Introduction to Cognitive Science

• A few more things on perception
• Attention
– Description of Attention
• What is attention?
• What are some features of attention?
– Models of Attention
• How does attention work?
• What is the underlying mechanism?
– Larger theory of attention
• What is attention for?
• How does attention fit into the overall ‘cognitive architecture?)

• Many people believe vision (or any other form of perception) to be a purely “bottomup” process: starting with the raw sensory input, we recognize edges, bars, blobs, and other basic optical features. These features can then be combined (e.g. via the recognition-through-component approach) to recognize complex objects.

• I can look at the same image, and consciously choose to pick up on certain features as opposed to others.
– E.g. doing a jig-saw puzzle, I can see the red pieces
(and not notice the green pieces)
• Neisser’s experiment of 2 overlaid baseball games
• Selection problem: how do I (my visual system) select what features to pick up on?
– Pure data-driven models of perception cannot explain this.

• Another argument against pure bottom-up processing is that it seems inefficient and a ‘waste’ of resources.
– E.g. I don’t need to completely parse every few milliseconds everything I see:
• “Hmm. I’m in a classroom now.”
• (20 msec later) “Hmm. I’m in a classroom now.”
• What makes more sense is to combine raw incoming data with already processed information.
– In fact, this would probably make perception less error-prone.

• In fact, what makes much more sense is that higher-level processes actively drive perception to a considerable extent, in that it ‘asks’ the visual system to look for certain things in the environment that the higher-level processes need.
– Indeed, a lot of neurological pathways go ‘against’ the visual processing flow from raw data to …?
• Such need-only based, purposeful, perception is something we can call ‘active’ perception: Much different from the kind of ‘passive’ perception idea one gets from a purely bottom-up model.

Active Perception implies Selective Perception!

• Neurological evidence suggests that I use same resources for direct perception as well as mental imagery (seeing something ‘in my mind’s eye’)
• Still, I know the difference between a direct perception and an imagined one.
• Again, a top-down process would easily explain this; a bottom-up process has a much harder time with this.

• Could our experience of the world be something that incorporates predictions of what will happen in the future?
– Could be used to make up for lag between sensory input and processed perception
– It’s a construction and guess anyway …
– And we can always modify based on actual input

• Attention is selective: I can’t attend to everything that’s going on around me
• Attention is divisible: I can pay attention to multiple things (multi-task)
• Attention can shift voluntary: I can consciously switch attention from one thing to another
• Attention can shift involuntarily: Sometimes my attention is drawn to something, whether I want to or not

• Suppose you are at a Cocktail Party, with many conversations taking place around you.
– Selective Attention: you can’t attend to all conversations at once
– Divisible Attention: you can converse while getting a drink at the same time
– Voluntary Attention Shift: you can consciously shift your attention from one conversation to another
– Involuntary Attention Shift: you suddenly hear your name being spoken by some people across the room

• Filter theories of attention try to explain why attention is selective
• Attention is directly linked to perception
• Many models of perception see perception as some kind of process from raw data to interpreted information.
– E.g. vision: raw retinal image -> edges/blobs -> shapes -> objects
• Filter theories of attention postulate that there are certain ‘filters’ along this informational pathway that only makes certain information pass, but not other.
• Where along the pathway are these filters?

• Some people proposed that there are filters fairly early on in the pathway
– Evidence: Dichotic Listening Task
• Set Up: Subjects had headphones with different input on each ear. Subjects had to pay attention to one ear’s input
• Result: Subjects could tell that something was being said in other ear (as opposed to, say, music being played), and also whether the speaker was male or female. But they could not tell whether it was English or Russian, or nonsense (e.g. reversed) speech
• Interpretation: Basic physical features (speech vs music, pitch) were processed, but not much more. Hence, a filter fairly early on.
• Application: Cocktail party: Based on low-level features such as the direction of where the sounds are coming from, or the pitch of the words spoken, you can filter out everything except the one conversation you’re paying attention to.

• Objection:
– Certain discriminations presumably only happen fairly late in the pathway.
• Your name being spoken at a cocktail party.
– Recognizing your name requires much more advanced auditory processing, i.e. this information must be getting beyond an early filter.
• Neisser’s overlapping baseball games
• So, other models were proposed:
– Late Filters
– Multiple Filters
– Movable Filters
– Leaky Filters
– Etc.
• Much research done, but no clear picture has emerged

• Try a different tack: focus on the divisibility aspect of attention
• Attention is seen as a resource (a kind of mental
‘energy’ or ‘capacity’) that is in limited supply.
• Hence, while you can divide (distribute) your attention over several things, you can’t pay attention to everything

• Experiment: Subjects wore headphones, had to pay attention to story told in one ear. But subjects also had to pay attention to:
– Condition A: Words spoken in other ear
– Condition B: Words presented on screen
– Condition C: Pictures presented on screen
• Result: Performance was worst for condition A, best for Condition C. B was in between.
• Interpretation: There was more ‘task interference’ in condition A, presumably because this involves some of the same neural resources.

• Filter views have more of a ‘bottom-up’ feel:
– the filters let certain information through or not, and they decide what you (involuntarily) become aware of
• Resource models have more of a ‘topdown’ view on attention:
– you can (voluntarily) decide what to pay attention to; whereas

• Let’s look at attention from yet another perspective, and ask the following question: Even though attention is divisible to some extent, why is attention in most cases focused on one thing?
• Why, indeed, is there something like attention at all?!
• Especially in the light of our brain being able to do powerful parallel processing without any problem, this seems like a interesting question.

• One possible answer is that if we were to attend to several things, our body may have to react in incompatible ways
– e.g. one cognitive activity will want to make our body do one thing, and another something different. In short, we’re physically being pulled in two different ways … which we can’t physically accomplish.
– So, even though from a neurological, computational, or purely psychological point of view it should be perfectly possible for attention to be much more divisible than it is, the physical consequences it has for our body make it so that we have to focus on just one thing.

• The view of situated cognition gives additional support for this idea.
• If some cognitive task requires physical interaction with our environment, then we are clearly limited by having only one set of hands, one set of eyes, etc.
• And even if this is internalized (e.g. internal dialogue or mental imagery), we’re still using the resources that were geared for one voice, one set of hands, eyes, etc.

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• So, maybe the fact that we have one mind (or at least have a sense of having only one mind) is a natural result of having one body.
• In other words, having one mind may be an illusion forced upon us by having one body.
• Indeed, sometimes the illusion can’t be held up, and some people seem to have multiple minds:
– (from clinical/abnormal psychology) multiple personality disorder
– (from neuroscience) the two hemispheres of the brain doing quite different things

• So how divided is attention really?
• Certainly when high-order cognitive processes are involved, it is next to impossible to divide attention:
– can someone really do a calculus problem while having an intense debate with someone about some complex issue?
• And is the ‘younger generation’ really better at multi-tasking?
– Can multi-tasking be learned or trained?

• Researchers from the University at
Stanford found that selfdescribed ‘heavy media multitaskers’ were not any better at multi-tasking than selfdescribed ‘light’ or
‘non’ multi-taskers!
– “Cognitive control in media multitaskers”, Ophir et al.
Proceedings National Academy of Sciences, 2009
• This seems to go against the view that multi-tasking can be learned.
• But what would explain this?

• Here’s a possibility: maybe much of what we call multi-tasking is really inter-tasking: the interweaving of several tasks
– not unlike the way a modern computer simulates parallel processing by quickly going back and forth between different processes.
• However, such interweaving requires high amounts of logistics, organization, and … focus!
– So, maybe heavy multi-taskers are really people with less focus … and thus more easily distracted