Mental chronometry

From Wikipedia, the free encyclopedia

Mental chronometry can be defined as the study of the temporal sequencing of information processing in the human brain, or as a precise measurement of psychological processes. Mental chronometric tasks have been used extensively in cognitive psychology and behavioral neuroscience to elucidate mechanisms underlying cognitive processing.

[edit] History

Psychologists have investigated mental chronometry for over 100 years. Mental chronometry is based on early studies in reaction time conducted by Franciscus Donders (1868).

[edit] Donders' experiment

Donders (1868’s): method of subtraction. Picture from the ‘Historical Introduction to Cognitive Psychology’ webpage.

Donders conducted experiments using reaction time tasks. Donders' work attempts to describe the processes going on in the mind, by analyzing cognitive activity into separate stages. Until Donder's work, many scientists had assumed that the mental operations involved in responding to a stimulus occurred instantaneously. Donders was particularly interested in "timing the mind" and used a subtraction technique to time the different mental processes that the brain goes through when faced with different tasks.

Donders performed experiments using reaction time tasks in 1868. His was the first attempt to analyze and measure the component processes of a simple task.
He used three tasks:

1. A simple reaction time task. For example, you are seated in front of a panel that contains a light bulb and a response button. When the light comes on, you must press the button.
2. A discrimination reaction time task. For example, you are seated in front of a panel with 5 light bulbs and one response button. When the target light goes on you must press the button, but not if the 4 other lights come on.
3. A choice reaction time task. For example, you are seated in front of 5 light bulbs, each with their own button. You must press the button corresponding to the appropriate light.

Donders then predicted the kinds of processes that might be involved in each task:

1. A simple time task would require perception and motor stages - time to receive and then execute the stimulus.
2. A discrimination reaction time task requires the above + a discrimination stage.
3. A choice reaction time task requires all of the above - time to receive and execute the stimulus, and discriminate + a choice stage.

As expected, simple tasks take the shortest amount of time, followed by discrimination tasks, with choice tasks taking the longest amount of time. Donders calculated the time required for each stage by using a subtraction technique:

1. Perception and motor time = time required for simple task
2. Discrimination time = time for discrimination task - simple task
3. Choice time = time for choice task - discrimination time.

This demonstrated a simple conclusion: more stages should require more time.

[edit] Application of mental chronometry in cognitive psychology

[edit] Posner’s letter matching studies

Posner (1978) used a series of letter-matching studies to measure the mental processing time of several tasks associated with recognition of a pair of letters. The simplest task was the physical match task, in which subjects were shown a pair of letters and had to identify whether the two letters were physically identical or not. The next task was the name match task where subjects had to identify whether two letters had the same name. The task involving the most cognitive processes was the rule match task in which subjects had to determine whether the two letters presented both were vowels or not vowels. The physical match task was the most simple because mentally subjects had to encode the letters, compare them to each other, and make a decision. When doing the name match task subjects were forced to add a cognitive step before making a decision. They had to search memory for the names of the letters, and then compare those before deciding. In the rule based task they had to also categorize the letters as either vowels or consonants before making their choice. The time taken to perform the rule match task was longer than the name match task which was longer than the physical match task. Using the subtraction method experimenters were able to determine the approximate amount of time that it took for subjects to perform each of the cognitive processes associated with each of these tasks.

[edit] Sternberg’s memory-scanning tasks

Sternberg (1966) devised an experiment wherein subjects were told to remember a set of unique digits in short-term memory. Subjects were then given a probe stimulus in the form of a digit from 0-9. The subject then answered as quickly as possible whether the probe was in the previous set of digits or not. The size of the initial set of digits was the independent variable and the reaction time of the subject was the dependent variable. The idea is that as the size of the set of digits increases the number of processes that need to be completed before a decision can be made increases as well. So if the subject has 4 items in short-term memory (STM), then after encoding the information obtained from the probe stimulus the subject will need to compare the probe to each of the 4 items in memory and then make a decision. If there were only 2 items in the initial set of digits then the number of processes would be reduced by 2. The data from this study found that for each additional item added to the set of digits that the subject had in STM about 38 milliseconds were added to the response time of the subject. This finding supported the idea that a subject did a serial exhaustive search through memory rather than a serial self-terminating search.

[edit] Cooper and Shepard’s mental rotation task

In Cooper and Shepard’s (1973) mental rotation task the subjects were presented with a letter or number that was either normal or backward. The stimulus was presented either upright or at angles of rotation in units of 60 degrees. The subject had to identify which type of stimulus it was: normal of backward. The subject had to encode the stimulus, then mentally rotate it until it became upright in the subject’s memory at which point it could be determined whether the image was normal or a mirror image of itself and a decision was made. If this is true then the more the subject has to rotate the stimulus to get it upright in STM the longer the response should take. The data bears this theory out as it shows the response time increase from 0 degrees until 180 degrees, but then begins falling again until it reaches 360 degrees. This shows that the subjects naturally rotate the image the shortest amount to get it upright again, rather than always going clockwise or counterclockwise. Metzler and Shepard (1974) also did a study involving three-dimensional objects. The subject was given two three-dimensional figures and had to determine whether or not they were the same. The data from this study also indicated that as the necessary rotation to make a decision increased so did the subject’s reaction time.

