Which square is bigger? Honeybees see visual illusions like humans do


File 20171120 18525 1l2j7n8.jpg?ixlib=rb 1.1
Flowers may take advantage of visual illusions to attract bees.
from www.shutterstock.com

Scarlett Howard, RMIT University and Adrian Dyer, RMIT University

When a human looks at a distant skyscraper, it appears small to the eye. It’s a visual illusion, and we use other contextual information to know the building is actually tall.

Our new study shows, for the first time, that honeybees see size-based visual illusions too. Whether a size illusion is seen, or not, depends on how a target object is viewed.

These new results help us understand how visual illusions evolved in different species over time.


Read more: Three visual illusions that reveal the hidden workings of the brain


How humans experience illusions

Humans see lots of different illusions such as mirages, illusions of shape, length, size, and even colour (remember that dress?).

The lines or shapes around an object can change the way your brain sees it.
Provided by Scarlett Howard

Visual illusions are errors in your own perception which can allow you to process the very complex visual information you see more easily.

One of the strongest geometric illusions we humans see is an illusion of size, called the Ebbinghaus Illusion.

Ebbinghaus Illusion: The central circles are of identical size, but are perceived as very different by humans because we use context to inform our vision.
Provided by Scarlett Howard

Interestingly, species such as bottlenose dolphins, bower birds, domestic chicks, and redtail splitfins see this illusion in the same way as humans. However, animals such pigeons, domestic dogs, and bantams see the opposite illusion to what we see, and baboons do not see an illusion at all.

To understand why different species see size illusions in such different ways, and how an insect with a miniature brain might view a size illusion, we developed an experimental design using honeybees.


Read more: Want a better camera? Copy bees and their extra light-sensing eyes


Bees can help us design better camera technology.

Why do animals perceive illusions differently?

It’s intriguing that some species view size illusions the same way as us, and some animals do not. Why is it that a baboon does not see any illusion when looking at the Ebbinghaus Illusion? Why do pigeons and dogs see the opposite illusion to us? Our team decided to look into the methodology of the past studies that had shown these differences.

When baboons, pigeons, dogs, and bantams were tested, they were looking at the illusion from either a set distance or from a forced close-range distance. For example, dogs had to touch the correct option with their noses, and birds had to peck the correct option meaning these species were viewing the illusion at a very close distance. Baboons, on the other hand, were viewing the illusion at a set distance, unable to move closer than a certain distance from a screen that presented the illusionary pictures.

With this knowledge, we decided to test honeybees using two study conditions:

  1. a free-flying set-up where bees could fly at any distance from the size illusion before making decisions, and
  2. a constrained viewing set-up where bees could only view and make decisions about the illusion from one set distance.

How does a bee view size illusions?

To determine if bees could perceive size illusions, we first had to find a way to ask them.

We trained one group of bees to always choose the larger black square on a square white background and another group of bees to always choose the smaller black square on a square white background.

When bees had learnt to either choose larger or smaller sized black square targets, we manipulated the size of the background, thus trying to induce the perception of a visual illusion (similar to the Delboeuf Illusion).

Stimuli used in experiments.
Provided by Scarlett Howard

We ran this experiment using our free-flying, unrestricted viewing condition and also using a restricted viewing condition where independent bees were unable to choose their own distance to make decisions.

Eureka! Training conditions explain why different animals see illusions differently. Bees in the unrestricted viewing condition perceived illusions, while bees in the restricted viewing condition did not see size illusions.

Now, we are interested in whether some past study results were due to experimental set-up: maybe more or even all animals could perceive illusions like humans, depending on the context in which they are viewing these illusions.

What does this mean for the evolution of vision?

Visual illusions are useful because they allow us to process complex scenes, with multiple pieces of information, as a whole by using context as a cue. Since different animals see size illusions, understanding how this works could help us learn more about how vision itself evolved.

One explanation of why such different animal species, from humans to bees, see size illusions is because an ancient ancestor had this ability, and it has been conserved throughout evolution. However, a more likely scenario is that the evolution of visual illusion perception is due to convergent evolution. This occurs when different species evolved the ability to perceive illusions separately.

The ability of bees to perceive a size illusion in a free-flying environment also has implications for flower evolution. Flowers could have evolved to exploit the ability of bees seeing illusions to make nectar areas look more appealing. One genus of flower, Wurmbea, appears to have illusionary properties such as differently sized flowers with patterns reminiscent of size illusions such as the Ebbinghaus and Delboeuf Illusions.

Wurmbea flower as seen through a special camera simulating bee vision.
http://ro.uow.edu.au/asj/vol5/iss1/7

The ConversationA very important lesson from this study is that viewing context can make scenes appear very different to reality. This is very important to remember when working on vision in humans or any other animal.

