1/123
this set has flashcards for the second half of the sem
Name | Mastery | Learn | Test | Matching | Spaced |
---|
No study sessions yet.
#7 Attentional Blink: RSVP task procedure + conclusion
A stream of images one after another rapidly to test how participants deal with info under pressure. When Ps had to respond to multiple targets, they missed the 2nd target when it rapidly followed the 1st one. It demonstrated the effect of attentional blink: With the presence of distractors, people respond more slowly.
#7 Attentional Blink: RSVP task, why do we miss the second target?
There are two tasks: pick up target & suppress distractors; hence need to rapidly switch tasks. Hence, the (1) task switching paradigm; time pressure & multi-task pressure.
#7.1 Study A Jersild (1927) task-switching experiment [AABB]
Results demonstrated a general slowing reaction time. Time cost was bigger when you have to perform different tasks with the same stimulus, compared to different stimuli.
Explanation: Is that because people simply forget which task to do? No, because generally, the trials involved switching took more time to complete task > repetition (Fagot 1994)
#7.1 Study B Rogers & Monsell (1995) AABB paradigm
Frequently used in other research as well. The stimulus (Letter+Number) was presented in one of the four grids. When it appeared at the top, you have to differentiate whether it is a vowel or constant; odd or even when bottom. There were trials involved switching of tasks and trial that didn't.
Conclusion:
#1 Much slower when have to switch due to task switching cost. Practice reduces the task-switching cost but still exist even after 10-hour practice session.
#2 Switching to the easier task incurs the greater cost. (e.g. from colour naming to word naming in Stroop test)
Explanation:
Demonstrated disengagement effect. The original hard task requires effort, concentration and investment of energy input. Disengaging from an easier task is easier.
#7.1 Theory A Rogers & Monsell (1995) Task-set Re-configuration (TSR)
All attention is specifically configured for a task for a situation. e.g. athlete ready to run devote all attention in the task to wait for the signal. (?)
#7.1 Study C Sudevan & Taylor (1987)
They signalled the task before each trial to allow preparation time beforehand. By providing additional time to configured the task-set, it was believed that the task-switching cost could be reduced.
Conclusion:
Increased interval between trials reduces switch cost; yet the cost was not fully eliminated. Endogenous control could not fully explain the task-switching cost.
#7.1 Study D Meiran (1996),
Based on Sudevan & Taylor's experiment; but they eliminated 3rd variable, which was the delay form 1st trial (might get rid of existing task set).
Conclusion:
Short cue to stimulus interval led to large switch cost even when the delay was long enough. Exogenous control (interference from other trials) might account for the residual cost, which cannot be fully eliminated.
(Theory B)
#7.1 Theory B Residual costs <=> exogenous effect
(Study D) Residual costs are exogenous effects, "stimulus-driven". Attention still captured by the previous task and hence our brain is still processing old information.
#7.1 Theory C Rogers & Monsell (1995) Task congruity - congruent cues
Our brain creates short-cut to decide (learning for responses for stimuli). If the task is conflicting with the existing short-cut, the decision is slowed.
#7.1 Conclusions: Three main theories about task-switching cost
#7.2 Theory A Kahneman's capacity theory
An over-learned tasks consumes fewer resources and improved performance.
(Substantial practice: +performance, -effort, +re-structuring and co-ordination)
#7.2 Study A Shiffrin & Schneider (1977)
Asked Ps to search for target among a visual display and observe whether they can develop rule-based response to a series of targets, and to test the existence of short-cut (Task congruity). Procedure: Present a trial of display with the abs/present of target. Ps have to reply asap when they see the target, or tell that they see no target at the end of each trial. The trials differ in display frame (no. of target 2 or 4) and nature of distractors.
In Categorical group, there is a consistent mapping, i.e. target and distractors were drawn from two different sets. After practice, target starts to pop out. The difference between 2 targets and 4 targets gradually narrowed down because Ps start to rely on a short-cut. In mixed group, there is a varied mapping, i.e. target and distractors were drawn from the same larger sets. No possible short-cuts / simple response rule. Hence, difference between 2 and 4 targets remain exist.
