Chapter 2 - Perception Part 1 (Start - Perception & Action) Flashcards
What is the difference between perception and sensation?
Sensation refers to a PASSIVE process of bringing information from the outside world into the body and to the brain.
Perception is an ACTIVE process. Refers to the ACTIVE organization and interpretation of sensory information into something meaningful.
What are the 2 different types of theories we use to recognise patterns?
Templates and Features.
According to the template theory, what is a template?
Forms or patterns stored in long-term memory corresponding to each of the visual patterns we know.
Pattern is recognized when its template is matched to the stimulus input. -> provides closest match
List some pros and cons of using the template theory to recognise patterns.
Pros:
- Common-sense; a rather intuitive method
Cons:
- Matching will fail even with minor differences between the template and the input.
- Ill-equipped to account for the flexibility shown by people when recognizing alphabetical and numerical symbols –> becomes obvious when the stimulus belongs to an ill-defined category where no single template will suffice (eg building)
What are some assumptions you can make to improve template theories?
1) Assume that the visual stimulus undergoes a normalization process.
2) Assume that there is more than one template for each letter and digit.
How does the assumption that visual stimulus undergoes normalization help in pattern recognition?
Helps you to produce an internal representation of the visual stimulus in a standard position.
Makes you search for a matching template.
However, by assuming that visual stimulus undergoes normalization, are there any things you might be discounting?
You overlook the possibility that your visual stimulus might not always be consistent with your template.
Not possible for whatever stimulus you experience to always be consistent with your template.
With this (cannot assume normalization) being said, what other assumption should you make to make template theories more effective?
Should assume that there is more than one template for each letter and digit.
What are the advantages of assuming that there is more than one template for each letter and digit?
Permits accurate matching of stimulus and templates across a wider range of stimuli
Does considering the fact that each digit and letter has more than one template makes the template theory more complicated?
Yes.
What assumption is held by most feature theorists?
Pattern recognition first involves specific processing and is then followed by more global or general processing to integrate information from the features.
How did Navon prove that global processing CAN precede more specific processing?
Presented observers with stimuli (a big S formed with small S or small H or big H formed with small H and small S) - 4 conditions.
Found that performance speed with the small letters was greatly slowed when the large letter differed from the small letters. In contrast, decision speed with the large letter was not influenced by the nature of the small latter. In this case, we often see the forest/global structure/big letter before the tree/specific structure/small letter.
What did Neisser do that helped to lend support to the feature theory?
2 lists of non-words with a common target letter Z. For the first list, Z is beside unrounded alphabets that consisted of straight lines like Z itself, whereas in the second list, Z is beside unrounded alphabets.
Compared time taken to detect letter Z. Performance was faster in the latter condition because the distractors shared fewer features with target letter Z.
What types of cells did Hubel and Wiesel study?
Cells in parts of the occipital cortex (at the back of the brain) associated with the early stages of visual processing.
What did Hubel and Wiesel observe?
Some cells responded in 2 different ways to a spot of light depending on which part of the cell was affected.
- An “on” response with an increased rate of firing when the light was on.
- An “off” response with the light causing a decreased rate of firing.
What did Hubel and Wiesel discover?
There are 2 types of neurons in the primary visual cortex: Simple cells and complex cells.
What are the traits possessed by simple cells?
- Have “on” and “off” regions with each region being rectangular in shape.
- These stimuli respond most to dark bars in a light field, light bars in a dark field, or straight edges between areas of light and dark.
- Any given simple cell only responds strongly to stimuli in a particular orientation
Responses of these cells could be useful and relevant to feature detection.
What are the traits possessed by complex cells?
- Responds to moving contours
- We have more of these than simple cells.
The responsiveness of end-stopped cells depends on __________ and ___________.
stimulus length, orientation.
Pattern recognition involves both top-down processes and bottom-up processes. True or false?
True.
Use the word superiority effect to explain how pattern recognition involves top-down processes.
WSE: The finding that a target letter is detected faster when presented in words than in non-words. Suggests that information about the word presented can facilitate identification of its letters.
Top-down: Information about the word presented can facilitate identification of the letters.
What is the pseudoword superiority effect?
Letters are easier to identify when presented in pseudowords than in nonwords.
What patterns do you observe in medical diagnosis when it comes to pattern recognition?
Experts are more likely than non-experts to use implicit reasoning, whereas the non-experts made more use of analytic reasoning. However, other evidence indicates that medical experts often start with fast, automatic processes but cross-check their diagnoses with analytic ones.
Explain interactive activation model and top-down activation.
Negative example: If it’s a non-word, there’s no top-down effect, and hence words won’t be activated first before letters are activated.