# Mental chronometry

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Mental chronometry is the use of response time in perceptual-motor tasks to infer the content, duration, and temporal sequencing of cognitive operations. Mental chronometry is one of the core paradigms of experimental and cognitive psychology, and has found application in various disciplines including cognitive psychophysiology/cognitive neuroscience and behavioral neuroscience to elucidate mechanisms underlying cognitive processing.

Mental chronometry is studied using the measurements of reaction time (RT). Reaction time is the elapsed time between the presentation of a sensory stimulus and the subsequent behavioral response. In psychometric psychology it is considered to be an index of speed of processing.[1] That is, it indicates how fast the thinker can execute the mental operations needed by the task at hand. In turn, speed of processing is considered an index of processing efficiency. The behavioral response is typically a button press but can also be an eye movement, a vocal response, or some other observable behavior.

## TypesEdit

Response time is the sum of reaction time plus movement time.

Usually the focus in research is on reaction time. There are four basic means of measuring RT given different operational conditions during which a subject is to provide a desired response:

Simple reaction time is the time required for an observer to respond to the presence of a stimulus. For example, a subject might be asked to press a button as soon as a light or sound appears. Mean RT for college-age individuals is about 160 milliseconds to detect an auditory stimulus, and approximately 190 milliseconds to detect visual stimulus.[2]

Recognition or Go/No-Go reaction time tasks require that the subject press a button when one stimulus type appears and withhold a response when another stimulus type appears. For example, the subject may have to press the button when a green light appears and not respond when a blue light appears.

Choice reaction time (CRT) tasks require distinct responses for each possible class of stimulus. For example, the subject might be asked to press one button if a red light appears and a different button if a yellow light appears. The Jensen Box is an example of an instrument designed to measure choice reaction time.

Discrimination reaction time involves comparing pairs of simultaneously presented visual displays and then pressing one of two buttons according to which display appears brighter, longer, heavier, or greater in magnitude on some dimension of interest.

Due to momentary attentional lapses, there is a considerable amount of variability in an individual's response time, which does not tend to follow a normal (Gaussian) distribution. To control for this, researchers typically require a subject to perform multiple trials, from which a measure of the 'typical' response time can be calculated. Taking the mean of the raw response time is rarely an effective method of characterizing the typical response time, and alternative approaches (such as modeling the entire response time distribution) are often more appropriate.[3]

## The evolution of mental chronometry methodologyEdit

### Abū Rayhān al-BīrūnīEdit

Psychologists have developed and refined mental chronometry for over the past 100 years. The Persian scientist Abū Rayhān al-Bīrūnī was the first person to describe the concept of reaction time:

"Not only is every sensation attended this by a corresponding change localized in the sense-organ, which demands a certain time, but also, between the stimulation of the organ and consciousness of the perception an interval of time must elapse, corresponding to the transmission of stimulus for some distance along the nerves."[4]

### Galton and differential psychologyEdit

Sir Francis Galton is typically credited as the founder of differential psychology, which seeks to determine and explain the mental differences between individuals. He was the first to use rigorous reaction time tests with the express intention of determining averages and ranges of individual differences in mental and behavioral traits in humans. Galton hypothesized that differences in intelligence would be reflected in variation of sensory discrimination and speed of response to stimuli, and he built various machines to test different measures of this, including reaction time to visual and auditory stimuli. His tests involved a selection of over 10,000 men, women and children from the London public.[1]

### Donders' experimentEdit

The first scientist to measure reaction time in the laboratory was Franciscus Donders (1869). Donders found that simple reaction time is shorter than recognition reaction time, and that choice reaction time is longer than both.[2]

Donders also devised a subtraction method to analyze the time it took for mental operations to take place.[5] By subtracting simple reaction time from choice reaction time, for example, it is possible to calculate how much time is needed to make the connection.

This method provides a way to investigate the cognitive processes underlying simple perceptual-motor tasks, and formed the basis of subsequent developments.[5]

Although Donders' work paved the way for future research in mental chronometry tests, it was not without its drawbacks. Donders' insertion method was based on the assumption that inserting a particular complicating requirement into an RT paradigm would not affect the other components of the test. This assumption - that the incremental effect on RT was strictly additive - was not able to hold up to later experimental tests, which showed that the insertions were able to interact with other portions of the RT paradigm. Despite this, Donders' theories are still of scientific interest and his ideas are still being used in certain areas of psychology, which now have the statistical tools to use them more accurately.[1]

### Hick's LawEdit

Main article: Hick's Law

W. E. Hick (1952) devised a CRT experiment which presented a series of nine tests in which there are n equally possible choices. The experiment measured the subject's reaction time based on number of possible choices during any given trial. Hick showed that the individual's reaction time increased by a constant amount as a function of available choices, or the "uncertainty" involved in which reaction stimulus would appear next. Uncertainty is measured in "bits", which are defined as the quantity of information that reduces uncertainty by half in information theory. In Hick's experiment, the reaction time is found to be a function of the binary logarithm of the number of available choices (n). This phenomenon is called "Hick's Law" and is said to be a measure of the "rate of gain of information." The law is usually expressed by the formula $RT = a + b\log_2(n + 1)$, where $a$ and $b$ are constants representing the intercept and slope of the function, and $n$ is the number of alternatives.[6] The Jensen Box is a more recent application of Hick's Law.[1] Hick's Law has some interesting modern applications in marketing, where restaurant menus and web interfaces (among other things) take advantage of its principles in striving to achieve speed and ease of use for the consumer.[7]