#7.2 Automaticity / automatic process: Definition
1. Without awareness (can be done with mind-wandering)
2. Obligatory / deliberation conscious (Can't help to do it, e.g. reading)
3. Expenditure of resources
4. Fast
5. Rigid, habitual (e.g. S&S great difficulty when items in categorical group reversed; the routine was built for following)
#7.2 Automaticity / automatic process: Problem of definition
#7.2 Theory B Logan (1988)
Automatic processes are memory-based. They are record with memory traces and do not have to be built again. Information included the stimulus and how to respond, the two are pulled together. In other words, automaticity is memory retrieval of past solution. Without such memory or practice, thought and application of rules is required. A rigid habit is formed.
#7.3 Characteristics of woking memory
#1 Material needs to be refreshed, or else they will disappeared.
#2 There is a limited capacity of working memory, that is 4-9 items (7+/-2). Old info will be replaced by new info.
#3 WM=/=STM (neuropsychology)
#4 Continual interplay ./. WM and LTM (draw on vast storage of memory)
#7.3 Theory A Baddeley's Working Memory Model
There is a Central Executive that gives and receives output from a Phonological Loop, Visuo-Spatial Sketchpad, and Episodic Buffer.
#7.3 Definition of phonological loop
Sound-based working memory which maintains verbal and sequential (in order) information. It consists of "verbal store/inner ear" to generate sound in our mind AND "subvocal articulatory rehearsal process/inner voice". Information decays after 2 second unless it entered into the store through articulatory rehearsal.
#7.3 Evidence for phonological loop
Evidence A: Phonological similarity effect
Evidence B: Irrelevant / unattended speech effect.
Evidence C: Word length effect
Evidence D: Concurrent Articulation / Articulatory suppression
#7.3 Evidence for phonological loop: Phonological similarity effect
If the words sound the same, it is more difficult to remember them. Experiments demonstrated that it does not restricted to spelling or similar visual presentation. Ps translated word into sound. Hence, they represent info with sounds rather than picturing. If such effect is not observed, they replied on visual strategy instead. Usually not involved in LTM (relies on semantic).
#7.3 Evidence for phonological loop: Irrelevant / unattended speech effect.
If somebody talks to you, it interferes the serial verbal recall of visually presented material. No effect from white noise though. Only something that has pattern affect (nonwords, Arabic and backward speech).
#7.3 Evidence for phonological loop: Word length effect
(4-8 items limited)
Study B: Baddeley, Thompson & Buchanan (1975) longer list, harder to remember. less good memory. Same number of syllables but the words take different time to speak. Those don't have vocalization has the same effect too; but not for those who have brain damage in central programming of speech.
#7.3 Evidence for phonological loop: Concurrent Articulation / Articulatory suppression
Repeating syllables in their head affected serial recall. Ps filled up phonological loop by noises. Can be silent articulation / voiced. (Chewing gum no such effect; control). Phonological loop benefits vocabulary learning in children.
#7.3 Visuo-spatial sketchpad
An imagery based process of how you picture things around you. Involves visual imagery and spatial navigation. Corsi tapping task can be used to test: Ps had to remember the order of blocks that lighted to test their visual working memory capacity.
Concurrent speech did not interfere with V-S tasks. Not technically visual, blind people can navigate too. Impaired by different visual background
Application: sports, abacus
#8 Differentiate semantic and episodic memory
Both are declarative memory/explicit memory; as opposed to implicit memory (include procedural memory)
Semantic: a piece of knowledge about things
Episodic: episode that took place in that context
#8.1 Study A Murdock (1962)
Ps asked to remember 10-30 words, each presented 1s to 2s
Free recall test demonstrated [Serial position curve] primacy effect (transferred to LTM) and recency effect (still fresh in STM). If asked to count backwards, eliminated the recency effect but not the primacy effect.)
#8.1 Describe recency and primacy effects and the distinctions between short term and long term memory
Free recall test demonstrated Serial position curve. There was a primacy effect, memory more vivid at the beginning because it was transferred to LTM. Recency effect occurs because info still fresh in STM. If asked to count backwards, eliminated the recency effect but not the primacy effect, show that there is a distinction.
#8.1 Theory A Atkinson & Shiffrin (1968)
"Modal model" of memory stores
Information first comes to sensory memory. Attended information enters STM. Through rehearsal, information may enter LTM; LTM can be retrieved to STM. Without rehearsal and retrieval, the information is forgotten (This is an old model!)
