bcs 111 quiz 2

Lateralization

The tendency of certain brain functions to be dominant in one hemisphere

contralateral processing

visual processing: what our left eye sees, what our right brain processes

sensorimotor processing: what our left hand feels, what our right brain processes

In split-brain research, what anatomical structure is surgically cut to separate the brain's hemispheres?

The connection between the left and right hemispheres (corpus callosum).

second step of split-brain research

Ask patient to touch or see an object with either left hand/eye or right hand/eye 

third step for split brain research

see if patient can recognize and name the object

What was a surprising finding regarding the daily behavior of patients after split-brain surgery?

There was no obvious negative effect on their daily behavior.

Stimulus presented to left visual field or touch with left hand (can recognize stimulus?)

yes

Stimulus presented to left visual field or touch with left hand (can name stimulus?)

no - info can't be sent to left hemisphere (language region)

Stimulus presented to right visual field or touch with right hand (can recognize stimulus?)

ye

Stimulus presented to right visual field or touch with right hand (can name stimulus?

yes - info processes on the same side of language regions (left hemisphere)

Evolution of the brain

Brain larger (also frontal lobe), jaw and teeth smaller (allows us to produce wider variety of speech sounds)

In non-human primates, what is the presumed original function of the brain region analogous to Broca's area?

action planning and execution 

Original function of Broca's area (how has it evolved over time?)

Fossil records = show size of brain (Broca's cap) - show at the time humans developed some sort of advanced/language function

What evolved function is associated with Broca's area in humans, related to patterns?

Sequential pattern recognition, processing, and learning.

What type of evidence from fossil records suggests the evolution of Broca's area?

The size of the brain, specifically the 'Broca's cap'

In Reber's (1967) artificial grammar learning experiment, which group showed significantly higher accuracy when writing out sequences?

The group that learned the grammatical sequences.

Artificial grammar learning (AGL) - Reber et al

• test whether people can unconsciously pick up patterns/sequences;
  

• two sets of sequences: grammatical and random;
  

• one group learned grammatical, one learned random (does not follow diagram);
  

• wrote out sequences after learning each one;

Petersson et al.

grammar similar to Reber;
letter strings;
training phase: exposure to many grammatical sequences multiple times, after each sequence-type out right away, 5 days of training;
testing phase: sequence classification task

Petersson et al. (RESULTS)

ungrammatical sequences took more effort to process than grammatical counterparts --> larger activation of Broca's area when seeing ungrammatical sentence

role of perception in cognition

receive input --> perception --> recognize?
yes --> match to data base --> recognition
no --> external resources --recognition --> database

What if someone cannot perceive/sense anything? 

no recognition, can’t be stored in database

In the 'What' stream of perception, what is the term for the real object in the world?

distal stimulus

In the 'What' stream of perception, the _____ stimulus is processed through the visual cortex.

proximal stimulus

In the 'What' stream of perception, what is the term for the object as interpreted by the temporal cortex?

the percept

Recognizing an object by its commonly accepted name requires both a pre-stored memory trace and what other process?

recognition (memory recall)

Gestalt principles

• ways for the brain to infer missing parts of a picture when a picture is incomplete;
  

• holistic processing;
  

• proximity; similarity; continuation; closure; common fate

proximity (gestalt principle)

•  grouping by the distance between items 

Similarity (gestalt principle)

• grouping by the similarity between items 

Closure (gestalt principle)

• perceptually “fill in” the missing parts (lines or elements) 

when two lines intersect, we choose the simpler interpretation (each line continues after the intersection point) instead of two odd shapes

Common fate (gestalt principle)

items moving in the same direction are grouped together

Feature analysis 

• Use certain distinctive features to recognize an object or event 

• Feature analysis approach: single object

• Features instead of the whole unit used for recognition 

  • Decompose an object into geons (the building block of an object)

• Feature analysis approach: visual search task

• Search latency (the time needed to find the target) positively correlated with the similarity between the target and the distractors

  • Higher similarity among letters make it harder to detect the target → longer search time (slower) 

Categorical perception 

The phenomenon by which the categories possessed by an observer influence the observer’s perception

two neural pathways in perception

dorsal and ventral stream 

dorsal perception pathway

where pathway (going up)

ventral pathway perception 

the where pathway (going down)