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.[8] Sternberg (1969) developed a much-improved method for dividing reaction time into successive or serial stages, called the additive factor method.[9]

### Shepard and Metzler’s mental rotation taskEdit

Main article: Mental rotation

Shepard and Metzler (1971) presented a pair of three-dimensional shapes that were identical or mirror-image versions of one another. Reaction time to determine whether they were identical or not was a linear function of the angular difference between their orientation, whether in the picture plane or in depth. They concluded that the observers performed a constant-rate mental rotation to align the two objects so they could be compared.[10] Cooper and Shepard (1973) presented a letter or digit that was either normal or mirror-reversed, and 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 or mirror-reversed. Response time increased roughly linearly as the orientation of the letter deviated from upright (0 degrees) to inverted (180 degrees), and then decreases again until it reaches 360 degrees. The authors concluded that the subjects mentally rotate the image the shortest distance to upright, and then judge whether it is normal or mirror-reversed.[11]

### Sentence-picture verificationEdit

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, than FA, FN, and TN sentences.[12][13]

### Mental chronometry and models of memoryEdit

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 (e.g., Collins & Loftus, 1975), wherein links in memory are not organized hierarchically but by importance instead.[14][15]

## Mental chronometry and cognitive development Edit

Main article: Neo-Piagetian theories of cognitive development

In recent years there has been extensive research using mental chronometry methods for the study of cognitive development. Specifically, various measures of speed of processing were used to examine changes in the speed of information processing as a function of age. Kail (1991) showed that speed of processing increases exponentially from early childhood to early adulthood.[17] Studies of reaction times in young children of various ages are consistent with common observations of children engaged in activities not typically associated with chronometry.[1] This includes speed of counting, reaching for things, repeating words, and other developing vocal and motor skills that develop quickly in growing children.[18] Once reaching early maturity, there is then a long period of stability until speed of processing begins declining from middle age to senility (Salthouse, 2000).[19] In fact, cognitive slowing is considered a good index of broader changes in the functioning of the brain and intelligence. Demetriou and colleagues, using various methods of measuring speed of processing, showed that it is closely associated with changes in working memory and thought (Demetriou, Mouyi, & Spanoudis, 2009). These relations are extensively discussed in the neo-Piagetian theories of cognitive development.[20]

During senescence, RT deteriorates (as does fluid intelligence), and this deterioration is systematically associated with changes in many other cognitive processes, such as executive functions, working memory, and inferential processes.[20] In the theory of Andreas Demetriou,[21] one of the neo-Piagetian theories of cognitive development, change in speed of processing with age, as indicated by decreasing reaction time, is one of the pivotal factors of cognitive development.

## MeasurementEdit

Two measuring instruments relying on cognitive chronometry are the Implicit Association Test, or IAT, and the Timed Antagonistic Response Alethiometer, or TARA.

## Mental chronometry and cognitive ability Edit

Researchers have reported medium-sized correlations between reaction time and measures of intelligence: There is thus a tendency for individuals with higher IQ to be faster on reaction time tests.

Research into this link between mental speed and general intelligence (perhaps first proposed by Charles Spearman) was re-popularised by Arthur Jensen, and the "Choice reaction Apparatus" associated with his name became a common standard tool in reaction time-IQ research.

The strength of the RT-IQ association is a subject of research. Several studies have reported association between simple reaction time and intelligence of around (r=−.31), with a tendency for larger associations between choice reaction time and intelligence (r=−.49).[22] Much of the theoretical interest in reaction time was driven by Hick's Law, relating the slope of reaction time increases to the complexity of decision required (measured in units of uncertainty popularised by Claude Shannon as the basis of information theory). This promised to link intelligence directly to the resolution of information even in very basic information tasks. There is some support for a link between the slope of the reaction time curve and intelligence, as long as reaction time is tightly controlled.[23]

Standard deviations of reaction times have been found to be more strongly correlated with measures of general intelligence (g) than mean reaction times. The reaction times of low-g individuals are more spread-out than those of high-g individuals.[24]

The cause of the relationship is unclear. It may reflect more efficient information processing, better attentional control, or the integrity of neuronal processes.

## Application of mental chronometry in biological psychology/cognitive neuroscienceEdit

With the advent of functional neuroimaging techniques, notably PET and fMRI, psychologists started to modify their mental chronometry paradigms for functional imaging (Posner, 2005). Although psycho(physio)logists have been using electroencephalographic measurements for decades before the conception of PET and fMRI, the images obtained with PET have attracted great interest from other branches of neuroscience, increasingly popularizing mental chronometry among a more elaborate breed of scientists 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.[25]

In the 1950s, 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.

In the 1970s and early 1980s, development of signal processing tool for EEG translated into a revival of research using this technique to assess the timing and the speed of mental processes. For example, high-profile research showed how reaction time on a given trial correlated with the latency of the P300 wave[26] or how the timecourse of the EEG reflected the sequence of cognitive processes involved in perceptual processing.[27]

Then, with the invention 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.[28] 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.

## ReferencesEdit

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