Information: ITS nature, measurement, and measurement units
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INFORMATION: ITS NATURE, MEASUREMENT, AND MEASUREMENT UNITS By James R. Simms Simms Industries, Inc.. Columbia, Maryland
The nature of information is identified, and measures and measurement units for information are developed. There are five fundamental characteristics of information, which together comprise its nature: (1) it is an abstract concept, (2) it is weightless, (3) it does not occupy space, (4) it is observable only by the work it causes, and (6) it is transient and perishable.
Information is concisely defined as the ability to cause work. Because work can be measured, information can be measured by the work it causes. Neural information, in the form of electrochemical impulses, causes muscle t issue contract ion which resul ts i n mechanical work. Biochemical information, in the form of enzymes, causes the biological work necessary to rear range biochemical reactants (biochemical reactions). Genetic information, in the form of genes and codons, causes the work necessary to synthesize protoplasm.
Neural, biochemical, and genetic information can be measures by the work thry cause. These measures are equivalent to the extant measures of length, mass, time, temperature , charge, and energy. Units of measure are established for the three forms of information. These units are equivalent to the extant centimeter, gram, second, degree Centigrade, abcoulomb, erg, and calorie measurement units. An individuals behavior is observable by way of mechanical work in the form of muscle contractions, biochemical work in the form of biochemical reactions (metabolism), and work done in the synthesis of protoplasm. Measures of information and the information measurement units provide the basis for developing quantitative living systems and behavioral sciences that can join the community of quantitative hard sciences.
KEY WORDS: information, information parameters, information measures, information units, living systems, nature of information, behavioral science, living systems science TYPE OF ARTICLE: fundamental principles, measures and measurement units DIMENSIONS AND UNITS: cgs, information, information units
ameter of living systems. It is a self- I evident t r u t h t h a t we humans require information and must process information for survival. We inform our skeletal muscles to contract in specific ways to perform the work necessary to obtain and ingest food. Our sensors detect changes in the environment and generate information that causes muscle contraction, for example the knee je rk reaction. Our h e a r t generates
NFORMATION IS A FUNDAMENTAL par- information that causes the contraction of heart muscle. In addition to these self- evident t ru ths , t he re is a robust literature verifying that information is a fundamental parameter of l iving systems. Perhaps the most striking scientific evidence that information is a fundamental parameter of l iving systems was the discovery of the dou- ble stranded helical structure of DNA by Watson and Crick (1953) and the large body of genetic l i terature t h a t followed. More specifically, Miller (1978)
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identified information and information processing as an essential characteristic of living systems. Miller and Miller (1995, 171) reiterated the principle tha t information and information processing are essential characteristics of living systems.
Although information is a funda- mental characteristic of living systems, i ts na ture i s not well understood. Certainly its na ture is not under- stood as well as the fundamental characteristics of physical systems, such as size, mass, changes of parameters with time, temperature, charge, and energy.
The existing concepts of information are neither precise nor invariant. For example, common usage of the word information includes synonyms such as data, fact, news, and intelligence, as well as knowledge obtained from investigation, study, o r instruction. Communication systems usage of the word information covers a wide spectrum, including: (a) any exchange between individuals in which a message is generated by one individual that can be received by a sensor of the target individual(s); (b) a message transmission medium such as telephone, telegraph, radio, television, or print; and (c) Shannons (1949) classical information theory.
Legal usage of the word information is the formal accusation of a crime. Living systems theory usage includes the concept tha t information is a fundamental property of all living systems (Miller, 1978). Biological usage includes genetic, biochemical, and neural information. Computer science usage includes information processing.
The foregoing, though not an all- inclusive list of the various concepts and usages of the word information, illustrates the lack of clarity and precision in our understanding of the nature of infor- mation. Also, there currently is neither an accepted measure for information nor accepted information units.
Emergence of the extant community
of quantitative sciences has occurred only after the discovery of the nature of a fundamental parameter and the invention of a measure and measurement units for this parameter. Emergence of a quantitative living systems science that can join the extant community of quantitative sciences depends on the discovery of the nature of information and on the invention of measures and measurement units for information.
GENERAL CHARACTERISTICS OF INFORMATION
The general characteristics of things are usually identified and defined in terms of observations made by our senses. Matter is a good example: (1) its weight is determined by our kinesthetic senses; (2) its size is determined by our visual senses; (3) outgassing of mat te r is determined by our sense of smell; (4) its chemical composition is determined, to some degree, by our sense of taste; and (5) temperature, roughness, and surface geometry are determined by our tactile senses.