#8.1 Problem of Theory A Atkinson & Shiffrin (1968)'s modal model
#1: Sensory considered as memory processes
#2: Rehearsal isn't what get material into LTM
#3 Interplay between LTM not a simple sequential transfer of information
#8.2 Two types of memory tasks (explicit)
Following Ebbinghaus tradition.
Explicit test, involves intentional retrieval
#1 First a study phase to study a word list. Can perform some tasks during study phase.
#2 Retention interval
#3 Recall test / recognition test.
Examples for recall tasks:
Free recall, serial recall and cued recall. Serial recall is difficult when it's artificial.
Examples for recognition tasks / discrimination task (episodic recognition; old vs new words)
Single item recognition (e.g. choice test), provide old + new items to test, record accuracy and maybe latency
+ve is can recall e.g. faces, but have multiple response bias (say 1 response most of the time, just by chance)
Hence, need to take into account False alarms. Subtract FA rate from hit rate.
#8.2 Implicit memory tasks
#1 Info not aware could leak into the mind and change the way we behave without being represented; hence semantic memory test
#2 Ps don't know there is a memory test
#3 May needs to go through a priming stage first
Lexical decision word: speeded word vs nonword decision for each letter string
Name a word, complete the stem "ki.."
Free association: Asked them what you think of when you see a word
#8.2 Korsakoff's syndrome; Schacter, Tulving & Wang (1981)
Cannot recall they saw the questions, but they answered the repeated, questions correctly. They do not have conscious assess to the information; yet their memory representation can be used in the test though.
#8.3 Study A Ebbinghaus' (1885) episodic memory tasks
Studied a series of nonsense syllables until he can recite the series perfectly twice. Recall of series was tested up to one year. Found a forgetting curve which was later replicated many times. Memory drops off over time in a systematic, non-linear fashion.
#8.3 Study B, C Jenkins & Dallenbach (1924), Baddeley & Hitch (1977)
Study B: Jenkins & Dallenbach (1924), separated by "sleeping". Learn information and have a memory test. Sleep group forgets less.
Problems: Dreaming might be interfering to and might actually consolidate memory. Alo, we can't test decay in months/years.
#2 Proactive interference (old blocks new) / Retroactive interference (new blocks old)
Study C: Baddeley & Hitch (1977) rugby players in the pub. Loss of detail correlated with time elapsed vs number of games? (new info) findings: interference>delay, retroactive interference
#8.3 Describe possible causes of forgetting and explain how experiments have shed light on forgetting, false memories and the possibility of memory inhibition.
Decay, proactive interference (old blocks new), retroactive interference (new blocks old)
False memory: misinformation, recovered memory
Inhibition: memories may be poorly retrieved because they are fragmented and difficult to interpret.
#8.4 Study A Elizabeth Loftus
Found misinformation effect (blue car turned right?) incorrect information given reduced accuracy.
#8.4 Study B Braun et al. (2002)
Found recovered memory. Rate adverts on characters on Disney Land (bugs bunny). They claimed they met Bugs Bunny in Disneyland (Warner Bros).
#8.4 Study C Deese, Roeidger & McDermott paradigm (DRM)
When shown bed dream wake..., Ps recall recognize sleep.
#8.4 Conclusion
#1 "Repressed" traumatic memories. Therapist could fabricate the memory by asking the questions (suggestions about repressed memories)
#2 Human difficulty with source memory/information. misattribute source to different places. there are techniques to create false memory. serious misleading questions
#3 Memory =/= real representation of what happened
#4 Memory retrieval is a re-constructive process. We are remembering the last time we remember it instead of the event itself.
#9.1 Theory A Level of Processing (Craik & Lockhart)
We can attend on different aspects in a word. e.g. orthography/phonology/meaning. A deeper level of analysis produces more long-lasting memory.
#9.1 Study A Craik & Lockhart (1972)
Cueing Ps by asking "how pleasant the word is", force them to think about the meaning vs questions about letter or rhyming. Semantic processing better than rehearsal to recall studied words. If you need to focus on the meaning, you need CONNECTIONS to other concepts. put together as a scaffolding to represent the meaning of a word.
#9.1 LOP and connections
LOP is about finding path / connections to organize thoughts/memory, easy to retrieve the stuff. Meaning of words connecting in a web in our mind. Mind built association that can be used later. Retrieval=run down the semantic network. Easier when there's a signpost.
