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Describe Treisman’s Singleton Search Paradigm.
present a display that consists of items where the participant is tasked with looking for one target
the target can be either present or absent
if the target is absent, the search will take longer, since the participant has to search exhaustively
there can be a pop-out stimulus or conjuction stimulus — parallel vs. serial
What signature in the data allowed Treisman to distinguish between a serial and parallel search? Make a diagram of the results for both target absent and target present trials.
data shows set size on x-axis and reaction time on y-axis — does increasing the number of things to look at take more time or not
parallel process: reaction time is independent of set size, used when there is a pop-out stimulus, a feature search
serial process: with increased set size, higher the reaction time, used in conjuction search, where you have to use feature integration
negative = target absent, positive = target present
it will take longer if the target is absent no matter what because you have to check every single stimulus to make sure — exhaustive search
Target absent slope is higher than target present slope since you have to look through every elementt– 2 to 1 ratio
if the target is present you only look at half of the stimuli!
Look at Review for Diagram.
What is Feature Integration Theory, and how did Treisman’s data provide support for it?
Idea that visual objects get dissected in terms of features (ex. Colors, orientation, etc.) before they get perceived as objects
dissection does not require attention, comes for free – feature maps are free
We start putting feature maps together in order to filter and focus, ex. We need color on top of shape to identify green square
when participants had to put multiple feature maps together to find the target (conjuction search), they took longer (larger reaction time)
Faster reaction time when they only needed to look at one feature (feature search)
Treisman assumed that search was exhaustive and self-terminating. Define these terms.
self-terminating search: once the target is found, you end the search
exhaustive search: each element will be checked until you are absolutely sure the target is not there
Townsend argued that positive slopes of reaction time versus set size do not necessarily implicate serial search. Explain his ideas about limited and unlimited capacity parallel search.
limited capacity parallel search: each element is getting less attention, dividing our finite resources, everything is slowing down – so positive slope that depicts more elements, makes you slower, therefore reaction times are longer. Therefore, you could be in parallel-search mode, but your attention is just divided, so you end up getting less information per second from each stimulus
unlimited capacity parallel search: feature search is unaffected by the set size, pop-out stimulus
Townsend thought that multiple target search might better discriminate serial from parallel processing. Why might reaction times be faster when there are lots of targets than when there is just one? How would this happen only if search is parallel?
as information is coming into the visual system about the environment, the more similar stimuli you perceive, you become more certain the target is out there
the more targets you get, the earlier you can stop the trial — early returns can outweigh the thinning of attention through limited capacity parallel search
only would work with parallel search because you need to see all the stimuli at once to note the similarity in order to keep the reaction time shorter — if you had to do this serially, it would take as long as it does to find one target
In reality, people do not search every display exhaustively. How do foraging strategies influence target finding in visual search experiments where targets are relatively scarce?
it is not rational for animals to search a place for food exhaustively
animals carry a limited amount of energy, so they innately move on if there is a low probablity of food
need to relocate to a place where the likelihood of food is higher
Levy flight: we look around for awhile then and move on if you are unsuccessful, this animal may miss food but is rational
Explain the difference between explicit and implicit methodologies.
Implicit test: a person’s behavior tells you their state of mind, the participant is unaware of the purpose of data collection and therefore unaffected by demand characteristics, learn about structure of mind through data
Explicit test: the participant tells you their state of mind, the participant knows exactly how you want them to behave/what you are testing, meaning this test is affected by demand characteristics
What are demand characteristics, and how do Kosslyn’s results from the mental scanning task reflect them?
demand characteristics: participants form an interpretation of the experiment's purpose and subconsciously change their behavior to fit that interpretation, participants behave in a way that they think is going to please the experimenter
Kosslyn did not give the participants any indication of how long the mental scanning was expected to take — no right or wrong answer
the participants wanted to respond “correctly” for him so they all ended up “mentally scanning” for around 1.5 seconds — accidentally measured humans’ inner sense of time
Describe Shepard’s mental rotation task, and diagram the results. What does this tell us about the imagination?
implicit experiment on imaginative rotation
The participant has to decide if the blocks are the same, just oriented different ways
Larger the angular deviation, longer it takes you to tell if the blocks are the same are not
Inference that we do things at constant velocity – if we have to rotate to larger angle, it will take longer
There is no teleportation in imaginative rotation — it’s euclidean
Why does Shepard’s study provide better insight into the imagination than Kosslyn’s? Explain in the context of explicit vs. implicit methodologies.
Shepard did not tell his participants that we was measuring their memory reaction times, just gave them the objective task, so the data was unaffected by “demand characteristics” — implicit
Kosslyn tod them he was measuring memory and timing them, so they all tried to act in a way that was “correct” — explicit
In the method where the final orientation is given in the Shepard letter experiment, knowing the final orientation but not knowing the letter identity prevented people from being able to get started on mental rotation. Why? What do people need to be able to mentally rotate even if they do not have a specific form in their imagination?
Mental rotation needs a reference → If you don’t know the letter’s identity or orientation, you have nothing to rotate — cannot operate in the abstract
Without a clear shape, the brain can’t start rotation because it doesn’t know what it’s working with.
but if all the letters face right, or all the letters face left, they can create a frame and speed reaction time without a letter
The study with four dots on the first frame and the arrow on the next frame also involved mental scanning. Again, using the implicit versus explicit distinction, explain why this is a better scanning experiment.
The study with the four dots was an implicit memory test — is the arrow pointing at the dot?
You can learn the 4 dots at a glance better than a map
Participants use their memory without being told to do so
Linear data – more dots, larger reaction time
How did Gilden and Blake determine that the visual imagination uses visual areas of the brain?
Gilden’s experiment: Tested if retinal movement adaptation affects imagined motion.
Findings:
Motion surge always happens in the opposite direction of the retinal adaptation.
Retinal adaptation affects imagination, but only for stationary objects.
This proves that visual imagination uses the same brain areas as actual vision.
