Textbook Notes (368,125)
Canada (161,663)
Psychology (1,468)
PSYCH 1XX3 (384)
Chapter 4

Ch. 4 notes - Form Perception.doc

6 Pages
Unlock Document

Christopher Teeter

Form Perception Gestalt Principles of Grouping • Gestalt Psychology – a theory to account for how we perceive the environment • “gestalt” = the way something is put together/configured (German) • Often report seeing more than just the sensory info that falls on our retina – visual system puts info together to make it easier to interpret – attempt to organize info into simple groups • “the whole is greater than the sum of its parts” • Ex. a group of 10 dots in a row is reported as a ‘line of dots’ instead of saying ’10 dots’ • Law of Pragnanz – we have a bias to organize things into the simplest organization • Ex. a group of 10 dots in a row is reported as a ‘line of dots’ instead of saying ‘dot’ 10x 6 Principles of Gestalt organization: 1. Figure-ground: When perceiving a visual scene, we organize the info as the central object of identification (figure), while the other objects fade into the background (ground) – object will be perceived as separate from its background 2. Proximity: things that are closer together will be perceived as members of the same group • Ex. 9 little squares spread out is just 9 squares but when they are all right beside each other (form 1 big square), we perceive them as 1 group 3. Closure: our brains not only process info from the visual scene, they actively interpret it – when we see an incomplete object, we fill in the gaps • Ex. WWF panda symbol is incomplete but we still see it as a panda 4. Similarity: things that share visual characteristics (ex. shape, size, colour, texture, value, orientation) will be seen as belonging together • Ex. squares form a plus sign in a grid of circles ad squares 5. Continuity: points that are connected by straight/curvy lines are seen in a way that follows the smoothest path – rather than seeing separate lines and angles, lines are seen as belonging together • Ex. 4 lines of dots are seen as forming an X pattern together 6. Common fate: elements tend to be perceived as grouped together if they move together • Ex. if you were walking through a park and there was a green snake lying in the grass, you probably wouldn’t notice it – as soon as the snake moves, you would notice it immediately – its movement causes your visual system to organize the figure against the background Role of Expectation in Perception of Patterns and Objects • When our interpretation emerges from the data (image that falls on retina), this is known a s data-driven/bottom-up processing • When our perception is influenced by sources beyond images in the retina (ex. knowledge/experience), higher-level cognitive processing is engaged to interpret the image; this is known as prediction /top-down processing • Influence of top-down processing has been shown through rat/man stimulus – subjects viewed this image after looking at pictures of animals/faces – depending on what they saw previously, they reported seeing a rat/man wearing glasses – they had been primed for one or the other interpretation of an ambiguous picture by being shown the previous slides – this is a form of top-down processing – expectations influence what we perceive Theories of Object Recognition in Humans • Studies focused on 2 questions: how are objects represented in the brain? and how do we match unlimited combinations of possible viewing conditions with our representation of each object? • Any complete theory must explain how humans are able to reliably identify specific objects from an unlimited number of orientations • Recognition-by-Components (RBC) – accounts for the successful identification of objects despite changes in the sixe/orientation of the image – also explains how moderately occluded/degraded images as well as novel ex. of objects are successfully recognized by the visual system • based on the assumption that just about any objects can be represented as an arrangement of 3 dimensional shapes (ex. cube, cylinder, cones, etc.) called geons • geons are a part of the object ‘alphabet’ and unique combinations from the equivalent of object ‘words’ that can be readily interpreted by the visual system • as we view an object, our visual system segments different geons and their relationship to one another • recognizing a geon involves recognizing the features that define it (feature analysis) • having identified the pieces out of which the object is composed and their configuration, one recognizes the objects the pattern composed from these pieces (a prototype comparison) • strength: people can typically recognize about 30,000 objects with the use of only 36 different geons • this model argues that we can see objects from unlimited viewpoints – different views of the same object should still lead to the same set of geon recognition – achieves view invariance • drawbacks: invariant features are difficult to extract in real images (ex. slight variations in lighting can completely change the unique features of a face that are used for individual identification)  geons are also poor at representing many natural objects that may/may not have simple parts-based descriptions (ex. many birds have tapered beaks and could be described by the same geon, but there is a lot of subtle variation in the features of bird beaks) – our knowledge of geons doesn’t help us understand how we distinguish between 2 birds with slightly different features • Template Matching Model – incoming sensory info is compared to copies (templates) stored in long-term memory – stored in the process of our past experiences and learning • Assumes that a retinal image is faithfully transmitted to the brain and that an attempt is made to compare it to a large number of literal copies (templates) in order to find a match against all templates • Works well when exact matches are expected (ex. computers (search for exact sequences of code)/barcode readers), but not with humans
More Less

Related notes for PSYCH 1XX3

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.