Our senses fail us when we try to determine the general characteristics of information. We cannot determine the relative weight of our o w n or another individuals genetic, biochemical, or neural information by our kinesthetic sense; we can only conclude that i t is weightless. We cannot determine the sue and shape of genetic, biochemical, and neural information of animals because we can neither see them with our eyes nor feel them with our tactile sensors. We can only conclude that information does not occupy space. Even with the best instruments to enhance our sensors, such as the electron microscope, we can neither see nor feel information, Our senses of tas te and smell a r e of no assistance because information does not smell nor cause a taste sensation.
The lack of positive sensory identification of t h e general char- acter is t ics of information actual ly
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defines the general characteristics of information in a negative way, that is, what information does not have or what i t is not. Information is weightless and does not occupy space. These two impor t an t character is t ics a r e also fundamental characteristics of energy. These fundamental characteristics lead t o t h e impor tan t conclusion t h a t information, just like energy, cannot be directly observed.
Our inabi l i ty t o observe and characterize information by our sensors leads to another important conclusion. We cannot directly measure information by the fundamental measures of length, time, mass, temperature, and charge because these measures are based on our senses. The measure of length is based on our 3-D vision, which results from having two eyes that are physically separated. The measure of time is based on our visual observation tha t things age. The measure of mass is based on the self-evident t ru th t h a t different mater ia l s act ivate our kinesthet ic senses differently as a function of their weight. The measure of temperature is based on the self-evident truth that a substance can feel warm or cold.
The inabili ty t o directly measure information i s another impor tan t characteristic tha t information shares with energy. This lack of abil i ty t o directly observe and measure energy results in energy being characterized as an abstract concept. Since information, like energy, is not directly observable and measurable, i t i s appropriate t o describe information also as an abstract concept.
Although direct observation and measurement are not possible for these two abstract concepts, energy has been characterized indirectly in terms of work, which is observable and can be measured or calculated. In science and engineering, energy is defined as the ability to do work. The work associated with various forms of energy has been identified and measurement un i t s
established-for example, mechanical energy, the erg; heat energy, the calorie; and electrical energy, the watt-second.
I t was determined earlier (Simms, 1983) that the behavior of systems could be observed only through the energies (work) tha t were associated with tha t behavior. This determination was based on Rosens (1978) proof that na tura l systems can be observed, and measured only in terms of their energies. Because the observed energy of a behavior can be measured or calculated, the behaviors of systems can be quantified.
The above considerations resulted in identification of t he following general characteristics of information. Information:
Is an essential property of living
Is an abstract concept. I s weightless and does not occupy
Cannot be directly observed. Cannot be directly measured. Has many of the characteristics of
systems and their behaviors.
EMERGENCE OF THE QUANTITATIVE SCIENCES
An analysis was made of the evolution of the extant quantitative sciences t o determine processes that could be used as models for the development of a quantitative living systems science. This analysis revealed t h a t each of the quantitative physical sciences is based on (1) an understanding of the phenomena concerning the behaviors of the subjects of the science, (2) the discovery andor use of one or more fundamental measures, and (3) the quantitative sciences which were extant before the evolution of the new quantitative science.
Because the analysis revealed tha t bdamenta l measures are essential to the development of quantitative sciences, the characteristics of fundamental measures must be understoo& These char&ristics are:
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*The concept associated with the measure is self-evident, i.e., axiomatic. For example, the concept of length is self-evident because the presence of two eyes allow depth perception. Also, i t t akes more effort t o walk t o a more distant place than to one that is near.
The measurement unit is defined in terms of an invariant, or approximately invariant, physical phenomenon.
The measurement unit is arbitrary, that is, it must be accepted by a consensus of the users of the unit.
The fundamental unit cannot be reduced to another more fundamental measure. The mathematical concept of counting is understood so that one unit (a sin- gle count) can be determined.
Figure 1 captures the essence of the evolution of t h e nonliving systems sciences and provides a convenient means for summarizing the essential elements of this evolution. The evolution of fundamental measures is shown from
left t o right across the lower portion of Figure 1. The boxes show fundamental laws and quantitative sciences, and the lines between the boxes show the fundamental measure and the extant quantitative science necessary for the evolution of the next quantitative science.
Length, time, and mass are shown in Figure 1 as fundamental measures. Each has the characteristics of fundamental measures listed above.