#9.1 Study B Hyde & Jenkins (1973)
Semantic vs letter checking task; memory test vs no test instruction. Semantic>letter, intention doesn't matter. Best way to learn: try to find the connections. Not about intention to learn.
#9.1 Study C Jacoby, Craik, Begg (1979)
Evaluating size of differences, need to go through deep process to establish the smaller size differences. They have better memory for the word.
#9.1 Study D Craik & Tulving (1975)
Recall for words better for elaborate condition. deeper processing, existing knowledge interact.
#9.1 Problem of LOP
#9.2 Nature of flashbulb memory
#1 Unexpectedly vivid and detailed, contain a vast amount of information.
#2 Hugely consequential memory, emotional charged
#3 Change over time, according to current appraisal of the event
#4 Confidence of these memories is stronger
+ve memory never as important as the possibility of dying
#9.3 Study A Tulving (1967)
Multiple study and recall attempts with a list of 36 words. On each recall attempt, Ps remembered nearly 4 words that they had not recalled on the previous test. But they also forgot 3.9 words from the last test.
#9.3 Study B Stein (1978)
Semantic test (choose words from others) vs case task (how the word rocK looks); sentence study (does the word fit) vs letter-task (spot capital letter)
#9.3 Theory A Morris, Brandsford & Franks (1977)
Transfer appropriate processing (TAP)
Superiority of semantic study reflects that most memory tests are semantically based. Compared a standard recognition test with a phonological test requiring Ps to choose words that sounded like study words. Encoding: Does word fit in sentence (semantic) vs. Does word rhyme with .....? Semantic study better for recognition but not for phonological test. TAP: Transfer is best when test processes overlap with processing at study.
#9.3 Theory B State dependent learning
(Study C) Environment context provides cues for memory retrieval.
#9.3 Study C Baddeley & Godden
(Theory B) study word list dry vs wet, test dry vs wet.
Encoding & test same state, better (include emotion etc, environmental context)
#9.3 Study D Spitzer (1939)
Varied number & timing of tests, no feedback on test. Results showed that memory was more robust to recall later if tested earlier.
#9.3 Study E Roediger & Karpicke (2006)
Study-test alternation outperformed repeated study or repeated test.
#9.3 Disadvantages of MCQs & How to design MCQs?
MC gives people false memory, encoded the false options; also no memory retrieval effort need to be made. Need to be designed well. Make sure distractors are plausible.
#9.3 Erasing memories
Possible in rat? inject a drug to disrupt the reconsolidate/reconstructed process, delete fear memory on rat.
#10.1 Definition of representations
Representation = "aboutness", symbolic. Have a referent (what it refers too) and a sense of representation.
Analogue presentation=1:1 relat. e.g. photograph, analogue clock
Propositional=a set of rules to combine symbols, text, digital clock
#10.1 Definition of Imagery
The ability to operate the memory and revisit the situation.
#It allows us to imagine future situation and decide that to do right now.
#Imagine stuff that don't exist (entertainment)
#Practice without moving e.g. higher level sports, ask us to visualise them. get better by mentally rehearsal doing it.
#Build a mental map and orient ourselves.
Especially in hippocampus, consists of different kind of cells.
e.g. elephants, lab rats, london cab driver has larger hippocampus
#10.1 Theory A Paivio's Dual Coding Hypothesis
Pioneer in imagery research. Information is represented in both verbal and imaginal, visual code. Hence, it can be coded and stored into either or both system. Concrete words better remembered than abstract word because they can be stored in both, while abstract words only in verbal one.
#10.1 Three theories of imagery
(1) Paivio's dual coding hypothesis: concrete words
(2)Anderson & Bower, Conceptual-Propositional hypothesis: sentence
(3) Shepard & Koss, Functional Equivalence Hypothesis: mental rotation
#10.1 Theory B Anderson & Bower, Conceptual-Propositional hypothesis
We store things in propositional way. Predicate calculus representation of two things. Recognition task of sentences: the boy kissed the girl vs the girl was kissed by the boy. diff words same meaning. we store the meaning but not the analogue / the actual thing we exposed to.
#10.1 Evidence of propositional view
Theory B &
Participants are shown an image of two balls with a line in between that, there are two images that are exactly the same. One of them has the word barbells, and the other spectacles next to it. When asked to choose out of two images the group that had spectacles will choose the image with the smaller lines and vice versa.
