Lecture 2.1 What is Perception?

Transcription

1 Lecture 2.1 What is Perception?

2 A Central Ideas in Perception: Perception is more than the sum of sensory inputs. It involves active bottom-up and topdown processing. Perception is not a veridical representation of the real world.

3 Learning Outcomes Knowledge: list and describe three paradigms for studying perception. Value: adopt an appreciation for the differing theoretical paradigms.

4 Quick Overview 1. What is perception? How does it differ from sensation? 2. How does it differ from cognition? 3. Paradigms to investigate perception Image (cc) provided courtesy of brain farts

5 1. What is Perception??? And how does it differ from sensation? Image (cc) provided courtesy of readerwalker

6 1. What is Perception??? And how does it differ from sensation? Sensation: The reception of energy from the environment, and its initial encoding into the nervous system. Perception: The process of interpreting and understanding sensory information.

7 Types of Perceptual Processing Perceptual Processing relies on a combination of: Data Driven (bottom-up) Processing is driven by the stimulus. Conceptually Driven (top-down) Processing is driven by higher level knowledge.

8 Is our perception veridical? (Is perception a true and accurate reflection of our physical world?) Quite often we perceive things that do not exist and misperceive or even fail to perceive things that do exist. Perception does not provide a veridical treatment of our physical world. That is, we may be ignorant of specific environmental features OR we may construct features that are missing.

9 Simons and Levin (1998)

10 Perception uses previous knowledge to gather and interpret stimuli registered by the senses. (Matlin, 2009, p 33) Key features: active data-driven conceptually-driven

11 2. How does perception and cognition differ? Artificial distinction because information reception and processing is continuous.

12 Commonalities between perception and cognition (Tacca, 2011) Do visual representations share similar properties with cognition? Semantic systematicity: the ability to construct correct representations of the meaning of novel stimuli. The model of visual feature binding displays systematicity similar visual scenes have primitive features that are spatially arranged in different combinations.

13 Perception and cognition artificial distinction because information reception and processing is continuous. Why do scientists, and all humans, like to establish clear category boundaries?

14 3. Paradigms to investigate perception Paradigm a set of assumptions, concepts, values or practices that constitutes a way of viewing an issue. Classic information processing approach Connectionist approach Ecological approach

15 Brief Explanations Information Processing Approach Sensory information is analyzed in a series of stages (e.g., components whole) Connectionist Approach Levels of information (e.g., features, letters, words) are highly interconnected. Ecological Approach Perception is a result of the nature of the environment.

16 Summary Perception involves processing sensory information to the level of meaning or understanding. The distinction between perception and cognition is artificial. There are several paradigms to investigate perception.

17 Lecture 2.2 Perceptual Paradigms

18 It involves active bottom-up and topdown processing. There is a debate regarding the degree to which we add or distort information in the proximal stimulus.

19 Learning Outcomes Knowledge: explain three paradigms for studying perception, and explain the differences between constructivist and direct perception.

20 Quick Overview 1. Information Processing Bottom-up and Top-down 2. Connectionist 3. Ecological Image (cc) provided courtesy of brain farts

21 1. Information Processing Approach Sensory information is analyzed in a series of stages (e.g., components whole) Bottom-up processing: start with small bits of sensory information, which are then combined to for a percept.

22 Theories Template matching theory: every stimulus is compared to a previously stored pattern (or template). Feature analysis theory: perception is the result of detecting patterns on the basis of a collection of individual features.

23 Feature Analysis Theories Letters/Words Pandamonium Features: lines, curves, angles Letters: combination of features Words: combination of letters Objects Recognition by Components Features: geons basic geometric shapes Object recognition **Note feature analysis and RBC differ in they emphasize different structural analyses.**

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26 1.1 Bottom-up and Top-Down Data Driven (bottom-up): processing is driven by the stimulus. Issue: context effects. Conceptually Driven (top-down): processing is driven by higher level knowledge.

27 Examples of Top-Down Processing

28 2. Connectionist Approach Neurally inspired models of cognition. Figure 1.2 in McLeod, Plunkett, and Rolls (1998)

29 Connection Models 1. Layers: Input Units, Hidden Units, Output Units 2. Connection strength is modifiable 3. Connections within a layer are inhibitory; connections between layers are excitatory.

30 INPUT UNITS HIDDEN UNITS OUTPUT UNITS

31 McClelland and Rumelhart (1981)

32 Information Processing and Connectionist Approaches Both assume that the perceiver acts upon the proximal stimulus (image on the retina). Information is added Constructivist approach to perception.

33 3. Ecological Approach JJ Gibson Perception involves the direct absorption of information present in the environment. We do not add information to the stimulus.

34 Key Point Gibson argued that perception was a result of stimulation. No need to create internal mental representations. People do not just perceive objects, they also perceive affordances.

35 Summary Perception, like cognition, can be viewed from many perspectives. The differing perspectives have all added to our understanding of perception. Today, cognitive psychologists are developing theories that integrate two or more of these perspectives.