Many different units of length evolved over the long history of humankind (Petrie, 1951). For example, one such unit is the cubit which was used in Egypt from the time of the predynastic period onward. In Europe, prior to the 19th century, each country had its own system or systems of weights and measures. In China, the situation was very complicated since units differed in value from place to place, and in the same locality people connected with different trades had conflicting units. Various uni ts of t ime and mass, like length, have been traced t o ancient
FIGURE 1 Emergence of the quantitative sciences.
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times. For example, the oldest standard of mass known is the beqa, found in early Amratian graves in Egypt (7,000- 8,000 B.C.). Currently, the English system, established by the beginning of the 19th century, and the metric system, established in 1791, are widely accepted systems of fundamental units
Geometry is shown in Figure 1 as the first quantitative science. The generally accepted account of the origin and early development of geometry is t ha t the ancient Egyptians were obliged to invent i t in order to restore the landmarks which were destroyed by the periodic inundations of the Nile (Newman, 1956, lo). The science of geometry was invented considerably earlier than 1000 years B.C. The very name geometry is derived from two Greek words meaning measurement of the earth. These measurements are based on the fundamental measure of length. Because geometry is, in essence, the relationship among various lengths, no other fundamental measure is necessary for this quantitative science.
Although not shown in Figure 1, Copernicus provided an understanding of the basic phenomena of astronomy when he conceived the heliocentric theory-reviving Pythagorean beliefs- and worked i t out in his famous book De Revolutionibus Orbium Coelestrium. Johann Kepler used the fundamental measures of distance and time and the quantitative science of geometry to bring quantitative precision t o Copernicus theories. Kepler used these measures to develop quantitative relationships for the motion of planets. These relation- ships, known as Keplers laws, provide t h e fundamenta l principles for t he quantitative science of astronomy.
I t is noted that the unit of time meets all the requirements for a fundamental unit. I t is self-evident that time passes, t h e un i t of t ime is based on the invar ian t physical phenomenon of planetary motion, and the definition of a t ime uni t i s arbitrary and i s agreed upon by the community of users of time
measures. As shown in Figure 1, the hndamental measures of length and time, along with the measurement science of geometry, are all prerequisites for the development of the quantitative science of astronomy.
Keplers work resulted in three hndamental laws. The first law states that the planets move in ellipses with the sun in one focus. The second law states that the line joining sun and planet (the radius vector) sweeps out equal areas in equal times. The third law (Newman, 1956, 218) was published in 1618, nine years after the other two. I t connected the times and distances of the planets: The square of the time of revolution of each planet is proportional t o the cube of its mean distance from the sun.
The next quantitative science to evolve was Newtons mechanics, as shown in Figure 1. Newton investigated those phenomena associated with mass, particularly the attraction of masses to one another. These investigations required a fundamental measurement unit for mass. The famous Newtons laws were the result of investigations into the relationships among length, time, and mass. Newtons discovery of his laws depended on the preexistence of fundamental measurement units of length, time, and mass, and on the existence of geometry and Keplers work.
Newtons Principiu, consisting of three books, records the basis for his mechanics. The first book treats his laws of motion and lays down his mechanical foundations, clearly formulated for the first time. The second book is devoted t o motion in a resisting medium and is the first treatment of the motion of real fluids. The third book of the Principiu, published in 1687, is the crown of the work and changed the face of science. In this book he establishes the movements of the satellites around their planets and of the planets around the sun on the basis of universal gravitation.
The next phase of evolution, as shown in Figure 1, is the quantitative science of hea t . The n a t u r e of h e a t and i t s relationship t o temperature had been
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debated at leas t since the ancient Greeks. I t was not until the invention of the thermometer tha t a fundamental measure of temperature was established and a quantitative hea t science could evolve. The evolution of the fundamental measure of temperature follows.
Since knowledge of the properties of matter can be gained only through sense perception, every fundamental quantity must be ultimately defined in terms of received sensations. The temperature of a substance may thus be qualitatively defined as the property of the substance that determines the sensation of warmth or coldness received from contact with it (a self-evident truth). Observation of the substance reveals t ha t if a change in temperature is taking place, there is a simultaneous change in other physical properties of t he substance. These changes include: change in volume, change in pressure (at constant volume), change in electrical resistance, change in radiat ion from t h e surface, and change in state. The changes in these various physical properties are usually susceptible to accurate measurement.