#10.1 Evidence of analogue view
#1 Transformation: 4 and rotated D to a boat
#2 Size effect (Kosslyn): Elephant + frog vs frog + fly: easier to tell whether frog has a tail when with fly, because when it's with elephant, you have to zoom in
#3 Scanning: studied a map, imagine going from 1 location to another, pressed a button when arrive; react faster if the 2 locations are near
#10.1 Theory C Shepard & Koss, Functional Equivalence Hypothesis
Mental imagery is not simple analogue representation or abstract propositional. But relationship between objects in reality are functionally equivalent to and retained in our imagery. Share the same cog. mechanisms with perception, e.g. top-down vs bottom up.
#10.1 Evidence of functional equivalence hypothesis, Shepard and Metzler
Created different visual stimuli (3-D object vs its comparative stimulus) and Ps had to decide whether they are the same images. More it is rotated, longer time take to react. linear relationship between degree of rotation and reaction time. Supported that it is a mental rotation process with analogue effects and functional equivalence.
(Pylyshyn argued that it is affected by demand characteristics. but baboons show same rotation effect though they are faster than us. Males also faster.
*We do not have to form a rep and then rotate it)
#10.1 Cognitive resources of visual perception vs imagery
#1 Rotation aftereffects (Corballis & McClaren) If you look at clockwise image, when it stops, the aftereffect goes the other way. If mental rotation is of the same way, the task is speeded up; different way=longer time.
#2 Study B: Segal & Fuscella: Auditory detection task & visual detection task. Imagine a telephone ringing vs a visual scene. Differential interference effect. More errors when task & imagination congruent. Less when cross-modal. When we imagine something, it occupies the same mental resource with the same perception. Hence modality specific interference.
#10.1 Theory D Symons' Interference Hypothesis
We could afford visual hallucinations but not other, because we have to remain vigilance of the senses. Explains why these senses rare in dreams.
#10.1 Study C Bisiach & Luzzatti
Visual neglect syndrome with damage to right parietal lobe. Ps were asked two questions, looking at the dome, buildings near the plaza. Only told the left buildings. Asked them turn around; they told those in the other side. impairment goes beyond perception, but also imagery world
#10.2 Cognitive mechanisms shared by episodic memory and episodic foresight
#Similar brain structures involved. Hippocampus is both important in memory and foresight.
#More further away events become more abstract.
#Access to past & future events closely associated. e.g. Amensia, depression, schizophrenia, less vivid representation of episodic memory. Those who are able to tell what happened yesterday, more likely to tell what they're gonna do tomorrow.
#Capacity to mentally project ourselves to past & future events overlap.
#10.2 Functions of episodic foresight
#Extrapolation, past behaviour is the best predictor of future behaviour
#Reassemble basic element into novel scenarios and compare them
#The price to pay for the flexibility: retrieving memory = to reconstruct past events, easily manipulated memory. Constantly updating memory to justify current attitudes.
#10.2 Study A Clayton et al. (2003)
Scrub jays recover food caches according to what, where and when the food was stored. Worms vs nuts, time and location different. If come back 4 hrs later they look for the location of worms; if 120 hours they look for the nuts.
Problem: might only be associative learning/semantic memory
#10.2 Study B Redshaw & Suddendorf (2016)
A tube, drop something inside that you can catch in the bottom. Trials where Ps used 2 hands were recorded. 2.5 years old more tend to use both hands from 1st trial onwards. But the majority used 1 hand.
#10.2 Why is time travel uniquely human?
Associative learning? memory fades with passage of time. Double dissociation: factual knowledge about when and where, doesn't mean they can mentally time travel. Easier to explain that animals learn from associative learning.
#10.2 Evidence that imagery involves similar processes as perception
#1 Rotation aftereffects
#2 More errors when task & imagination congruent.
#3 Took away part of the lobe, mental image shrunk.
#4 There is greater activation in visual cortex when imaging than perceiving. top-down>bottom up.
#5 More vivid mental image, more response in occipital lobe.
#6 Recording of directional cells in motor cortex and the cellular directional vector rotation was equivalent to mental rotational data.