[edit] Sentence-picture verification

Mental chronometry has been a useful tool in identifying some of the processes associated with understanding a sentence. This type of research typically revolves around the differences in processing 4 types of sentences: true affirmative (TA), false affirmative (FA), false negative (FN), and true negative (TN). A picture can be presented with an associated sentence that falls into one of these 4 categories. The subject then decides if the sentence matches the picture or does not. The type of sentence determines how many processes need to be performed before a decision can be made. According to the data from Clark and Chase (1972) and Just and Carpenter (1971), the TA sentences are the simplest and take the least time, then FA, FN, and TN sentences.

[edit] Mental chronometry and models of memory

Hierarchical network models of memory were largely discarded due to some findings related to mental chronometry. The TLC model proposed by Collins and Quillian (1969) had a hierarchical structure indicating that recall speed in memory should be based on the number of levels in memory traversed in order to find the necessary information. But the experimental results did not agree with this model. For example, a subject will reliably answer that a robin is a bird more quickly than he will answer that an ostrich is a bird despite these questions accessing the same two levels in memory. This led to the development of spreading activation models of memory wherein links in memory are not organized hierarchically but by importance instead.

[edit] Application of mental chronometry in neuroscience

Regions of the Brain Involved in a Number Comparison Task Derived from EEG and fMRI Studies. The regions represented correspond to those showing effects of notation used for the numbers (pink and hatched), distance from the test number (orange), choice of hand (red), and errors (purple). Picture from the article: ‘Timing the Brain: Mental Chronometry as a Tool in Neuroscience’.

One can study the temporal characteristics of the way of where and how the brain is activated during activity by applying mental chronometry to functional imaging techniques. Mental chronometry tasks have become even more popular in the field of neuroscience in recent years. The way that mental chronometry is utilized is by performing tasks based on reaction time which measures through neuroimaging the parts of the brain which are involved in the cognitive processes.

Much research is being done now using mental chronometry and connecting it with cognitive studies however, there was extensive research being conducted in the past.

First, in the 1950’s, the use of a micro electrode recording of single neurons in anaesthetized monkeys allowed research to look at physiological process in the brain and supported this idea that people encode information serially.

In the 1960s, these methods were used extensively in humans: researchers recorded the electrical potentials in human brain using scalp electrodes while a reaction tasks was being conducted using digital computers. What they found was that there was a connection between the observed electrical potentials with motor and sensory stages for information processing. For example, researchers found in the recorded scalp potentials that the frontal cortex was being activated in association with motor activity. These finding can be connected to Donders’ idea of the subtractive method of the sensory and motor stages involved in reaction tasks.

Then, with the discovery of functional magnetic resonance imaging (fMRI), techniques were used to measure activity through electrical event-related potentials in a study when subjects were asked to identify if a digit that was presented was above or below five. According to Sternberg’s additive theory, each of the stages involved in performing this task includes: encoding, comparing against the stored representation for five, selecting a response, and then checking for error in the response. This fMRI image presents the specific locations where these stages are occurring in the brain while performing this simple mental chronometry task.

In the 1980s, neuroimaging experiments allowed researchers to detect the activity in localized brain areas by injecting radionuclides and using positron emission tomography (PET) to detect them. Also, fMRI was used which have detected the precise brain areas that are active during mental chronometry tasks. Many studies have shown that there is a small number of brain areas which are widely spread out which are involved in performing these cognitive tasks.

[edit] External links

• Historical Introduction to Cognitive Psychology
• Timing the Brain: Mental Chronometry as a Tool in Neuroscience
• Sample Chronometric Test on the web

[edit] References

• Clark, H. H., & Chase, W. G. (1972). On the process of comparing sentences against pictures. Cognitive Psychology, 3, 472-517.
• Collins, A. M. & Loftus, E. F. (1975). A spreading activation theory of semantic processing. Psychological Review, 82, 407-428.
• Collins, A. M. & Quillian, M. R. (1969). Retrieval time from semantic memory. Journal of Verbal Learning and Verbal Behavior, 8, 240-247.
• Cooper, L. A., & Shepard, R. N. (1973). Chronometric studies of the rotation of mental images. New York: Academic Press.
• Just, M. A., & Carpenter, P. A. (1971). Comprehension of negation with quantification. Journal of Verbal Learning and Verbal Behavior, 10, 244-253.
• Mayer, R. E. (1992). Thinking, Problem Solving, Cognition. New York: W. H. Freeman and Company.
• Metzler, J., & Shepard, R. N. (1974). Transformational studies of the internal representation of three-dimensional objects. Hillsdale, NJ: Erlbaum.
• Posner, M. I. (1978). Chronometric explorations of mind. Hillsdale, NJ: Erlbaum, 1978.
• Posner, M. I., & Mitchell, R. F. (1967). Chronometric analysis of classification. Psychological Review, 74, 392-409.
• Sternberg, S. (1966). High speed scanning in human memory. Science, 153, 652-654.
• Sternberg, S. (1969). The discovery of processing stages: Extensions of Donders' method. Acta Psychologica, 30, 276-315.
• Sternberg, S. (1975). Memory scanning: New findings and current controversies. Quarterly Journal of Experimental Psychology, 27, 1-32.
• ‘Canadian Society for Brain, Behaviour and Cognitive Science’ webpage.