The earliest devices used to measure temperature were known a s thermo- scopes. The invention of the thermoscope has been variously ascribed (Cork, 1942) to Galileo Galilei in 1593, C. Drebbel in 1609, Paolo Sarpi in 1610, Sancttario Santario in 1611, and G. della Porta in 1610. The measure of temperature and the self-evident warmth and coldness characteristics described above prove t h a t tempera ture i s a fundamenta l measure. T h a t is , i t i s self-evident because (a) the warmth or coolness of substances is felt, (b) the measure is related to measurable physical phenom- ena, (c) the unit of measure is arbitrary and is determined by the users of the measure, and (d) the measure cannot be reduced to a more fundamental measure. Emergence of the quant i ta t ive hea t sciences occurred after the invention of the thermometer and after J. P. Joule announced in 1847 t h e law of t h e
conservation of energy as applied t o thermal processes.
The quantitative science of electricity is shown in Figure 1 as the next step in t h e evolution of t h e quant i ta t ive sciences. This science could not evolve until the fundamental measure of charge was discoveredlinvented. A fundamental measure of charge was established by Coulomb in his electrical papers, which were published in the Memoirs de I Academie royale des science between 1785 and 1789. T h e charge on t h e electron was established by Robert A. Millikan in 1913 (Millikan, 1935). Both these measures a r e based on t h e mechanical sciences. The Coulomb is based on the force of repulsion between like charges. The charge on the electron is based on attraction of unlike charges and on the effects of gravity. Both force and gravity effects are concepts of the mechanical sciences. Other quantitative electrical science measures such as the volt, ampere, and watt are derived from the fundamental measure of charge.
I n addition to t he fundamenta l measures based on the above-described self-evident t ruths , Figure 1 shows a measure of energy. Unlike the measures of length, time, mass, temperature, and charge, which a re based on concrete matter, the measure of energy is based on an abstract concept. That is, energy is weightless and does not occupy space. The fundamental definition of energy is: the abil i ty t o do work. Energy i s measured by the amount of work performed. The work performed can be mechanical, thermal (heat), or electrical. Therefore, the types of energy include mechanical, heat, and electrical. The work associated with the various forms o f energy h a s been identified a n d measurement uni t s established, for example: mechanical energy, the erg; h e a t energy, t he calorie; electrical energy, the watt-second. Work i s a dynamic phenomenon because i t i s associated with time, such as the watt- second, and thereby can be considered as
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a behavior. Because of these differences in characteristics between energy and the fundamental measures of length, time, mass, temperature, and charge, energy is shown differently in Figure 1. Energy is identified in this figure as an abstract concept.
Figure 1 shows the evolution of another quantitative science, namely quantitative living systems science, and the evolution of another fundamental measure, namely behavioral information. The fundamental measure of behavioral information has been identified and a method developed for measuring neural behavioral infor- mation (Simms, 199 1).
The most important result of the analysis of the evolution of the quantitative sciences i s t he reaffirmation of the following:
Development of the quantitative sciences is truly evolutionary with each new quantitative science depending on the sciences that preceded it.
*Measurement of the phenomena asso- ciated with the subjects of the science is essential t o the development of a quantitative science. Each of the quantitative sciences evolved only after the establishment of the fundamental measure of a basic parameter associated with the science. . Fundamental measures and units of measure relating t o the science are prerequisites to the development of a quantitative science.
These facts provide the basis of a model for the development of a a quantitative living systems science based on the measurement of information.
NATURE AND MJL4SuRE OF NEURAL INFORMATION
The general characteristics of information and the models for emergence of the extant quantitative sciences provide the basis for further specification of the characteristics of information. Following
the emergence model, the most obvious and readily observable phenomena are treated first. The most obvious living systems behavioral phenomena are those resulting from the muscle contractions of animals, which, in turn, are caused by electrochemical impulses in motor neurons. The nature and measure of neural information have been developed (Simms, 1991).
The central concepts of this earlier work are: (1) the most obvious behaviors of animals a re those associated with muscle contraction, (2) muscles a re composed of motor units, (3) motor units consist of a motoneuron and the muscle fibers associated with this motoneuron, (4) a motor unit has a capacity to direct energy, that is, it has a capacity to convert chemical energy in the form of ATP (adenosine triphosphate) into work and heat, (5) a motor unit converts chemical energy to work and heat only when there i s an electrochemical impulse in i t s motoneuron, (6) this impulse invariably causes the muscle fibers to contract and thereby causes the motor units behavior, (7) the electrochemical impulse carries a message for the motor unit to contract, that is, the impulse carries information, (8) the work and heat energy in the motor units behavior (i.e., its contraction) can be measured or calculated, (9) the chemical energy utilized in a contraction behavior can be measured or calculated, (10) an impulse in a motoneuron can be con- sidered as a quantum of information, and (11) the amount of energy that a quantum of information causes to be utilized by a specific motor unit can be measured or calculated.
