PSYCH 240 LEC 6 (PATTERN RECOGNITION: TOP-DOWN)

Top-Down Processing

• Originates in higher cognition + proceeds downward toward sensations

  • types

    • expectation/bias

    • context

    • higher levels of analysis that affect lower ones

Top

• Area of brain responsible for high-level cognition

  • goal setting

  • decision-making

Down

• Refers to lower-level area of brain that receive input from sensation

  • vision

  • audition

Signal detection theory

• Addresses how we make these detection decisions

• Demonstrates how expectation/bias (top-down influence) effect perception

Signal detection theory: signal

• Something in environment you are trying to detect

Signal detection theory: noise

• Things in environment other than the signal

Signal detection theory: sensitivity

• How easy/difficult it is to discriminate signal (beep) from noise

• How good detectors are

  • vision

  • hearing

  • sense of touch

Signal detection theory: bias

• Your bias/tendency to say

  • yes vs no

• Determined by expectations or payoffs

Signal detection theory: hits

• There is a signal present + correctly detect it

Signal detection theory: misses

• There is a signal present + fail to detect it

Signal detection theory: correct rejections

• There is no signal + correctly say there was no signal

Signal detection theory: false alarms

• There is no signal + you say there was a signal

Signal detection theory: bias/payoff effects.

• Participants lower threshold to have an increased chance of getting $10 in both experiences

• Use payoff to increase production of yes or no criterian threshold bias

Context effects

• when perceptions of an object is affected by its context/environment

  • Subjective contours

  • Letter recognition

Subjective contours

• Add 3 pac-man shapes and 3 angle brackets

  • In mind, they perceive triangles (not present)

• Neurons perceive the contours/edges as if they were present based on context

Word superiority effect (reicher)

• example of top-down effect

  • high-lvl (words) affect perception of lower-level (letters)

  • Superior at pattern recognition in words vs in letter form

pseudoword superiority effect

During a forced choice task

• They give 2 alternative choices

  • During this, there will be a non-word condition that is pronounceable, not real word

• Better than letter condition still

• Not as strong as real-word condition

interactive activation model (McClelland + Rumelhart of 1981)

• Two sources of input

  • bottom-up activation from features

  • top-bottom from the words

• Helps support the word superiority effect