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Blind Procedures

Blind Procedures

Ideally, the people who observe and record the children’s behavior are unaware of who was assigned to the experimental or control group, in order to control for experimenter bias. Experimenter bias refers to the possibility that a researcher’s expectations might skew the results of the study. Remember, conducting an experiment requires a lot of planning, and the people involved in the research project have a vested interest in supporting their hypotheses. If the observers knew which...

The Placebo Effect

The Placebo Effect

The placebo effect occurs when people's expectations or beliefs influence or determine their experience in a given situation. In other words, simply expecting something to happen can actually make it happen.

Blinding

Blinding

Blinding is a commonly used method of not telling participants which treatment a subject is receiving. Blinding is a critical part of a randomized control trial or RCT. It reduces the bias that affects the results. In an RCT, blinding is used in the form of a placebo. A placebo effect occurs when untreated subjects falsely believe they have received the treatment and report improved symptoms. A placebo or a dummy treatment is administered to subjects to negate the bias caused by such an effect.

Focusing of Light in the Eye

Focusing of Light in the Eye

Light rays enter the eye through the cornea, a transparent dome-shaped tissue that is the eye's outermost layer. The cornea bends or refracts, light rays traveling to the pupil. The shape of the cornea determines how much of the light is bent and whether the image will be focused correctly on the retina at the back of the eye. Once the light has passed through both refraction layers, it converges into a single focal point onto a small area. This is where photoreceptors start transforming...

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Related Experiment Video

Updated: Sep 8, 2025

Stereoacuity Improvement using Random-Dot Video Games

Stereoacuity Improvement using Random-Dot Video Games

Published on: January 14, 2020

Flickering lenses enhance reading performance through placebo effect.

Sandro Franceschini¹, Giovanna Puccio¹, Sara Bertoni²

¹Developmental and Cognitive Neuroscience Lab, Department of General Psychology, University of Padua, Padua, Italy.

Psychological Research

|July 8, 2025

Summary

Positive expectations, or placebo effect, significantly improved reading accuracy in children with developmental dyslexia (DD). This effect was larger than traditional training programs, questioning the real efficacy of current DD interventions.

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Area of Science:

Neuroscience
Developmental Psychology
Educational Psychology

Background:

Developmental dyslexia (DD) is a common neurodevelopmental disorder.
Traditional DD remediation often lacks placebo control, suggesting expectation bias may influence outcomes.
Expensive interventions like flickering glasses claim significant reading improvements.

Purpose of the Study:

To investigate the placebo effect and efficacy of flickering glasses on reading performance in children with DD and adults.
To compare the impact of positive expectancy on reading skills across different reader groups.

Main Methods:

A double-blind, within-subject experimental design was employed.
Two experiments included children with DD (n=49) and unselected young adults (n=48).
Reading accuracy and pseudoword decoding speed were measured under placebo and control conditions.

Main Results:

Positive expectancy (placebo effect) enhanced word reading accuracy in children with DD, exceeding effect sizes of standard training.
Adult poor readers showed similar improvements in reading accuracy.
Typical readers improved only in pseudoword decoding speed.
Flickering glasses reduced the lexicality effect and predicted pseudoword decoding in children with DD.

Conclusions:

The placebo effect plays a substantial, underestimated role in developmental dyslexia interventions.
Findings challenge the efficacy of standard dyslexia training programs.
Further research is needed to disentangle true treatment effects from placebo responses in DD interventions.