Any measurement requires a unit of measure; a measure of information is not exempt. Inasmuch as energy and information a re similar and related abstract concepts, development of the heat energy unit, the calorie, was used as a model for the development of a n information measurement unit . The calorie unit is based on the phenomenon that a heat input into a substance will
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increase the temperature of the substance. The amount of heat increase depends on the characteristics of the substance, that is, its specific heat capacity. The calorie is based on the selection of a specified substance (water) and the increase in the temperature of a specific amount of water by a one-degree increment under specified conditions. The amount of heat that causes this temperature increase is defined as a calorie.
Using this hea t energy model, the information uni t is based on the phenomenon that an information input into a specific motor unit causes i t to convert a specific amount of chemical energy into work and heat. A sartorius motor unit of the frog Rana pipiens was selected as the behaving element. The unit of information is defined as the amount of energy converted by this reference behaving element when caused to do so by an impulse (single quantum of infor- mation). For these conditions, a quantum of neural information will cause a specific amount of energy to be utilized in the contractile behavior. The information unit derived using this model is: one unit (quantum) of behavioral information causes the production of 18.5 microcalories of energy by a Rana pipiens sartorius motor unit at a temperature of 0C and loaded to 0.45 of its peak tension load.
A quantum of neural information will cause other motor units t o convert an amount of energy that is different from that converted by the reference Rana pipiens motor unit , the difference depending on the specific characteristics of the other motor units. The ratio of a motor units capacity t o direct energy t o the reference Rana pipiens sartorius motor units capacity t o direct energy i s the motor units specific capacity t o direct energy. The specific capacity to direct energy of motor units is comparable t o the specific hea t capacity of sub- stances.
Subsequent ly , other muscle con- traction behaviors that are caused by neural information were investigated
(Simms, 1995). These include the obvious behaviors of motion and locomotion, breathing, heartbeat, and food ingestion and food byproduct ejection. The basic characteristics of these behaviors are the same as for the sartorius motor unit of Rana pipiens; the muscles which cause each of these behaviors consist of motor units, each with its own specific capacity to convert chemical energy into the work and heat energies, i.e., behavior. Of particular interest is the heart muscle, which acts as a single motor unit with a quantum of neural information from the hearts pacemaker causing the contraction of the complete heart muscle. One quantum of neural information to the heart was calculated to cause the conversion of one calorie of chemical energy t o the work and heat energy in a single heartbeat (Simms, 1995). The hear t muscle can be used a s the elemental behaving system to determine a different unit of neural information. This unit is: one quantum of neural information causes the production of one calorie of behavioral energy (i.e., work).
NATURE AND MJL4STJR.E OF BIOCHEMICAL INFORMATION
Biochemical information is as different from neural information as mechanical energy is from chemical energy or heat energy. The observable behaviors asso- ciated with biochemical information are biochemical reactions. Metabolism, the sum of all biochemical reactions taking place in an organism, is a key characteristic of all living systems. Virtually all organisms have a group of biochemical reactions which, taken together, is called glycolysis. The biochemical reactions of glycolysis are the initial reactions in the process that converts the chemical energy in glucose into chemical energy in the form of ATP (adenosine triphosphate). The ATP molecule provides short-term storage o f energy and provides the energy t o perform biological work. Biochemical reactions occur when (a) there are structures in a living systems cells to
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allow the reaction, (b) substrates are present, and (c) there is a specific enzyme that causes each of these biochemical reactions. The molecules that are acted upon catalytically are called the enzymes substrates. It is an established fact that biochemical reactions do not occur without being caused to do so by enzymes.
Biochemical reaction can be described in a general way as the rearranging of the chemical elements. The reacting molecules in a biochemical reaction form other molecules and either require chemical energy o r release chemical energy. From a behavioral point of view, the observed behavior is the rearrangement of chemical elements and a conversion of energy from one form to another. Also from a behavioral point of view, an enzyme causes a biochemical reaction and therefore h a s the char- acteristics of information in that i t causes a behavior. A particular enzyme molecule carries a single message for a specific behavior of rearranging the elements of molecules. That is , one quantum of chemical information transported by an enzyme causes a single chemical reaction.
