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Solitaire illusion

Exploring the solitaire illusion will help you uncover perceptual differences in terms of either global or local perception.
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Still on the topic of visual illusion studies, let’s move on to the next illusion, the Solitaire illusion. To introduce this, we’d need a bit of your help. In the next couple of slides, you will see some black and white dots. Can you figure out which dots are more? The black ones or the white ones? Are you ready? First slide. Black or white? Black, of course. What about this one? In this one, we have more white dots. And here? Back to black. And in this one? For this slide, most would say black, but actually, there are
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the same number of items: 16 black and 16 white dots. This is a numerosity illusion called the Solitaire illusion because of a pattern that resembles the solitaire game. It seems that items forming a better, clearer configuration are overestimated. In this case, black dots form a single Gestalt, a single configuration, and are overestimated compared to white dots that are formed as separate clusters. How can we investigate such a complex numerosità illusion with a free choice test? Again, food could be the answer. Imagine having a highly preferred food, one that has a particular color and a non-preferred food with a different one. You may arrange preferred and non-preferred food like white and black dots in a way to reproduce the solitaire illusion.
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This is exactly what was done in a research study in Atlanta in 2014. It’s known that chimps love M&M’s, but they don’t really like cereals. So for the experiment, blue M&Ms were used as the preferred food, and yellow cereals were used as the non-preferred food. So if you present chimpanzees with two groups of M&Ms differing in number, they would want to reach the larger group of M&M’s, regardless of the number of cereals present in the group. Then in the test phase, two illusory patterns were presented. In one array, blue M&Ms were centrally located with yellow cereals in the periphery, while in the other, M&Ms were in the periphery. But it’s always 16 M&Ms versus 16 cereals and vice versa.
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It was found that chimps really want to maximize the number of M&M’s when there is a true numerical difference between the two groups. Instead, in the presence of the illusion, they go randomly. They did not choose one group over the other. So, no evidence of solitarie illusion was perceived in this species. This is an example of how a free choice test is used to investigate the solitaire illusion. What about integrating an alternative methodological approach, the training procedure? How is this done? How can we train animals to respond to a numerical task? Well, we can ask apes and monkeys to select the array containing more black dots by touching a screen.
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If they want to obtain a food reward, like a pellet, they have to tap the screen to choose the array with more black dots. Then we presented the illusory patterns. In one array, black dots were centrally located. And in the other, they were located in the perimeter. And see whether they showed any perceptual bias. Indeed, if they believe that one array contained more black dots, we would have expected a choice for this array. But also, in this training procedure, we did not find evidence of solitaire illusion in monkeys. So could this just be a human prerogative? Interestingly, such perception has been found in
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a more distantly related species: guppies. So this was the experimental apparatus
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which was divided into three areas: their home compartment, the starting box, which was the starting point of each trial, and the experimental area, where the stimuli was presented. Fish were shown two groups made up of white and black dots. They were trained to select the array containing the larger number of black dots in order to get food, such as this one. In the presence of the illusion guppies selected the array with black dots centrally located, demonstrating perception of the solitaire illusion. Therefore, we can conclude that some perceptual mechanisms underlying numerical estimation are similar between humans and fish. So what does it mean when an animal sees the Solitaire illusion?
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Well, we know that when we see stimuli, we could have either a global or a local perception. Global precedence is when you first notice the global or bigger picture before the finer details. In this example, if you have global precedence, you will first notice the letter E. On the other hand, if you have local precedence like pigeons, you will notice one of the small letters A. So which did you notice first? I’m sure it was letter E, as humans have global precedence, where we see the forest before the trees. And this also applies to animals. The solitaire illusion is based on the perception of a big single configuration starting from smaller stimuli.
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We perceive the big cross to have the numerosity illusion. Therefore, the fact that guppies are susceptible to solitaire illusions suggests that like humans, they may also perceive the forest before the trees.

Now that we’ve taken a look at the Delboeuf illusion, let’s move on to the second one in the series: the solitaire illusion.

Exploring the solitaire illusion will help you uncover perceptual differences in terms of either global or local perception. Find out more in the video.

If you have any questions, insights, or realisations, feel free to share them in the Comments section.
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Research Methods in Psychology: Using Animal Models to Understand Human Behaviour

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