Experimental Psychology PSY 433 Chapter 8 Attention and Reaction Time

How Attention Guides Learning Motivation What is your goal? What do you care about? What are you interested in? Selective Attention to Environment You remember later whatever you paid sufficient attention to

Change Blindness Demo http://viscog.beckman.illinois.edu/flashmovie/23.php

Learn by Doing When you try something yourself instead of listening to someone tell you what to do, your attention shifts to different aspects of task. Doing shows you what you need to know – what questions to ask. However, “doing” without instruction requires trial & error which can be wasteful & time-consuming. Following instructions without paying attention to them is also wasteful – no learning occurs.

Dependent Variables Reaction time is the preferred DV. Percentage of correct responses. Derived statistics such as: d’ (d prime) – the difference between signal detection and guessing. Beta – criterion for decision processes Rate of performance (d’/sec, bits/sec) Voltage change and pattern in EEG and ERP studies. Various types of imaging.

Independent Variables Decision making: Number of alternatives in a choice Number of decisions to be made to identify the correct stimulus and associated response. Presentation rate Complexity of a task. Task demands -- overload of information. For ERP studies, recording site is a quasi-independent variable (selected not manipulated).

Control Variables Changes in reaction time are small so experiments require precise control. Perceptual factors, such as intensity and duration of stimuli are typically controlled by computer. In EEG & ERP studies, sophisticated recording equipment is needed to filter out extraneous electrical activity.

Automaticity Practice reduces the need for attention by reducing central cognition, making a task automatic. Practice enables parallel processing. Spelke’s two tasks: Read text for comprehension Write down words read by an experimenter After 6 weeks subjects could read at normal speed and answer questions.

Stroop Effect Color words were presented printed in different ink colors. Control stimuli were non-color words in different inks or color bars (not words) Subjects were asked to name the ink color as quickly as possible. Demo

Stroop Demo

Why it Happens Automatic processes are difficult to stop. It is nearly impossible to look at a word without reading it. Neutral words name non-colors so ink can be named without interference. Color words that conflict with ink color take longer because reading the word cannot be inhibited.

Lateralized Stroop Task (Lab)

Excel Results

ANOVA Results (Clean Data)

APA Format ANOVA Table Sum of Squares df Mean Square F sig Congruent .298 1 42.033 .000 Error (Congruent) .113 16 .007 Location .021 2 .011 1.304 .286 Error (Location) .260 32 .008 Congruent*Location .005 .003 .294 .747 Error (Congruent* Location) .285 .009