The chemical reactions just described take place inside a living systems cell and are caused by information generated inside the cell. In contrast, hormonal information-also biochemical infor- mation- is generated in cells within special organs (the endocrine glands) and is transmitted, via a circulatory system, to targeted cells where they cause bio- chemical reactions. From a biochemical information point of view, information is generated in the endocrine glands in the form of a specific hormone molecule (a quantum of biochemical information). This quantum of information is transmitted to a targeted cell which accepts this information and causes a specific biochemical reaction. The actual processes for the generation, transmission, and utilization of biochemical information are complex (Purves, Orians and Heller, 1992, 782-785) but can be highlighted as follows.: There are two
general mechanisms by which chemical messages a re read by the cells t h a t receive them: one for water-soluble hormones such as t h e peptide and protein hormones, and one for the lipid- soluble hormones ( the s teroids and thyroxine). The major difference between these two mechanisms is that the water- soluble hormones cannot penetrate a target cells plasma membrane and must act through a second message, whereas the lipid-soluble hormones can readily penetrate the target cells membrane and cause biochemical reactions inside the cell.
T h e biochemical information described above i s associated with behaviors internal to a n individual. Biochemical information also is trans- mitted externally from one individual t o ano the r . Animals receive info- mation about chemical stimuli through chemosensors tha t respond to specific molecules in the environment. Chemo- sensors are responsible for smell, taste, and the monitoring of aspects of the internal environment such as the level of carbon dioxide in the bloodstream. Chemosensitivity is universal among animals. For example, arthropods use chemical signals, called pheromones, to a t t r a c t ma tes . To i l l u s t r a t e t h i s information behavior phenomenon, a female si lkworm moth r e l eases a pheromone called bombykol which is received by a male s i lkworm moth by sensors for this molecule on h i s an tennae . Each f ea the ry a n t e n n a ca r r i e s about 10,000 bombykol- sensitive hairs, and each ha i r has a dendrite of a sensor cell at its core. A single molecule of bombykol i s sufficient t o activate a dendrite and gene ra t e act ion po ten t i a l s in t h e an tenna1 nerve t h a t t r a n s m i t s t h e signal t o the central nervous system. When approximately 200 h a i r s per second a r e activated, the male fl ies upwind in search of the female (Purves, Orians and Heller, 1992, 846-847). The structure of this behaving system is the
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females g l ands t h a t gene ra t e t h e chemical information, the transmission system which is the atmosphere, the conversion from chemical information t o neural information by t h e males antennae, and the further transmission of neura l information t o t h e fl ight muscles which convert chemical energy to the work involved in flight and to heat. In this case, the information was generated as chemicals, transmitted from one individual through the atmosphere as chemical information, then converted into neural information by the receiving individuals sensors. Information is then transmitted in the receiving individuals central nervous system to motoneurons, and finally transmitted to the muscles of flight which produce the observable behavior.
The above considerations verify that the basic characteristics of biochemical and neural information are the same. These considerations also verify that the behaviors caused by biochemical information can be measured in terms of energy utilized in the behavior.
A measurement unit for biochemical information was developed using the model for developing the unit for heat energy and following the techniques used for developing the measurement unit for neural information. Selection of a reference biochemical reaction for the development of a biochemical information uni t was based on the following criteria: (1) the reaction occurs in virtually all organisms, (2) the biological work required by the reaction is provided by a single molecule of ATP, (3) the enzyme that causes the reaction is known, (4) the amount of chemical energy required by the reaction is known, and ( 5 ) sufficient data is available to describe the reaction and its behavior. The first reaction in the glycolysis process met these criteria and was selected as the reference biochemical behaving element. A number of other reactions could have been selected because many different enzymes can cause the release of free energy from
ATP. However, the glycolysis reactions are perhaps better known.
The f i r s t biochemical reaction of glycolysis is the conversion of glucose to glucose six-phosphate by the transfer of phosphate, from ATP to the six-carbon sugar glucose. The ATP provides the energy used i n t h e reaction (ap- proximately 12 kilocalories of free energy per mole). Conversion from energy per mole to energy per molecule of ATP, by use of Avogadros constant, results in approximately 2 x 10-20 calories of free energy per molecule of ATP. This is the amount of energy caused to be utilized in the biochemical reference reaction by one quantum of biochemical information. The biochemical information measurement unit is approximately: one quantum of biochemical information causes the utilization of 2 x 10-20 calories of energy in the reference behaving system.
This biochemical information unit is approximate because the reference biochemical reaction system and its environment have not been completely specified. This lack of specificity introduces uncertainties in the amount of free energy provided by ATP. The actual amount of energy provided varies as a function of the concentrations of ATP, adenosine diphosphate (ADP), and a phosphate ion. The amount of energy is also a function of temperature and PH. The biochemical information unit can be made precise by specifying the temperature, PH, and concentrations of ATP, ADP, and phos- phate ion that results in exactly 2 x 10-20 calories per quantum of biochemical information.
