Language & Decision Making J. Lauwereyns, Ph.D. Professor Faculty of Arts and Science Graduate School of Systems Life Sciences Kyushu University jan@sls.kyushu-u.ac.jp
Language: Unique to humans?
Evolution and Physiology of Language Human language is different because it is more productive can produce new signals to represent new ideas Chimpanzees can learn to communicate using sign language or symbols, but different from human language symbols used to request but rarely to describe seldom recombine in new combinations say more than they understand, the opposite of children
Language as a Special Module Humans have evolved with something that enables them to learn language easily Chomsky and Pinker: a language acquisition device children learn language with ease, including children of deaf parents deaf children learn sign or invent one of their own not likely a separate module since most language areas used for other functions, e.g., memory, music perception intelligence may be by-product of language
Broca vs Wernicke
Broca’s Aphasia Also called non-fluent aphasia severe deficits in language production caused by damage to Broca’s area, and other cortical and subcortical structures difficulty pronouncing, gesturing and writing as well as understanding complex speech uses and understands nouns and verbs more easily than closed-class words, e.g., prepositions, pronouns ignores grammar and relies on inferences but, can usually recognize when something is wrong with sentence even if they cannot correct it
Wernicke’s Aphasia Also called fluent aphasia caused by damage to left temporal cortex seriously impaired language comprehension difficulty finding the right word and trouble recalling names of objects grammatical but often nonsensical speech perhaps because can’t “find” words due to rapid speech but, can pronounce clearly, fluently and rapidly
Wernicke: Comprehension, Meaning Broca: Production, Syntax
What about language on the left?
What about language on the left? Lateralization of Brain Function Two hemispheres are not mirror images of each other left hemisphere controls right side of body right controls left side taste and smell input to same side Lateralization is the specialization of labor between the two hemispheres left hemisphere specialized for language right specialized for complex visual-spatial tasks and synthetic processing
Handedness and Language Dominance Right handedness a heritage 10% of people are left-handed or ambidextrous 90% of prehistoric drawings show tools in right hand most chimps and other primates are right handed Left handers have equal as well as left or right hemisphere dominance for speech if right is dominant, left hemisphere contributes more to spatial perception Corpus Callosum is thicker for greater communication
Not quite as famous as Sir Edmund Hillary, but…
Where does Corballis get his idea? Corticol control of manual movements Primates acquiring sign language The mirror system in monkeys Left hemisphere for speech and hands Deaf use sign languages with full syntax Nonverbal gestures during speech FOXP2 gene mutated about 200,000 years ago
FOXp2
Where does Corballis get his idea? Corticol control of manual movements Primates acquiring sign language The mirror system in monkeys Left hemisphere for speech and hands Deaf use sign languages with full syntax Nonverbal gestures during speech FOXP2 gene mutated about 200,000 years ago
The mirror system Ventral premotor area – monkey homologue of Area 44 in frontal cortex, that is, Broca’s Area Studied by Rizzolatti and co.
The mirror system Neurons in ventral premotor area …activated both when the subject performs an action and when the subject observes someone else perform the same action Abstract action representation This system likely plays a role both in recognising and planning actions (“thinking about actions”)
Importance of the mirror system? Understanding action? Origins of language? Empathy? Morality? (some other day…)
On reasoning and decision making
On reasoning and decision making More complex with language Consider context Imagine different scenarios…
Most basic structure for decision making… Response Stimulus Stimulus – Response Matrix
Signal detection theory
Bias
Consider different decision contexts…
Consider different decision contexts…
Consider different decision contexts…
Bias
Sensitivity
Sensitivity
Ways to improve sensitivity…
Ways to improve sensitivity…
Ways to improve sensitivity…
How does it really work?
General increase
General increase: Prospective, additive Bias in anticipatory activity Linearly enhances sensory activity Response = Input + Reward Bias Prefrontal cortex, basal ganglia Superior colliculus
Improved discrimination
Improved discrimination: Synergistic, multiplicative Sensory properties Non-linearly enhanced by reward Response = Input * Reward Gain Prefrontal cortex, parietal cortex Superior colliculus
Dopamine
Dopamine
Dopamine Excitation Synergistic, multiplicative Disinhibition Sensitivity Prospective, additive Bias
How do we process conflicts? Paradox Immediate reward versus Delayed gratification
The classic: Stroop James Ridley Stroop, inventive priest Present participants with a word printed in a certain colour GREEN Name the colour Interference from irrelevant word RT: Incompatible > Neutral > Compatible Evidence of conflict
fMRI study:McDonald et al Using a “cued Stroop” task Trial begins with “word” : read the word “colour”: name the colour Task instruction changes trial by trial Separate effects Instruction-related activity Response-related activity
Response- related activity RED GREEN related activity Instruction- RED Congruent stimulus Incongruent stimulus COLOUR NAMING RED GREEN related activity Instruction- “red” “red” RED GREEN WORD READING “red” “green”
Interpretation In DLPFC: Stronger activity in “colour” trials than in “word” trials Effects of task instruction, but not congruency Especially before target onset (during preparation) In ACC: Stronger activity in “incongruent” trials as compared to “congruent” trials Effects of congruency, but not task instruction Especially after target onset, or even after response
Conclusions Dorsolateral prefrontal cortex Seems important for representing the task instruction Ordering what to do Anterior cingulate cortex Seems involved in situations of conflict Performance monitoring Evaluating what you do