Why study prototypes and exemplars in the very first place

• To help us understand 

  • How we recognize and categorize an object

  • The structure of our categories/concepts 

Prototype

•  match the input with a pre-stored “prototype” (representative of the category)

exemplar 

match the input with each stored input in memory 

Feature analysis

use certain distinctive feature of the input for recognition 

Evidence for prototype: Posner and Keele (1968)

• Training: present one distorted dot pattern at a time (each pattern is derived from one of the 4 original prototypes) (prototype is NOT shown to participants in this phase) 

  • Classification task

1. Seeing a distorted dot pattern (target stimulus) → 

2. Compare it to 4 options: each option is another distorted dot pattern derived from one of the 4 original prototypes → 

3. Judge if the target stimulus belongs to any of those 4 categories 

• Testing: three types of target stimuli: new distortions (not seen before), old distortions, original prototype (not seen before)

  • Classification task: same as in training 

Key points for Posner and Keele’s study 

• The same task in both training and testing

• Feedback given during training 

• NO feedback during testing

• Prototype formed during training 

• Significant implications of this study 

  • Formation (or reconstruction) of a prototype by seeing/hearing many variants (distorted dot patterns, faces, or words) 

  • Normalization across variants to reconstruct the prototype 

Exemplar matching 

• A large number of stored exemplars (eg, all kinds of frogs) 

• Ex. speaker’s unique pronunciation of the same word: each word produced by each speaker still has the same meaning 

Forming a prototype by generalizing across exemplars

• Ex. the same /p/ spoken by 100 people 

Issues with the exemplar model

• Memory capacity: store a large amount of exemplars?

• Novel objects: What if the new stimulus was never encountered before?

• Determination of recognition threshold: every detail of the object, or just the common features in the category? 

What does ABX task tell us about prototypes and exemplars?

• Comparison between exemplars within the category is not always easy

  • It is possible to detect the subtle differences within the category!

• Comparison between exemplars near the category boundary also not so easy 

• Comparison between prototypes should be a lot easier 

• Bottom-up processing

• (when signal quality is good eg a clear picture)

  • Prototype 

  • Exemplar

  • Feature analysis 

• the analysis of the smaller features to build up to a complete perception;
  prototype, exemplar, feature analysis;
  used when signal quality is good (ex: clear picture)

top down processing

use prior familiarity about the input

• Expectations

• Context effect 

  • Word superiority effect 

• Ex. word superiority effect in letter recognition task: faster letter identification when presented in a real world (contextual effect)

esp when signal is degraded

`Selective attention 

• Focus on a very limited events/objects/tasks

• For efficient processing 

Filter theory

irrelevant info filtered out through 'bottleneck' (ex: driving and don't notice Joan store)

• Limited capacity to process information 

How do we test selective attention? Dichotic listening task

• Participants repeat what they heard (from either ear) - shadowing

• Most people can repeat the attended message from one ear with very few errors

• If the unattended message sounds weird (eg backward speech) some people can notice the difference 

Evidence against the filter theory of attention: cocktail party effect.

can hear a fire alarm in a loud party while talking to friends, can still notice it

• Cocktail party effect

play subjects name to the unattended ear and see if participant notices;

• only 33% heard their name if not informed about possibility of hearing their name before the experiment

evidence against filter theory  Switch ears (Treisman)

Switch ears (Treisman)

people repeated a few words from the unattended ear right after switching ears;
people unaware of switching and their own repetition of the words from unattended ear;
evidence against filter theory

Attenuation

• Irrelevant info is tuned down 

attenuation: Treisman (1960)

• unattended message not completely blocked or filtered out;

• 
  

• the "volume" is turned down on unattended ear;
  

• depending on the message, some info might still be processed;
  

• top down influence on attention

DLT task (filter theory)

only hear message in attended ear;
not a valid account given the findings from DLT task

DLT task (attenuation theory)

• Higher attention level for familiar/important content 

Spotlight approach

we perceive everything but actively cast a "spotlight" on the target - things on the edge of the spotlight can still get processed;

• size of spotlight varies with size of object;

• control where to direct our attention

Schema

Only take what you need; everything else untouched (not even entering the processing pipelines)

• only relevant information enters the processing route

Divided attention 

• How many tasks we can perform at the same time

• It’s tested using dual-task experiments (like Allport et al., 1972)

•  where participants are asked to do two things at once (for example, a shadowing task—repeating words they hear—while also doing a memory task). 

• These experiments show that performance usually suffers when trying to split attention, because attentional resources are limited.

