Visual perception

Introduction

Visual acuity is the ability to discriminate different colours, intensities and patterns of light. This does depend in part on the physical make up of cells in the retina, but it also depends on the way that the brain processes the visual signals that it receives. Visual perception is the ability of the brain to interpret incoming signals as information, which may then influence subsequent behaviour.

In this activity we are going to use the term ‘perception’ to mean both the ability to see and interpret visual signals. We will be using a Micro:bit device to display different patterns on the LED display, and challenge the user to decide when there has been a change in pattern.

Into space with the BBC micro:bit | a resource for science teachers STEM Learning operates the National STEM Learning Centre and Network www.stem.org.uk

Visual perception

Space context

Prior Knowledge

Commanding a spacecraft such as Soyuz requires astronauts to have high levels of visual perception. It is important to be able to detect small changes in the various instrument displays that may require immediate attention. Analysis of astronauts visual perception have shown that in a high proportion of astronauts, there is a measurable decrease in visual perception over the course of a space flight, and that this problem gets worse the longer the astronaut stays in space. (See linked articles at the end of this activity). Monitoring visual perception is therefore of great importance for extended space missions such as the Principia mission on ISS and human space flights to Mars.

Figure 1 Astronaut Scott Kelly seated in a simulated Soyuz cockpit

Eyes detect light that has been reflected or emitted from an object. Receptors in the retina send impulses to the brain, which then interprets these electrical signals as ‘vision’.

Different receptors in the eye respond to different wavelengths and intensities of light.

It is possible to misinterpret visual signals both by unusual patterns of light entering the eye, and by the brain making incorrect links (optical illusions).

Figure 1 The Cerebral Cortex is largely devoted to vision in humans.

© NASA /Bill Ingalls

Into space with the BBC micro:bit | a resource for science teachers STEM Learning operates the National STEM Learning Centre and Network www.stem.org.uk

Visual perception

Lesson activityLearning intentions

Resources

Preparation

When the procedure is first run on the Micro:bit device, two vertical blocks of ten LEDs are illuminated.

At random time intervals one of the LEDs in one of the blocks will change intensity. The user must press the A or B button to indicate which block changed within a time limit of two seconds. The display will give feedback on whether the correct button was pressed.

In pairs, students should use the device to assess which person has the better visual perception.

Discuss with the class whether the procedure was an effective test of visual perception. Make adjustments to the procedure if required.

In pairs plan how the device could be used over a period of time to assess if someone’s visual perception was deteriorating.

In pairs identify three tasks or activities that demand good visual perception. Share this list with the class refine it so that there is agreement on the top three tasks or activities that need excellent visual perception.

Show that some individuals have better visual perception than others.Assess whether a simple programmable device can give an effective estimate of visual perception. Link visual perception to the ability to carry out tasks requiring good visual discrimination.

By adjusting inputs in the code which will be highlighted using ‘comments’, students will be able to change the brightness of the LEDs in the Micro:bit display, and so adjust the precision of the test.

• Micro:bit and connecting lead to computer

• Battery pack

• Computer with access to Micro:bit web site to download code

The code for this activity is available here

Once the code has been downloaded it needs to be compiled and flashed to the Micro:bit. Additional help is available here

To start the procedure, press the reset button on the rear of the device.

Into space with the BBC micro:bit | a resource for science teachers STEM Learning operates the National STEM Learning Centre and Network www.stem.org.uk

Visual perception

Assessment opportunities

Taking it further

Ask each group to justify their plan for finding out who had the better visual perception. They should be aware of the importance of an adequate sample size (number of tests) and methods for analyzing their data.

Assess the contributions to the discussion evaluating the effectiveness of the device in assessing visual perception. Do students use evidence to support their claims? Do they listen to the contributions of others and offer helpful feedback?

How effectively can students link their classroom activities to the wider picture and identify careers or activities that demand high standards of visual perception?

Find out some of the reasons why extended periods in space could cause long term problems with visual perception.

Links

Teacher support on Micro:bit site

NASA site describing visual perception problems associated with space flight

Space magazine article on the extent of visual problems experienced by astronauts

Interactive BBC site looking at different aspects of visual perception

Into space with the BBC micro:bit | a resource for science teachers STEM Learning operates the National STEM Learning Centre and Network www.stem.org.uk