NATURE AND MEASURE OF GENETIC INFORMATION
In biology the word information was rarely used prior to the mid-1950s and then usual ly in connection with hormones. The word hormone was coined by Bayliss and Starling in 1902- 03 from the Greek word for I arouse to activity. After t ha t time, it became
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rather common t o speak of hormonal information. The work of Watson and Crick (1953) on the na tu re of t he double-stranded DNA molecule resulted i n t h e emergence of t he genetic information concept. Today the genetic information concept is a central dogma of molecular biology.
Genetic information causes the production of specific proteins. This information i s encoded i n DNA (deoxyribonucleic acid), the genetic mater ia l , which consists of two polynucleotide chains forming a double helix. The central dogma of molecular biology i s t h a t DNA codes for RNA (ribonucleic acid) and RNA codes for protein.
Like neura l and biochemical information, genetic information is weightless and does not occupy space. Also l ike neura l and biochemical information, genetic information is generated in one location and then transmitted to another location where it causes a particular behavior. Genetic information generated by DNA causes the synthesis of protoplasm. This DNA information i s transcribed into two types of RNA t h a t travel t o the cytoplasm. One is a messenger RNA, the other is a t ransfer RNA which recognizes the genetic message and simultaneously carries specific amino acids, thus translating the language of DNA into the language of proteins. Genetic information is also like neural and biochemical information in that it cannot be directly measured, but must be observed and measured by way of i ts behavior, the production of proteins.
The production of protein requires an expenditure of chemical energy stored in molecules of ATP. The amount of ATP required for the production of specific proteins can be calculated and represents the energy required for the protein production behavior. The production of protein also requires biochemical reactions tha t are caused by specific enzymes (biochemical
information). The mechanisms for the production of protein are known, and the chemical reactions, energies, biochemical information, and genetic information have been identified (Purves, Orians and Heller, 1992,236-265).
The facts and considerations given above demonst ra te t h a t genetic information has t h e same general characteristics as neural and chemical information.
A measurement unit was developed for genetic information based on the model used for the development of a unit of measure for neura l information. Selection of a reference protein syn- thesis system for the development of a genetic information unit was based on the following criteria: (1) the protein synthesized is simple, consisting of two linked amino acids, (2) the enzymes that causes the biochemical reactions are known, (3) the biological work required for synthesis is known, and (4) sufficient data is available to precisely describe the reference protein synthesis system and its processes. A reference protein synthesis system that produces an end product protein consisting of the amino acids methionine (met) and proline (pro) meets these criteria. The end product is the dipeptide protein met-pro that floats in the cytoplasm.
The reference protein synthes is system consists o f (1) t he DNA molecule; (2) t h e mechanism for converting the genetic information in DNA t o genetic information in RNA; (3) two types of RNA, one a specific type of RNA molecule that is a complementary copy of one strand of the gene, called a messenger RNA o r mRNA, and the other a specific transfer RNA o r tRNA; (4) enzymes (aminoacyl-tRNA synthetases); and (5) ribosome con- sisting of two subunits, a large, or heavy one and a smaller or light one. This system uses one DNA s t r and , "the template strand" in transcribing genetic information in DNA in to RNA information. The genetic information in
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RNA resides in mRNA and in tRNA. The system u s e s biochemical infor- mat ion i n t h e form of enzymes to perform the biochemical reactions of converting from one form of genetic information to another, and of binding methionine a n d proline amino acids to t h e i r respective tRNAs to form charged tRNA molecules. The systems transmission medium transports these charged tRNA molecules to a cells ribosome, where they are operated on to synthesize protein.
T h e u n i t of m e a s u r e for genet ic information was derived from the work this information causes in the synthesis of the reference methionine-proline protein. Protein synthesis is a complex process-a simplified process is used to describe the reference protein synthesis system. The simplified process is to: (1) identify t h e gene t h a t contains t h e genetic information (i.e., codes) for synthesis of t h e methionine-proline protein, 2) identify how th is genetic information is t r a n s m i t t e d to t h e synthesis site ( the ribosome) and the form i t takes in the transmission, (3) identify t h e biochemical react ions necessary to synthesize the reference protein, (4) identify the biochemical energy and the amount of this energy necessary to perform the work t o synthesize the reference protein, a n d (5) relate the genetic information to the total work.
