| Mental Chronometry |
Article Index for Mental |
Website Links For Mental |
Information AboutMental Chronometry |
| CATEGORIES ABOUT MENTAL CHRONOMETRY | |
| cognition | |
|
Psychologist s have investigated mental chronometry for over 100 years. 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. Mental chronometry is based on early studies in Reaction Time conducted by Donders (1868). MAJOR RESEARCH FINDINGS Posner’s letter matching studies Posner 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. Sternberg’s Memory-Scanning Tasks Sternberg 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. Cooper and Shepard’s Mental Rotation Task In Cooper and Shepard’s 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 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. 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. 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 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. McClelland’s Cascade Model (1979) Deals with an idea counter to Stenberg’s – which the processes do not occur serially, but can activate, in parallel. APPLICATION OF MENTAL CHRONOMETRY IN NEUROSCIENCE |
|
|