Automatic Processing 

• Posner and synder (1975)

  • Three criteria 

1. Processing occurs without intention 

2. Unaware of the process of noticing the target

3. Not interfering with other mental activity 

• Requires very little mental effort to process 

Controlled Processing 

• When you have to actively direct your attention and it requires a lot of mental effort 

• Ex. finding a person with very specific feature in a crowd is controlled processing, because you can’t just spot them instantly — you have to carefully search 

Actively shift your attention from one thing to another → requiring a lot more mental efforts than automatic

• Schneider and Shiffrin (1977) → tests for automatic processing 

• Consistent mapping condition:

  • Target and distractors are different types of stimuli 

  • Target in the current display won’t appear anywhere in the next display 

• Automatic processing (finding the one that stands out) 

• Varied mapping condition

  • Target and distractors are the same type of items (ie letters)

  • Target in the current display CAN still appear as a distractor in the next display 

  • Controlled processing 

• In the consistent mapping condition, the targets and distractors were different types of stimuli (for example, numbers as targets and letters as distractors).
  
  

• Importantly, a target from one trial would never appear as a distractor in the next trial.
  
  

• Because of this setup, participants could detect the target almost automatically — it “popped out” without needing much effort or attention.

how did this study show automatic processing? Schneider and Shiffrin (1977) → tests for automatic processing 

1. It happened without intention.
   
   

2. Participants weren’t always aware of how they spotted the target.
   
   

3. It didn’t interfere much with other mental activities.

Controlled Processing: Attention shift task

• Switch between two features of a stimulus 

  • Control what you need to attend to at the last moment 

• Measure cost of switch/shift 

• The attention shift task measures how flexible our attention is and how much effort it costs to switch between different aspects of a stimulus.

Controlled processing

• requires careful control of your selective attention, requires a lot more mental effort

• The role of primary somatosensory cortex in attentional control: evidence from fMRI

  • Zimmermann et al (2012)

• Finger sequences

• Training: either think about the action of moving your fingers (internal focus “IN”) OR focus on the physical button presses (external focus “EX”) 

• Takeaway: This study shows that different brain regions help control attention depending on whether you’re focusing on internal body actions or external physical cues. Switching attention between these modes requires more effort and recruits extra brain areas.

consistent mapping 

automatic procesing 

varied mapping

controlled process

controlled process

Shifting attention from the external stimuli to internal state

What happens if there’s damage to the right parietal lobe?

Hemineglect

Hemineglect

• unaware of the objects in the visual field contralateral to the lesion site;
  

• reduced awareness of stimuli on one side of space, even through there may be no sensory loss

Three major memory processes

encoding, storage, retrieval 

Encoding

• the process that converts input into a memory trace

storage

the retention of encoded information over time

Sensory memory

the immediate, very brief recording of sensory information in the memory system;

Retrieval

the process of getting information out of memory storage

Types of sensory input

visual (iconic); auditory (echoic); gustatory (taste); tactile (touch); olfactory (smell)

How do we test iconic memory?

recall task; partial report technique

recall. task

recall the letters shows on screen; then see a dark screen and recall the letters you can remember

Partial report technique

report only a portion of the stimuli according to the given cue (recall task: only recall one row of letters when you hear a beep);
allows for more efficient processing

Whole report (recall task) vs partial

whole: no cue --> 35-45% reported --> higher cognitive demand;
partial: recall better when cued; timing of cue matters; delayed cue (about 1 sec) not helpful); retention < 1s

when does iconic memory not work

• If the letters are grouped by categories (like vowels vs. consonants) and you’re cued to recall only vowels, performance doesn’t improve. That’s because iconic memory is formed before the brain has time to categorize letters at that level.

what is iconic memory specific to

visual processing

• Similarly, if the cue is based on phonological information (like “recall the letters that rhyme with P”), it also doesn’t help. This is because iconic memory is specific to the visual modality—it’s about raw visual features, not sounds.

Testing ecohoic memory 

hear letters from 4 channels at the same time then recall all letters (whole report vs partial report)

Partial report

• helps the same way as in iconic memory;
  

• cued by sound category IS helpful in echoic memory (contrary to iconic and slightly larger capacity than iconic);
  

• Auditory mask (a suffix) presented right after the list hinders recall of auditory stimuli

Sensory memory summary

• Modality specific: each sense has its own corresponding sensory memory 

• Very brief (~1 sec) (echo lasts a bit longer) 

• Brief storage of under-processed information 

modality specific

• each sense has its own corresponding sensory memory