Speed Accuracy
In general, rushing someone to finish a task results in worse accuracy compared to letting them finish without hurrying. Put another way, increasing speed pressure decreases accuracy, while increasing attention to accuracy decreases speed. This is called the speed-accuracy tradeoff and there are few exceptions to this rule. A real-world example is typing. If you try to type fast you will make more mistakes than if you slow down and try to type perfectly. Some tasks like swinging an axe can be completed better only at faster speeds but that is one of a few exceptions to the rule.
The speed-accuracy tradeoff is of particular concern for cognitive psychologists because if some experimental participants emphasize speed and not accuracy, they will produce different results from those who emphasize accuracy and not speed. Statistical results obtained from participants at two opposite ends of the spectrum can be misleading, and researchers must take steps like excluding trials with incorrect responses or limiting the time window allowed to make a response during the experiment.
Focus on Speed or Accuracy
In this lab activity, you will be able to observe the consequences of putting your focus on either speed or accuracy or balancing between them during a simple letter detection experiment. The experiment contains three segments where you will focus on either speed, accuracy, or a balance between the two. On each of 72 trials you will be presented with one to three letters. You will be asked to identify if there is an “O” (press “O” key) or a “T” (press “T” key) within the string of letters. After you respond you will be given feedback about whether you responded too fast or too slow and whether your response was correct or incorrect. Then you will see a fixation screen and can press the spacebar to begin the next trial.
Difficulty as a Function of Speed and Accuracy
In addition to varying speed and accuracy pressure, some trials are easier, while some are harder. Trials where the letter is easy to spot include when “OX” is presented. The letter is harder to spot in “OQ” given the relative similarity between “O” and “Q” compared to “X”. When presented with results after you complete the trials, the top graph shows response times, while the bottom graph shows accuracy.
You can see the speed-accuracy tradeoff by looking at the response times and the accuracy together. During the speed pressure trials, the speed-accuracy tradeoff is shown by fast response times and poor accuracy. During the accuracy pressure trials, slower response times correspond to higher accuracy. The balance condition shows response times and accuracy that fall in between speed pressure and accuracy pressure trials. The impact of instructions on speed-accuracy tradeoffs is demonstrated by comparing the hard and easy conditions in the speed pressure and accuracy pressure blocks. During speed pressure trials, there is a significant difference between easy and hard. In the accuracy pressure trials, there is no significant difference between easy and hard.
Experimenter Considerations
An experimenter who wanted to know if there was a difference in processing time needed for easy and hard trials would obtain a different answer depending on whether participants were instructed to emphasize speed or accuracy. This means that whenever response time results are considered, accuracy results must also be considered. Fast trials that are accompanied by significant increases in error rates indicate a speed-accuracy tradeoff. The importance of this lab demonstration is that during cognitive tasks significant differences between groups may or may not be observed depending on the priorities between speed and accuracy set by the participant. Results can be inconsistent from participant to participant, making it difficult to determine which effects are real and which are due to participants’ decision to be either fast or careful.