E2 Perception of Stimuli

Essential Biology: E2 Perception of Stimuli



Collection of animations from North Harris College

Eye structure tutorial from Sumanas

Eye structure from FreezeRay

Neat virtual eye dissection from eschoolonline

Simple how-the-eye-works from BiologyMad


Explaining Visual Processing


Eight ways to restore sight to the blind, from Discover Galleries

Test your colour vision acuity, from X-Rite

And how does colour vision work? from PhET

AMAZING! Retina implant restores vision. Here’s the article and here’s a patient describing his experience:

How many megapixels is the human eye? from Brainiac.


Try this:

Close your left eye and stare at the +. Move your head closer to the screen and keep staring at the +, but pay attention to the dot. What happens? Explain why.

Explain it yourself first, then check at Serendip’s great website.

The solution and loads more perception demonstrations can be found at Serendip’s playground.

Here is a collection of really simple illusions (including the Hermann Grid) from Richard Wiseman at Quirkology. A nice link to E2 Perception of Stimuli and TOK. Can we really trust our senses?

Here’s another demonstration, via Richard Wiseman’s illusions blog:

Blind Spot illusion. Close your left eye, focus on the small dot. Do you see the large dot disappear?

Blind Spot illusion. Close your left eye, focus on the small dot. Do you see the large dot disappear? From Richard Wiseman’s blog.

Eye defects animation (short vs long sightedness) from FreezeRay.com

Visual Field Explanations, from XKCD.com


Hearing Loss


How the Ear Works, from NobelPrize.org

Ear structures from FreezeRay

The Sense of Hearing from Wisconsin Online

Neat Ear Tutorial from University of Alaska Fairbanks

McGraw Hill Effect of Sound Waves on Cochlear Structures

How sound works, PhET Lab simulation

Test your hearing range (carefully) from the University of New South Wales

How do some blind humans use echolocation to get around?

Can violinists tell the difference between a new, expertly-made violin and a classic Stradivarius? This article by Ed Yong outlines a neat experiment which is a good example of double-blind testing as used in medicine.


Mantis Shrimp: Awesome Vision

Interesting reading:

The peer-iodic table of illusions, from NewScientist.com

The Mantis Shrimp’s amazing visual capabilities, from NotExactlyRocketScience. Is the Mantis Shrimp the coolest animal ever? If you watch this TED Talk on measuring the fastest animals on Earth, you will agree.


TOK: Perception and the (un)reliability of eyewitness testimonies

With the forensic developments of DNA profiling and analysis, we see a move to more reliance on empirical scientific evidence in criminal cases. In recent news stories, many convictions based on eyewitness testimony have been overturned by new DNA evidence. Why are eyewitness testimonies so notoriously unreliable?

This playlist from 60 minutes, “Eyewitness”, looks into some of the issues:

The Innocence Project outlines some of the reasons why eyewitnesses get it wrong.

TruthInJustice outlines some overturned cases, and this academic paper from Durham University outlines the UK’s first exoneration due to DNA evidence – which shows a whole range of forensic evidence in use.

Does taking a photographs impact your memory? 

This article on The Guardian looks at a paper on the effect of taking photos on the photographers’ memories of the objects, with some interesting caveats/ prompts for discussion.


The eye is not irreducably complex – it is the product of natural selection

Evolution of vertebrate eyes from Pharyngula

Owl monkey example of eye evolution, from NotExactlyRocketScience


Inspirational Talk from TED2010

Here is Pawan Sinha talking about how the brain learns to see, and how we can help the children who are born blind in India. Find out more about Sinha’s work and Project Prakash at his university website (MIT).

Amazing reading: Vision chip restores sight to man, Guardian Science

And another talk (by Beau Lotto) on how we see, using some really cool optical illusions:


This BBC clip has some super slo-mo action (and a mantis shrimp starring role), which really highlights how much we miss as we take in visual stimuli:

How do other animals perceive nature? Interactive sliders from Nautilus magazine.

How do other animals perceive nature? Interactive sliders from Nautilus magazine.


Optical Illusions:

Gravity-defying ramp wins illusion contest, from Nature

Illusion contest, from NeuralCorrelate

The ‘blue’ and ‘green’ are the same colour!

Spiral Illusion from Bad Astronomy

In this article from NotExactlyRocketScience, Ed Yong explains that the size of your brain’s visual cortex (which is incredibly variable between people), affects how you see the world – including how likely you are to fall for optical illusions.

The Ebbinghuas illusion – which orange dot is larger? From NotExactlyRocketScience

This one is the Thatcher Effect Illusion. Is Angeline more beautiful this way or upside down?

Thatcher Effect Angelina Jolie, via Quirkology

Thatcher Effect Angelina Jolie, via Quirkology

The next two are after-image illusions:

2008 Illusion of the Year by Lier and Vergeer @Neuralcorrelate. Click to go there.

2008 Illusion of the Year by Lier and Vergeer @Neuralcorrelate. Stare at the dot and see what happens to the colour of the shapes when they turn white. Click on the image to go to the competition finalists website and then settle in for a few hours.


Key terms: stimulus, perception, retina, contra-lateral, edge enhancement, rod, cone, cortex

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