#11 Primates vs other mammals
Primates rely on vision more than smell, using their eyesight, lost their wet naked nose and don't have whiskers. The brain part for olfactory smaller. Colour vision. 3D vision, for you moving around the trees. Also have thumb, 5 separate digits and fingernails for gripping, relatively large brain to body size (encephalised)
#11 The principle of Parsimony, aka Lloyd Morgan's canon
End of 19th century, Lloyd Morgan recognised the problem of anecdotes and put forward the principle of Parsimony, aka Lloyd Morgan's canon. If you have multiple explanations for a thing, should make the least assumptions to explain the phenomenon. Go for the simplest one. Anecdotes: no best explanation, need systematic research.
#11 The Clever Hans phenomenon
Clever Hans is the horse of Mr. Von Osten. He taught the horse to answer Qs about content/numbers. The horse answered by tapping his hoof. Horse could only answer correctly if the person asking knew the answer. The horse started tapping and stopped from the subtle cues e.g. relaxation of face.
#11 The Machiavellian hypothesis of the evolution of intelligence
Their natural world does not require much innovation / technology. Maybe, the social problems that drove the development. Neocortex ratio relative to group size indicates that social intelligence is the prime mover. More brain power to deal with more individuals in the same group.
#11 The Machiavellian hypothesis of the evolution of intelligence: evidence
#1 Each individual knows about each individual and their relationships with each other. They established relationship with each other by grooming (social function), time spent on grooming predict how they support each other.
#2 There are social hierarchies, more than a pack of them; they form alliances, cooperate and help each other. Complexity of social life underestimated.
e.g. Alarm calls of infant were recorded and played, the other looks at the mother. Keep track of 3rd party relationships. larger group, need more capacity to keep track of them. Tactical deception. grooms behind the rock, doesn't get beat by alpha male.
#11 Mirror Self-recognition
Gordon Gallup (1970) more than casual observation. When they're sleep, put a mark on their face. Can only see from mirror. Chimp recognised and tried to remove the mark. "The surprise-mark test". Human children typically pass the test around 18 months (half) / 24 months. Monkey consistently failed, great apes (Chimps, gorilla, orangutans) succeeded.
#11 Phylogenetic tree / reconstruction / homology > analogy
Common questions, is the same trait stemmed from a common ancestors? by homology. or independently evolved E.g. wings in birds and insects? Solving a problem by analogy. Basic analysis to look at psychological capacities as well; evolution parsimony: simpler to say there's a common ancestor to explain for the secondary representation ability.
#12 Explain the special characteristics of human language
#12 Describe the hierarchies of linguistic components
#12 Explain the McGurk effect
#12 Identify violations of Gricean maxims
#12 Name brain areas associated with language
#12 Provide reasons for the idea of a language instinct
Speech Perception
We hear sounds according to how we produce them.
The McGurk Effect
Having an auditory noise that is different to the visual lip movement will make the perception of what we "hear" to be completely different. E.g. Auditory: /ba/; Visual /ga/ = Perception of /da/.
*This can also work for long sentences.
*This also works for visual input.
Chomsky's Universal Grammar
Languages differ in surface structure, and underlying rules share many elements. Eg. SOV (Japanese) vs. SVO (English).
Stages of Learning to Speak
8 Months: Practice pronouncing phonemes- babbling
10-15 Months: Real words appear
18-24 Months: Rapid word acquisition- 1 word every 2 hours- 2 word sentences
2-4 years: Syntax Acquisition
Overextention
Believing that one word means a whole lot of words. E.g. shoe> shoes; foot> foots
Bilingualism
Children at 2 years can easily differentiate between two languages they've been learning.
Gestural Language
Gestures accompany speech to convey analogue or additional information. Sign language is now recognized as a fully syntactic, natural language.
What is some experimental evidence that animals have a consciousness?
Colpaert et al (1980): normal rats prefer sugar
water over water containing analgesic. Rats with
chronologically inflamed joints (which is painful in
humans) prefer water containing analgesic
Humans and Chimpanzees
We share 99.4% of DNA with chimpanzees. We aren't descended from them though, we merely share a common ancestor.
Lloyd Morgan's Canon- The Principle of Parsimony
We should attribute animal behaviour to simplest explanation.
The Clever Hans Phenomenon
We may unknowingly give animals cues that will help them complete a required task.
The Machiavellian Hypothesis
Social intelligence as the prime mover.
The association between neocortex ratio and group size.
Primate Social Intelligence
Group Living.
Grooming.
Social hierarchies.
Keeping track of third party relations.
Tactical deception.