Choice Response Task
- Several stimuli w/ a response for each
- Respond as quickly as possible
- Uncertainty increases w/ number of alternatives, with each BIT of information reducing uncertainty by half.
- Total info transmitted is the reduction in uncertainty
Information Theory
- Communication Channel
- Bits as binary signal
- Quantifying messages as bits
In Information Theory, low probability events provide more/ less information?
MORE
Varying stimulus probability task
- 4 possible stimuli with varying probability
- low probability stimulus with signal more information, leading to a SLOWER response
Mind as a Communication Channel
- Abstract model
- metaphor for mechanism
- Quantifying processing properties
Possible arrangements of mental operations (3)
- Continuous Activation
- Stage Activation (works for some situations, good starting pt.)
- Cascaded Activation
The idea that mental events occur in sequence and that the total time for a task is the sum of the time for each event.
Mental Chronometry
Subtractive Method (Donders)
- If A+B=8s, and B=5s, A must = 3s
- requires theory to analyze event organization
Posner’s Letter Matching Task
- Decide if 2 letters are the same or different
- Letters can be physically identical (PI) or have the same name (NI, as in A a).
- “Same” responses found to be faster for PI.
Steps in the Stage Analysis of Letter Matching (Posner’s Letter Matching Task)
- Encode stimuli
- Compare physical codes
- Retrieve name codes
- Compare name codes
NI (Posner’s letter matching task) correlates with…
Reading skill, information processing tasks.
->possible index of memory across time.
2 critical assumptions of Subtraction
- Non-overlapping stages (NOT CASCADED ACTIVATION)
2. Pure insertion
Rate Measurement
Uses the logic of subtraction and suggests that instead of using additional stages, we add more of something. It is thus less likely that this changes the nature of the task, and more likely that pure insertion is correct.
Rate Measurement in Visual Search
- Present an array of items
- Search for a target
- Respond as soon as target is found (BETTER= respond “present” or “absent” (y/n)
2 Assumptions of Rate Measurement
- Pure insertion (quite likely)
2. Nonoverlapping stages (usually confirmed by linear function)
Describe the slopes of “present” vs. “absent” trials for the Visual Search task.
- On average, only half of the items need to be considered on “present” trials, although p/a processes are similar.
- Slopes for “present” are typically half as great as “absent” trials
Function of information processing tasks?
- Measure duration of unobservable events
- Provide evidence on the arrangement of stages
- Uncover general principles of mental events (effects of uncertainty, time for memory access, sequential search processes
