Lecture 8:
Human Cognition
Logistics
• Homework-1 is up, due on Sunday.
• All slides until last week + reading resources are up.
• Please do catch up with your readings.
• Next quiz on Friday the 14th Feb (covering basics of humans).
• Mid-sem exam scheduled
• 01 March 2025 (Sat); 8:00-10:00 am; Location:TBA
Recap
• Humans as processors
• Inputs → Senses
• Vision, Hearing, Touch
• Outputs
• Motor, speech, brain signals, biomarkers, gaze/emotions
• Today: Processing
• Attention, memory, learning, decision making, problem solving
• Motivation, emotions, behaviors
• All the things that comprise “mind”
Attention
• Perceptual memory stores whatever we perceive
• Attention is the ability to actively process the perceived stimuli
• Limited resource: we selectively “attend to” some stimuli, exclude others
• So, what do we pay attention to?
• Top-down / endogenous: affected by internal state, task goals, decision to make, etc.
• Bottom-up / exogenous: From external environment, based on “saliency” (e.g., surprise,
biases/interests) [non-salient are ignored]
• When the latter gets in the way of former, distractions happen
• Getting attention back after a distraction takes time, can also be disastrous
• Multi-tasking does not necessarily work (Attention is divided; errors go up)
• Some people have impaired attention (ADD/ADHD)
Attention in HCI
• Limited resource
• Interfaces need to draw attention to the right things
• E.g., what is different / unique draws attention
• Too much clutter → compete for attention, hard to focus
• Help decide quickly where to pay attention
• Minimize distractions
• Clippy, chatbots that annoy, pop-up windows
• Marquee, moving text, etc.
• People overlook too much irrelevant stuff as “noise”
• Useful stuff might be ignored
• Attention diffuses; need to keep people alert/engaged
Memory
• Process/ability to store and retrieve information
Sensory buffers /
perceptual memory
Human memory Short-term memory
Implicit / Procedural
Episodic
Long-term memory
(events, experiences)
Explicit
Semantic (facts)
Short-term memory
• Let’s play a game: remember the following sequence of digits
• Write it down now
9733015217
Short-term memory
• Now remember this (do not write down)
• FHIDDTASRRVHA
• Check the previous one: 9733015217
• Now write down the letters you memorized!
Short-term memory
• Faster to remember, faster to recollect
• Short lived: 15-30 seconds, provided no distractions
• Small capacity: 7+/2 items or “chunks”
• How many of you remembered digits broken down into parts?
• Also why mnemonics work
• What goes into short-term memory: everything!
• Important to remember what you’re working on, goals, options for
comparisons, intermediate results, etc.
Short-term memory implications for HCI
• Don’t make people remember (e.g., one screen to another)
• Copy-paste is made for exactly this purpose!
• Show options, intermediate stages, etc.
• Allow for “closure” → people forget to put some tasks to short-
term memory for completion
• E.g., take card after ATM withdrawal (closure happen when cash is
withdrawn)
• Most ATMs give back card before cash, for this reason!
Long-term memory (LTM)
• Lifelong (mostly)
• Stuff from STM goes to LTM by “Rehearsal” / repetition
• More the repetition, the better/longer we remember
• Distribution of “rehearsal”
• Not cramming, but periodically rehearsing/repeating
• 10 min a day is better than 2 hours over a weekend
What goes into LTM?
• Procedural / habitual / how to do things
• “Muscle memory”
• Doesn’t need conscious attention (walk absentmindedly, ride a cycle)
• Flawed, attention is not in use and errors happen
• Episodic memory
• Events, experiences
• Serial in nature
• Semantic memory
• Facts, concepts, etc.
• Thought to be an interconnected graph (also as frames, sometimes!)
• Which is thinking of one reminds us of others!
• All these parts are also interconnected!
Limitations of LTM
• Long to learn and store
• Long to retrieve (sometimes we need to reconstruct, go through
sequence of nodes to get to what we need)
• Flawed
• We forget stuff [decay, interference]
• Retrieval takes time
• Biased (recency, frequency, saliency, emotional responses)
• Old habits (old year, instead of new year)
Implications for HCI
• Recognition over recall
• Provide memory aids (DON’T EXPECT USER TO REMEMBER!)
• Trainings also don’t work for the same reason!
• Use of conventions/standards → use rehearsed memory
• Humans are creations of habit
• Don’t change interfaces, if need be, account for its error proneness
• Over time, people can memorize things
• Allow for shortcuts that are quicker
Thinking: reasoning & problem solving
• Now that stuff is in memory, can be used
• Reasoning → derive new “insights” from prior knowledge
• Deductive reasoning (deduce from facts)
• If Tuesday, then class. Today is Tuesday. There is class.
• If Tuesday, then class. Tomorrow is Wednesday. Is there class tomorrow?
• Inductive reasoning
• Generalizations from seen instances to unseen instances
• Useful: Helps fill gaps, guess what to expect, etc.
• Abductive reasoning
• Assigning causes for why something happened
• We are horrible at this (so, don’t leave gulf of evaluation!)
What this means for HCI?
• Reasoning is information heavy
• Prone to confusion and fallacies
• Computers are very good at this stuff
• There’s a lot of scope for computers to support humans on this
• Information heavy, computers can also help there
• When people don’t know an interface:
• They try to “reason” their way out, “guess” (make inferences), etc.
• Do not allow for that – humans are horrible at it!!!
Next class
• Problem solving
• Learning
• Motivation
• Emotions
• Then, human errors
Readings:
• “Attention and its implication for HCI”, Claudia Roda
• Finish Dix, Chapter on “Humans”
