Lab 2: Limited Processing Capacity

Perhaps the most fundamental concept implied by an information-processing model of skill performance is that of a limited capacity processor. The analogy in computer language is the size of the Random Access Memory (RAM) in your computer. The size is usually measured in mega bytes (e.g., your computer might have 256 MB of processing capacity). When this capacity is translated into performance, this refers to the number of tasks that your computer can maintain in an active state. For example, your computer could be controlling the printing of a document in MS Word, while you are searching for things on the Internet. In this lab we will see how easy/difficult it is for humans to control more than one task at a time.

The research hypothesis for this lab is that a person will be able to count backwards at a faster rate while sitting in a chair than while balancing on one foot. That is, the processing capacity required to balance in a chair is less than for balancing on one foot. Processing capacity is discussed in the text on pages 72-80.

Methodology

Participant

A single participant between the ages of 18 and 25 years will perform under four test conditions: a) balancing on one foot, b) balancing on one foot on a can of soup, c) balancing on one foot on a can of soup while blindfolded, d) control (standing on two feet). People who have had extensive practice with balancing skills (e.g., a gymnast) should not be used as participants.

Equipment/Material

The equipment includes a blindfold (that totally blocks central and peripheral vision) and an ordinary can of soup (approximately 6.5 cm in diameter and 10 cm in height). The experimenter will use a stopwatch to time the trials. It will be necessary to have two experimenters: one experimenter as a spotter to ensure the person does not fall and to time the trial and a second experimenter to initiate and then monitor the counting.

Procedure

The primary task to be performed by the participant is balancing on one foot (participant may choose the foot, but it must be the same foot for all trials). The secondary task (to be performed while balancing) is counting backwards by 7s from a number between 200 and 300 chosen randomly by the experimenter on each trial.

On a single trial the participant will begin balancing/sitting. As soon as the participant has successively gained their balance (approximately 5s), the experimenter will “call-out” a number between 200 and 300 (e.g., 153). While maintaining balance the participant will begin counting backwards by 7s towards zero as quickly as possible. Ideally the participant will remain balanced for 60s. However, a trial stops if the participant loses their balance and touches the floor with the other foot or grasps onto something with one of their hands. Any trial lasting less than 40s is to be redone. At the end of a trial the experimenter records the number of backward-counting steps completed (e.g., at beginning experimenter calls out “233” and participant then counts “226”, “219”, “212”, “205”, “198” = 5 steps). This number is then divided by the exact time for the trial (normally this will be 60s). For example, 5 steps divided by 60s = 0.08 counting steps per second.

In the control condition, the participant stands comfortably on two feet, hands at the sides. After hearing the starting number presented by the experimenter, the participant counts backwards by 7s as quickly as possible for 60s. The participant completes two trials (remember, each trial must begin with a different starting number). If the performer makes more than two counting errors the trial must be redone. A counting error occurs if the participant does not correctly subtract 7 from the previous number spoken.

The one foot balancing conditions are run in the same manner as the control, with the performer ultimately completing two successful trials in each condition (i.e., balance maintained for more than 40s and two or less counting errors committed). The performer is allowed to use the arms to assist with balance. Participants are allowed sufficient practice to be comfortable with the primary task before beginning the experimental trials. The participant shifts to a new test condition after the completion of each successful trial. The order of testing should be a), b), c), d), d), c), b), a).

Dependent variable

The assumption made in this primary/secondary task methodology is that the performer is executing the primary task to the best of their ability (i.e., the performer is allocating the necessary processing capacity just as would happen if the primary task was being performed alone). This means that performance on the secondary task is a measure of spare capacity (see Fig. 3.7 in text). In this case the slower the counting (small counting rate as measured in steps/second) the greater the processing capacity required to perform the primary task.

For each condition, the average counting rate (counting steps per second) is computed. To determine the processing capacity required for each balance task, the counting rate for the control condition is compared to the balance condition. The larger the difference between the control, counting rate and the balance-condition rate, the larger the required capacity for that balancing task (see green vs. white shaded areas in Fig. 3.7).

Results

Using a pictorial display something like that used in Fig. 3.7, display the processing requirements of the four test conditions. In the secondary task segment of each picture record the average counting rate (steps/s).

Discussion

  1. Briefly present why you think the processing capacity required to control balancing while blindfolded should have been highest (and therefore counting performance worst), followed by c), followed by b), with the control condition easiest. Did your results conform to this?
  2. Explain why “stimulus identification” would not likely play a role in determining your results.

Writing your lab

REMEMBER THAT YOUR WRITING SHOULD BE AS PERFECT AS YOU CAN MAKE IT. If you write poorly find an editor. In science poor grammar, unclear sentences, and poor writing style are not tolerated. While no grades are assigned directly for writing, it is unavoidable that labs that are well written will likely receive higher grades than labs written poorly, because the former will be much easier to understand. IT IS NOT THE MARKER’S JOB TO TRY TO FIGURE OUT WHAT THEY THINK THE WRITER MEANT IN POORLY WRITTEN MATERIAL.

Form for write-up

  1. Maximum word count for report is 300 words.
  2. On top right (as a header) put your name, student number, and word count.
  3. Your report will have the following parts:
  • title (centred at top of page)
  • 2-3 sentences as introduction including your research hypothesis (what you think will happen.
  • results section (titled and centred “Results”) – ideally a computer generated picture of the results – 1-2 sentence explanation of picture if deemed necessary.
  • discussion section (titled and centred “Discussion”) – number your answers to the questions (see above).

Marks

  1. Overall presentation of paper 20%
  2. Results (accuracy & presentation/clarity of picture)30%
  3. Question one 30%
  4. Question two 20%