bcs 111 quiz 2

Lateralization of functions

Certain functions are lateralized (dominant in one hemisphere)

split brain research

Split brain research

1. cut the connection between left and right

2. ask patient to touch or see an object with either

3. see if patient can recognize AND name the object

stimulus location: left visual field/left hand touch

can recognize but not name since info can’t be sent to left hemisphere (language region)

stimulus location: right visual field/right hand touch

can recognize and name since info is processed on the same side of language regions (left hemisphere)

Brain evolution: an example from the function of Broca’s area

• get information from archaeological records

• compare the brain size to see how much has changed over time and also the shape of our skull

• most obvious change you can see is that the brain gets larger and teeth/jaw gets smaller

Implicit Learning of Sequences

Occurs anytime in our daily life

• Learning new phrases or sentences/ new sound sequences → Linguistic 

• Actions/Sports → non-linguistic

What do we know about the original function of Broca’s area?

• How has its function evolved over time?

• Fossil records

  • Size of brain, especially the “Broca’s cap”

Broca’s Area activation in finger-tapping task

pars opercularis

Broca’s Area activation in articulation

pars triangularis

Grammaticality of linguistic sequences

Sentence level

Phrasal level

Phonological level

Sentence Level (grammaticality of linguistic sequence)

“I love cognitive science.”

• “I coffee some want.”

Phrasal Level (grammaticality of linguistic sequence)

“within a month”

• “within month a”P

Phonological Level (grammaticality of linguistic sequence)

[sprin] ‘spring’

• [psrin]

How can “non-linguistic” sequences be “grammatical” or “ungrammatical”??

a simple analysis of action sequence

Experiment of sequence learning: Artificial grammar learning (AGL)

Reber (1967)

• 2 sets of sequences: grammatical and random

• 1 group learned grammatical, another learned random

• wrote out the sequences after learning each one

• accuracy significantly higher in grammatical than random seq 

fMRI study of artificial grammar learning

Petersson et al. (2022)

• grammar similar to Reber (1967)

• Letter strings

• Training phase:

  • Exposure to many grammatical sequences multiple times

  • After each sequence, typing it out right away

  • 5 days of training

• Testing phase: sequence classification task

Ungrammatical sequences took more efforts to process than the grammatical counterparts —> larger activation in Broca’s area while seeing ungrammatical sequence

Implications of Petersson et al’s (2012) fMRI study

• processing of artificial grammar similar to that of real linguistic sequences

• implicit learning of sequences without prior knowledge

What was the original function of Broca’s area?

• Presumably closer to how it works in non-human primates (action planning and execution, etc) than how it works in humans

• sequential pattern recognition/processing/learning

Perception vs Recognition

Typical perception route:

• distal stimuli (real object in world)

• proximal stimuli (object processed through visual cortex)

• percept (object interpreted through temporal cortex)

Recognition of features or patterns in a novel object (e.g. shapes, colors, size, etc.) isn’t too difficult

Recognition by its real label is not always easy — it requires both a prestored memory trace and memory recall

• when novel object name is unknown, can still label/describe in our own way

• when encountering novel object again, may be able to recognize either by its real label or by own label/description

Gestalt Principles

Proximity, Similarity, Continuation, Closure, Common fate

gestalt principle: proximity

grouping by distance betweenges items

gestalt principles: similarity

grouping by similarity between items

gestalt principles: continuation

when 2 lines intersect, we choose the “simpler” interpretation (each line continues after the intersection point) instead of 2 odd shapesge

gestalt principles: closure

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

gestalt principles: common fate

items moving in 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 any object)

feature analysis approach: visual search task

search latency (time needed to find target)

search latency positively correlated with the similarity between the target and the distractors

higher similarity among letters makes it harder to detect the target —> longer search time (slower)

Categorical perception

phenomenon by which the categories possessed by an observer influences the observers’ perception

why do we study prototype and exemplars

to help us understand:

1. how we recognize and categorize an object

2. the structure of our categories/concepts

perception/recognition of unfamiliar objects

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

• exemplar: match the input with each stored instance in memory

• feature analysis: use certain distinctive feature of the input for recognition

Evidence for prototype

Posn