picture perception in “remote” populations and the study of the perceptual illusions. A comprison of the findings on pictorial space perception with those on real space perceptual illusions. A comparison of findings on pictorial space perception with those on real space perception and perceptual constancy suggersts that cross-cultural differences in the perception of both real and representational space involve two different types of skills: those related exclusively to either real space or representational space, and those related to both. Different cultural groups use different skills to perform the same perceptual tasks.

Susceptibility to illusions and cognitive style: implications for pharmacy dispensing

Response distributions for five cognitive illusions and one visual illusion were examined in two samples, college students (n = 134) and pharmacists (n = 51). These illusions were selected for study on the basis of pharmacists' judgments about associations of illusions to common dispensing errors. Participants were categorized as Illusion-prone or Illusion-resistant, and distributions of such tendencies for the six stimuli used varied within samples. Significant differences between the two samples on illusion-proneness and resistance were observed for the "Moses' Ark" and -Fcount" illusions. Associations of Illusion-prone and Illusion-resistant responses to field-dependence, psychological type, and the cognitive orientations derived from Psychological Type Theory were examined. Field-independence-field-dependence was the only cognitive dimension associated with Illusion-prone and Illusion-resistant responding. Implications of the data for developing measures based upon visual and cognitive illusions to identify people with error-prone tendencies were discussed.

Note on the ontogeny of assimilative illusions: a reply to Pressey (1987)

It is argued that a previous study showing the parallel lines illusion is stronger in adulthood than in adolescence or old age is methodologically sound. Further, this finding does not necessitate a defense of assimilation theory based on epistemology that links the phenomenal properties of illusions to the techniques of measurement. Rather, it is suggested that Pressey's 1974 and 1987 hypothesis that all illusions of assimilation decline from childhood to adulthood mistakenly extends the decrement into adulthood when in fact the decrement occurs only between the ages of 6 and 10 years.

The effect of lightness contrast on the colored Müller-Lyer illusion

Two subjects estimated the length of the central line in red and blue Müller-Lyer figures that were viewed both foveally and parafoveally. The illusion figures were defined by either lightness and hue differences between figure and ground or by a hue difference alone. For both subjects, the figures defined solely by hue produced larger illusions. Since depth-cue scaling and other cognitive factors did not cause the enlargement, it was concluded that the robust, hue-produced illusions resulted from contour interactions generated within parvocellular channels that are specialized for coding color.

Simulated aged performance on the embedded figures test

According to Labouvie-Vief (1985) the predominant explanatory mechanism for performance decline among the elderly incorporates a regression-oriented view of cognitive development: The present study tested the hypothesis that age-related performance decline may be explained by the quantitative changes in lower-level visual functions, such as those due to preretinal aging, which preclude the expression of intact cognitive (qualitative) processes. Thirty undergraduate female volunteers (18 to 25 years) viewed the Embedded Figures Test (EFT) under three conditions: no-filter viewing, .6 neutral-density filter viewing, and simulated-aged (yellow-filter plus .5 neutral-density filter) viewing. A one-way ANOVA revealed significant viewing condition effects for the number of items solved, the number of errors, and time-to-solution. Significant linear trends were found for levels of luminous transmittance. Results supported the hypothesis that preretinal aging appears to degrade EFT performance.

The magnitude of the Mueller-Lyer illusion as a function of hue, saturation, fundus pigmentation, and simulated aging

Ninety-six female college students were tested to determine the effects of hue, saturation, fundus pigmentation, and simulated aging on the magnitude of the Muller-Lyer illusion. In the first experiment, main effects for hue and saturation as well as an interaction effect between them were found to be significant. In the second experiment, filters served to simulate receptor aging by decreasing the visual sensitivity of young adults. A significant main effect of hue and an interaction effect between hue and saturation were found. However, there was no significant effect for fundus pigmentation in either experiment. Comparative analysis of the two experiments showed that only the magnitude of the illusion produced by an unsaturated blue figure decreased significantly when viewed through aging-simulation filters.