Experimental Psychology PSY 433

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Experimental PsychologyPSY 433

• Chapter 8
• Attention and Reaction Time

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How Attention Guides Learning
You remember later whatever you paid sufficient
attention to
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Change Blindness Demo

• http//viscog.beckman.illinois.edu/flashmovie/23.p
  hp

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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.

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Speed-Accuracy Tradeoff
Psychological refractory period here
SOA (S1-S2 Interval in ms)
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Stress and Cognitive Control

• Two possible effects of stress on cognition
• Stress requires attention (capacity) thus
  decreasing performance.
• People adapt to stress by finding more efficient
  ways of doing tasks increasing performance
  (strategies change).
• Steinhausers experiment
• Long/short interval cues to respond to digit or
  letter 6M
• Is letter a consonant/vowel, is digit odd/even?

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Results

• For the low stress condition there was an
  interaction between stimulus interval and task
  repetition (same task next or different next).
• No interaction in the high stress condition.
• Under low stress there was a relatively higher
  cost to changing tasks quickly.
• Under high stress the cost was the same.
• This is consistent with the idea that under
  stress cognitive strategies change.

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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.

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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).

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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.

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Stress and Cognitive Control

• Two possible effects of stress on cognition
• Stress requires attention (capacity) thus
  decreasing performance.
• People adapt to stress by finding more efficient
  ways of doing tasks increasing performance
  (strategies change).
• Steinhausers experiment
• Long/short interval cues to respond to digit or
  letter 6M
• Is letter a consonant/vowel, is digit odd/even?

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Automaticity

• Practice reduces the need for attention by
  reducing central cognition, making a task
  automatic.
• Practice enables parallel processing.
• Spelkes 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.

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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

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Stroop Demo
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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.

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Lateralized Stroop Task (Lab)
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Excel Results
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ANOVA Results (Clean Data)
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Interpreting the Results

• There was a significant main effect of
  congruence, F(1,16)42.033, p.000.
• No other significant main effects or interactions
  were found.
• Although it was hypothesized that presentation of
  stimuli to the right visual field might result in
  greater interference, no significant differences
  between right and left presentation were found.
  However there was a slight trend toward longer RT
  to the right.

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Goals of the Final Report

• Communicate to the scientific community.
• Clearly describe your project in sufficient
  detail to permit replication.
• Convince readers that your findings support your
  conclusions.
• How strong is the evidence?
• Does it justify your statements about theory?
• Summarize your contribution to the ongoing debate
  on an important question.
• Pay special attention to your abstract!

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Contents of Final Report

• Must contain all sections listed in the APA
  Publication Manual, including
• Title page
• Abstract
• Introduction
• Methods
• Results
• Discussion
• References
• Tables and Figures

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You Are Telling a Story

• Introduction -- state your research question,
  review the literature, make your predictions
  (hypotheses).
• Methods describe how you explored the question
  in sufficient detail to permit replication.
• Results describe your findings and test your
  hypotheses using statistics.
• Discussion analyze your results and put them
  back into the context of your question.

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Abstract

• This may be the only part of your paper that most
  people read, so make it count!
• Write this last.
• Tell the story of your study, with one sentence
  per report section.
• Do not exceed 120 words.

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Use of Tenses

• For the final report, revise sections of your
  proposal because they will be graded again.
• Your proposal was written in the future tense
  (e.g., subjects will), but
• Put the Methods section in the past tense.
• Report your results in the past tense.
• Tense varies in the Introduction and Discussion.

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Reporting Results

• Only include the results that are relevant to
  your research question, not all data collected.
• Go from the general to the specific.
• Provide tables for
• Multiple analyses.
• Complex experiments (factorial designs).
• ANOVA
• Organize your results section around your
  hypotheses, testing one at a time.

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Describing Data

• Give both descriptive and inferential statistics.
• The mean number of words recalled was calculated
  for each group. The means and the standard
  deviations for each group are shown in Figure 1.
• Recall was higher for the drug group (M 15, SD
  5.43) than for the placebo group (M 10, SD
  4.98).

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Reporting Statistics

• The data were analyzed using an independent
  t-test. The t-test showed no significant
  difference between the mean of the placebo group
  and the mean of the drug group, t(34) 1.35, p lt
  .05.
• Using two-way ANOVA, the main effect of gender
  was found to be significant, with females scoring
  higher on the average than males, F(1, 23)
  23.89, p lt .05.
• Better to show this analysis in a table.

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References

• Format varies depending on the type of material
  being referenced (e.g., book, article, web site).
• Only list the sources actually mentioned in the
  text of your report.
• Everything listed in the references must be cited
  in text
• Everything cited in text must be listed in the
  references.
• When you mention a source referenced in another
  paper say as cited in and cite the source you
  actually read, not the original.

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Tables and Figures

• Tables go first always use APA format.
• Figures are camera-ready original artwork that
  will be used by the publisher as is.
• Do not put page numbers, headers, figure captions
  or anything else on the front of the figure.
• Lightly write the figure number and short title
  on the BACK of each figure.
• Put all figure captions in a single list that
  appears before the figures.

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Discussion

• First, state what you discovered during your
  experiment.
• Do not repeat results but state them in terms of
  the larger construct theory being tested.
• Tell whether your findings are consistent with
  what others have found.
• Describe any threats to validity and problems
  with your experiment (confounds, bias,
  limitations of generalizability, problems).
• Conclusion what are the consequences?