Outline Of An Informative Speech On Optical Illusions

Specific Purpose: To inform my audience optical illusions.

Central Idea: Answering the following three questions -- what exactly optical illusion is, the history of optical illusions and why it occurs – can help people to understand optical illusions.

Introduction

I. Recently, some pictures attracted me, and I feel that they are very magic. After doing some researches, today, I want to share them with you. That’s why I choose this topic.

II. (Show the pictures to audience.) What do you see? And what are you feeling? Disturbed and unbalanced right?

III. This phenomenon is called optical illusion.

IV. Now, I will introduce you what exactly optical illusion is, the history of it and why it occurs.

(Transition: Let’s start with the definition

An optical illusion, which is also called a visual illusion, is characterized by visually perceived images that differ from objective reality. From my perspective, it is a situation that something in the picture are motionless, but you feel it is moving. And then you are confused between the reality and illusion.

B. There are three main types: literal illusions, physiological illusions and cognitive illusions.

1. Literal illusion creates images, which are different from the objects that make them. Artists may use objects such as fruit or foliage to create a portraiture or scenery, like these pictures. (Show pictures to audience)

2. Physiological illusion is the result of excessive stimulation of a specific type, such as brightness, color, size, position, tilt, movement. For example, the afterimages adapt stimuli of excessively longer alternating patterns, just like this picture. (Show picture to audience)

3. Cognitive illusions are the result of unconscious inferences.Take this picture (show picture to audience) for an example. In this picture, you can look at this cylinder in two opposite ways – from right to left or from left to right.

(Transition: Then, let’s learn about the history of optical

According to him, it was the environment that fooled us and not the senses.

C. In addition, the famous Greek philosopher, Aristotle tried to provide some satisfactory answers on this topic.

1. He agreed with Protagoras on the point that we could rely on the senses to obtain a correct picture of reality.

2. However, Aristotle also added that it was possible to fool the senses quite easily. In the course of time knowledge about optical illusions was enriched by different philosophers and researchers.

D. Last but not least, thoughts presented by Plato also provide some insights into this subject matter.

1. According to Plato, deciphering the trickery and ultimately the reality of illusions is possible with the use of both senses and mind.

(Transition: Next, let me inform you the reasons of optical illusions.)

III. There are 2 major guesses why optical illusion occurs.

A. First of all, according to Dale Purves’s article “Visual illusions: An Empirical Explanation “, one logical reason for optical illusions is mistaken judgment.

1. In my opinion, it is like an error in the estimation of distance or depth, which can cause optical illusions.

2. If objects of contrasting colors are placed beside each other, our eyes mistake one color for