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Mental Images

Mental Images. The visual system encodes patterns of light and their inter-relationships Images in the visual system are partly created by these patterns of light on the retina. However, the image on the retina, is two-dimensional, upside down, and mostly out of focus.

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Mental Images

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  1. Mental Images • The visual system encodes patterns of light and their inter-relationships • Images in the visual system are partly created by these patterns of light on the retina. • However, the image on the retina, is two-dimensional, upside down, and mostly out of focus. HKU

  2. Top-Down Processing in the Visual System • The three-dimensional, right-side up, clear image that we see is created by our brain. • Is it possible that cognitive processes such as problem-solving can use this access to the visual system even when there isn’t stimulation on the retina? HKU

  3. Scanning Mental Images • Kosslyn, Ball, and Reiser (1978) had subjects memorize picture of island. • Asked them to focus on one location of their mental image, and then asked them to (mentally) go to another location on the image. • The time to get to the new location was proportional to the distance on the actual picture. HKU

  4. Mental Rotation • The time required to mentally rotate objects in space (in order to recognize them) is linearly related to how much they need to be rotated to be in a familiar position Shepard, 1968 Cooper, 1975 HKU

  5. Concepts and Categories • Is the world naturally divided into categories or are the categories we perceive a consequence of how our minds see the world? (Philosophy) • Theories of concepts have changed significantly over the past 30 years. HKU

  6. From Definitions to Theories • For centuries, concepts were seen as sets of necessary and sufficient features that define categories. • Rosch (1975) changed this view by presenting evidence that concepts are more probabilistic. HKU

  7. Prototypes and Family Resemblance • Concepts are collections of features that are neither necessary nor sufficient. • When we learn category concepts, we compare sets of features: if most features are similar and few are dissimilar, then we group thing together --> family resemblance HKU

  8. Concepts as collections of prototypical features • From observing numerous examples of particular categories, we form prototypes --> non-existent category representatives that embody all of the most common features. HKU

  9. The Basic Level • Prototypes and family resemblance are strongest at what Rosch termed the basic level --> bird vegetable game car HKU

  10. Empirical Evidence for the Basic Level • Subjects are asked to rate properties of different instances of categories (e.g., how important is having two legs to being a bird?) • These ratings are then used to compute family resemblance scores for different types of birds. • Subjects typicality ratings are correlated with FR scores. HKU

  11. Summary • The basic-level cuts the world up into categories that have the most family resemblance. e.g., furniture mammal chair dog car seat poodle HKU

  12. Picking Out the Right Features • Why don’t we compare objects in terms of volume, time in a specific location, distance from home, etc. --> infinite number of features • How do we choose the right ones? HKU

  13. Concepts as Theories • Concepts are more than just collections of probabilistically inter-related features. • They are held together by a theoretical /explanatory glue. HKU

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