Chapter 1. Gestalt Perception

1.1 Introduction

Look at the following figure. What do you see?

Most people report seeing columns, but it is really just a collection of dots. The perception of columns comes from the fact that the dots are closer to each other vertically than they are horizontally. This finding is just one of the interesting features about perception that was discovered and systematized by the Gestalt psychologists early in the 20th century into what is known as the Gestalt Laws of perception. We group together disconnected bits of a scene into a more complete perception. This is quite useful in the real world because one object often overlaps part of another object, so we need to be able to group these unconnected parts of objects together.

One classic illusion -- the Kanizsa Illusory Contours -- is shown below.

Most people see a triangle overlapping three circles. Of course, there is no triangle, just slices out of the three circles. These circles are often called Pac-Man figures because of their similarity to the character in the classic video game of the same name. The current experiment will examine how this illusion arises.

Kanizsa, G. (1979). Organization in Vision: Essays on Gestalt Perception. New York: Praeger.

1.2 Experiment Setup

Figure 1.3

1.3 Instructions

You will need to press the space bar to begin the experiment. At the beginning of each trial, a fixation mark will appear. Keep your eyes positioned on this mark as much as possible. A figure will flash around the fixation mark. This is called the prime stimulus. Then, following a brief blank period, when just the fixation mark is present, two shapes will be presented. One shape will be on either side of the fixation mark. The shapes will be either squares or triangles. Your task is to determine if the figures are the same or different. You may respond by using the buttons below the images or the keyboard.

Keyboard Responses:

1.4 Experiment

Figure 1.4

1.5 Results

Figure 1.5

1.6 Quiz