Crash Course Psychology #7 is where I learn all about our sense of Perception and how it’s easily influenced.
For context, Crash Course inspired me to learn the basics of psychology, so I’ve made it my mission to watch the entire Crash Course Psychology playlist and paraphrase each episode in my own words. This journey wouldn’t have been possible without the Crash Course team, so many thanks to them! To showcase what I learnt, here is my personal paraphrase of episode 7:
Perception
Previously, we’ve defined perception as the top-down way our brains organise and interpret outside stimuli and put it into context. Our minds are constantly receiving so much of that outside stimuli, especially through the eyes, and the mind has to make quick work of it. Also, our minds do all the work of perceiving, while our eyes and other senses are only feeding it raw data from those those outside stimuli. It’s important raw data, but it’s not what we actually see. What we see happens in the mind. Our senses mean little without our brain’s ability to organise and translate all that data into meaningful perceptions.
Perceptual Set
What heavily influences our perception, sometimes causing bias, are a myriad of things. Examples include our expectations, experiences, moods, and cultural norms. Things like context, cues received, familiarity, emotions, motivations, all can affect our perception, causing different interpretations to the same stimuli. All these fall under our Perceptual Set, the psychological factors that determine how you perceive your environment. Perceptual Set theory teaches us that what we believe makes us see what we want to see. Most of the time our perceptual set reaches reasonable conclusions, but sometimes they can mislead or even harm us. It’s the basis for many optical illusions.
Form Perception
Our mind has many ways to perceive all that outside stimuli into something coherent. Below are some of the ways our brain tries to do that.
Figure-Ground Relationship
The organisation of the visual field into objects (the figures) that stand out from their surroundings (the ground). We essentially organise what we see into two main parts: the canvas and the main focus on that canvas. This applies to non visual fields too, such as listening on a particular sound becomes the figure, while all the other noise becomes the ground. Now that the mind has distinguished the two, it has to perceive something meaningful from them.
Rules of Grouping
Another way our minds shuffle all the stimuli it receives. It follows rules of grouping, like organising things by;
- Proximity
- States that we like to group nearby figures together. So as opposed to seeing a bunch of nearby things as separate, we tend to mentally lump and connect them together.
- Continuity
- We perceive smooth continuous patterns rather than discontinuous ones. We tend to give attention to continuity, and often ignore the broken ones.
- Closure
- Visually, we want to fill in gaps to create whole objects. We tend to see things that aren’t there just to fill in those gaps so we can see a full image.
Depth Perception
Depth Perception is the ability to see objects in three dimensions although images that strike the retina are two-dimensional. So even though our eyes receive light waves that get focused into 2D images for our retina, our depth perception allows us to see in 3D somehow.
Depth Perception helps us estimates an object’s distance and full shape. It is at least partially innate, since babies have it too. We’re able to perceive depth using both binocular and monocular visual cues;
Binocular cues
Depth cues, such as retinal disparity, that depend on the use of two eyes. Basically we need both eyes to catch these depth cues.
- Retinal Disparity
- A binocular cue for perceiving depth. Because our eyes are around 2.5 inches apart, our retinas receive slightly different images. So when we look with both eyes, our brain compares the two images to help judge distance. So when you look at an object and the closer it is, there is greater difference between the two images from your 2 different retinas. This is Retinal Disparity. Since the differences between images vary only slightly, it is most useful when judging distance near, but doesn’t help much when judging far distances. For that, we use Monocular cues.
Monocular cues
Depth cues, available to either eye alone. Helps to determine the scale and distance of an object. The cues are;
- Relative Size & Height
- Being able to judge distance by inferring to sizes and heights of objects in relation to each other.
- Linear Perspective
- Parallel lines when going into the distance can seem like they will meet. The closer the lines together, the greater the distance it seems.
- Texture Gradient
- The closer things are to us, the more finely textured and detailed it is. The further something is, the less detail we see.
- Interposition
- Overlap cue. Tells us when some things are in front of or behind another. When something blocks the view of another, we perceive that something as closer.
Motion Perception
We use motion perception to infer speed and direction of a moving object. Our brain gauges motion based partly on the idea that objects that look like they are shrinking are retreating, while objects that look like they are enlarging are approaching. This helps generally, but out brains can easily be tricked. For instance, large objects appear to move much more slowly than small ones going at the same speed.
Perceptual Constancy
In addition to organising what we see based on things by form, depth, and motion, our perception of the world also needs consistency. We call this constancy in Psychology. Perceptual Constancy is what allows us to continue to recognise an object regardless of viewing distance, viewing angle, the object’s motion or illumination. Even changes to its colour, size, shape, and brightness, depending on the conditions, we can still recognise the object.
Conclusion of Crash Course Psychology #7
In the end, your perception is about how you understand the world and your place in it, both physically and psychologically. Your sensory organs (eyes, nose, etc) pull in raw data from the world when in contact with stimuli. That raw data gets disassembled into bits of information and then reassembled in your brain to form your own model of the world. Your brain constructs your perceptions.
Watch Crash Course Psychology #7 to see cool demonstrations of all the above!
Danniel’s thoughts on Crash Course Psychology #7
- If our minds can be so easily deceived (at least visually), I wonder if the same can be accomplished with our other senses. Like, can we receive stimuli of something but interpret that stimuli entirely differently? Depending on the interpretation I presume, would that interpretation be considered “wrong” or simply “different”? I’m curious, so many possibilities!
Enjoyed this learning of Psychology? Test your knowledge against these quick custom Kahoot! quizzes I’ve made based on the episode above: This is the easy mode and this is the hard mode for Crash Course Psychology #7.
Also, do check out what else Psychology related I’ve learnt from my Psychology blog!
Credits for Crash Course Psychology #7
Original Content & Media by Crash Course
Content Consumed and Paraphrased by Danniel Iskandar
Paraphrase Proofread by
Paraphrase Reviewed by