Astronaut's Dilemma & More!

GESTALT: an organized whole

Gestalt Principles to group Stimuli and to form Perception...

• proximity: group nearby things together
• similarity: group similar figures together
• continuity: perceive smooth, continuous patterns instead of choppy, discontinuous patterns
• connectedness: group things that are uniform and linked
• closure: we fill in gaps to create a complete whole figure/object
• figure-ground: organization of the visual field into objects (figures) that stand out from their surroundings (ground)

Depth Perception: seeing objects in 3 dimensions and the ability to judge distance

Retinal disparity, a binocular cue, allows us to perceive depth and provides us with the ability to determine the relative distance of different objects. Retinal disparity while looking straight and far ahead is not very effective in judging distance, so we use monocular cues.

Motion Perception



Brains perceive motion as a rapid series of slightly varying images, a phenomenon known as stroboscopic movement.

Brain Processing:

• bottom-up: analysis which begins with sensory receptors and works up to the brain's integration of sensory information
• top-down: analysis guided by high-level mental processes, such as when perception construction or drawing on experiences/expectations; progression from a whole to its elements

When people see optical illusions, they first use top-down processing. So, they see the whole picture (instead of its several elements) and try to make sense of it, but it doesn't work. This is because optical illusions trick different parts of perception, such as depth perception and contours. Since top-down processing is guided by perception construction, top-down processing makes people very vulnerable to illusions.

Astronauts Dilemma:

     Top-down processing will be tricky but important for the astronauts. During top-down processing, the brain focuses on the whole first, and then works its way down to analyze the various details of the whole. This processing allows the brain to form perceptions. Top-down processing can be important for the astronauts, so they should be sharpening their depth and motion perception skills. These skills could be useful to an extent, considering depth and motion could be vastly different under conditions on different planets. Therefore, their perceptions would also be different. Top-down processing can harm the astronauts by making them vulnerable illusions too. If their perceptions are different than reality, due to illusions, their data could be affected by their perceptions. So, the astronauts should be wary of perceptions and need to focus on details first, using bottom-up processing.
     Possibly the most important Gestalt strategy is determining figure-ground relationships. Knowing how objects are organized in comparison to their surroundings will be really important for the astronauts to travel through the different planets. Also, the principles for grouping could be useful, but they also may be harmful if perceptions made by top-down processing are fooled by illusions. Grouping stimuli based on perceptions is tricky business, considering the human brain is always trying to create order out of patterns, even when there aren't any. So, the astronauts should be wary of Gestalt strategies for perceiving objects and patterns, because top-down processing can taint reality. However, they should focus on perceiving accurate figure-ground relationships.
     The astronauts should look for binocular and monocular cues to help with figure-ground segregation by forming depth perceptions. Binocular cues, such as retinal disparity, will help the astronauts determine the relative difference between objects. However, if objects are straight ahead, retinal disparity won't be very useful, so they should search for monocular cues, such as relative size, interposition, and light/shadowing. Relative size will help the astronauts perceive which objects are closest and which are farthest. Interposition allows the astronauts to determine how the objects are layered upon each other. Also, a brighter image is perceived as being close, while dimmer images are perceived as being far away. All of these cues will help the astronauts determine which objects are the figures, and which objects are the ground. So, they should look for these cues, while always being wary of illusions.

*more information about binocular and monocular cues can be found in the blog post "The Laws of Perception"