Scarlett Howard, PhD candidate, RMIT University and Adrian Dyer, Associate Professor , RMIT University

This article was originally published on The Conversation. Read the original article.

Bee aware, but not alarmed: here’s what you need to know about honey bee stings



File 20171116 11028 z8x2g2.jpg?ixlib=rb 1.1
Bees don’t attack unless they feel threatened.
Shutterstock

Ronelle Welton, University of Melbourne and Kymble Spriggs, University of Melbourne

A Victorian man died yesterday after being stung by several bees. While bee sting deaths are rare (bees claim around two Australian lives each year), bees cause more hospitalisations than any venomous creature.

Bee stings cause nearly the same number of deaths each year as snake bites.
The University of Melbourne’s Pursuit/Internal Medicine Journal

Around 60% of Australians have been stung by a honey bee; and with a population of more than 20 million, that’s a lot of us who have just experienced pain and some swelling.

So what happens when we’re stung by a bee, and what determines whether we’ll have a severe reaction?


Further reading: Ants, bees and wasps: the venomous Australians with a sting in their tails


How do bees sting?

Honey bees work as collective group that live as a hive. The group protects the queen, who produces new bees, with worker bees flying out to collect nectar or pollen to bring back to the hive.

Bees have a venom sac and a barbed stinger at the end of their abdomen. This apparatus is a defensive mechanism that is used if they feel under attack; to defend the hive from destruction. The barb from a bee sting pierces the skin to inject the venom, with the bee releasing pheromones that can incite other nearby bees to join the defensive attack.

Honey bees work as a collective.
Shutterstock

The venom is a complex mixture of proteins and organic molecules, that when injected into our body can cause pain, local swelling, itching and irritation that may last for hours. The specific activity of some bee venom components have also been used to treat cancer.


Further reading: Curious Kids: Do bees ever accidentally sting other bees?


A single bee sting is almost always limited to these local effects. Some people, however, develop an allergy to some of these venom proteins. Anaphylaxis, a severe allergic reaction that is potentially life-threatening, is the most serious reaction our body’s immune system can launch to defend against the venom.

It is our body’s allergy to the bee venom, rather than the venom itself, that usually causes life-threatening issues and hospitalisation.

How do I know if I am allergic?

If you have not been stung by a bee before you are unlikely to be allergic to the venom. However, if you have been stung by a bee, there is the potential to develop an allergy. We do not know why some people become allergic and others don’t, but how often you are stung seems to play a role.

If you have experienced very large local reactions from a bee sting, or symptoms separate from the sting site (such as swelling, rashes and itchy skin elsewhere, dizziness or difficulty breathing) you may have an allergic sensitivity. Your doctor can assess you by taking a full history of reactions. Skin testing or blood allergy testing can help confirm or exclude potential allergy triggers.

An allergy specialist is key to assess people’s risk of severe allergic reactions (anaphylaxis).

There is an effective treatment for severe honey bee allergies, called immunotherapy. This involves the regular administration of venom extracts with doses gradually increased over a period of three to five years. This aims to desensitise the body’s immune system, essentially to “switch off” the allergic reaction to the venom.

Venom immunotherapy is very effective at preventing severe reactions and is available on the Pharmaceutical Benefit Scheme, whereas other immunotherapy treatments in Australia cost an average of A$1,200 per year.

First aid for a bee sting

Bees usually leave their barbed sting in the skin and then die. Remove the sting as soon as possible (within 30 seconds) to limit the amount of venom injected. Use a hard surface such as the edge of a credit card, car key or fingernail to flick/scratch out the barb.

For a minor reaction such as pain and local swelling, a cold pack may help relieve these symptoms.

If a bee stings you around your neck, or you find it difficult to breathe, or experience any wheezing, dizziness or light-headedness, seek medical advice urgently.

Prevention

Despite being a species introduced by European settlers, the honey bee (Apis mellifera) plays an essential role within Australian agriculture. We need to appreciate their essential functions, and try to prevent stings.


Read more: Losing bees will sting more than just our taste for honey


If you see a bee let it be (sorry); don’t swat it or step on them. Our bees don’t attack unless they feel they need to defend their hive.

Do not attempt to locate a hive, call an expert.

The ConversationFor more information on allergies go to the ASCIA website. Local bee keeping groups are a good source of knowledge about local bee populations.

Ronelle Welton, , University of Melbourne and Kymble Spriggs, Clinical Associate Professor, University of Melbourne

This article was originally published on The Conversation. Read the original article.