The reference system gene consists of t h r e e codons: one for t h e process initiator methionine, one for proline, a n d one t o t e r m i n a t e the synthes is process. Genetic information is encoded in codons (three-letter words) comprised of the bases; uracil (U), cytosine (C), adenine (A), a n d g u a n i n e (GI. For example, the codon for methionine is AUG a n d for te rmina t ion is UGG. Transmission of the reference gene is initiated by the generation of a mRNA a n d two tRNA molecules. These molecules travel from the nucleus to the cytoplasm of a cell. T h e genet ic information is now in a form t h a t can
cause synthesis of the reference protein, Synthesis begins with biochemical
reactions that charge the two tRNAs: a charged tRNA has been combined with the specific amino acid i t is coded for and its energy level has been increased by ATP. Enzymes cause the charging of tRNA. T h e ATP molecule i n each react ion i s converted to AMP a n d releases approximately 24 kilocalories per mole of free energy. This energy provides the biological work necessary t o charge a tRNA.
Synthesis is completed in a ribosome structure where the genetic information encoded in the mRNA is interpreted by t h e charged tRNA molecules. T h e energy in the charged tRNAs is used to perform the work necessary to combine the two amino acids to synthesize the reference protein.
T h e genet ic information in t h e reference system causes the work in the ribosome necessary to synthesize the dipeptide methionine-proline. This work is derived from the energy added to the tRNAs from the ATP that charges them. Assuming half of the free energy from ATP is used to combine t h e tRNA molecule and the amino acid molecule, the other half (12 kilocalories per mole) is used t o increase t h e energy level of t h e charged tRNA. T h e genet ic information i n t h e gene causes 24 kilocalories p e r mole of work i n synthesizing the reference protein, 12 kilocalories per mole from each of the two charged tRNAs. U n d e r t h e s e conditions, the genetic information for t h e reference sys tem causes 24 kilocalories per mole of work in t h e synthesis of the reference protein.
Because a gene consisting of three codons is the smallest-size gene that can synthesize a dipept ide protein, t h e information in a three codon gene is considered t o be a quantum of genetic information. An approximate u n i t of genetic information is: one quantum of genet ic information causes 24 kilocalories per mole of work to
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INFORMATION: ITS NATURE, MEASUREMENT, AND MEASUREMENT UNITS 101
synthesize the reference protein. This unit converts to: a quantum of genetic information causes 4 x1O-20 calories of work to synthesize one molecule of the reference protein. This approximate genetic information unit can be made precise with specificity of the reference system and accurate measurement of the energies used in protein synthesis.
NATURE AND ~ A S U R F : OF GROUP INFORMATION
In addition to the information associated with the behavior of indi- viduals as given above, information between individuals is essential for survival of their species. Group infor- mation is defined as any information generated by an individual, transmitted via some medium to one or more target individuals, and received by the individual(s) where i t causes, or can cause, behaviors in the receiving indi- vidual(s). This definition recognizes that the nature of information is such that i t can only be observed by the behavior it causes. It also recognizes that information from another individual may be negated by information generated internally by the receiving individual. That is, the information generated by an individual has the potential t o cause a specific behavior in a receiving individual provided it is not negated by that individual.
The nature of group information can be determined by considering a relatively simple elemental group behavioral system. Such a system is the fertilization of an egg by a sperm in sexual reproduction behavior. This group behavior is widespread among living systems and is essent ia l for species survival. The elemental behaving system consists of an egg, sperm and an environment that allows movement and will support chemical information transmission. The behavior of this elemental system is that chemical information i s produced by the egg, transmitted by a fluid environment, and
received by target sperm(s1, which are then caused to swim toward the egg. The observed swimming behavior of sperm is the result of the whiplike stroke pattern of flagella. The protein dynein is responsible for generating the force of flagella. Dynein is a mechanoenzyme (chemical information carrier) that catalyzes the hydrolysis of ATP and uses the released energy to change its orientation, thereby generating mechanical force. The chemical infor- mation transmitted by the egg is received by a sperms chemical sensors and used to determine the direction to the egg.
As animals structures become more complex, so do their behaviors and the information that causes these behaviors. By way o f i l lustration, consider the mating behaviors of deer and dogs. They both depend strongly on chemical communication for mating, but both also use information transmitted by sound waves and by electromagnetic waves. The females of both species generate chemical information when they are in h e a t a n d disperse t h e chemical information carriers into the atmos- phere. These chemicals are received by the males where they cause internal behaviors such as the swelling of glands, and externally observed behaviors such as movement toward the female and a host of other more subt le behaviors associated with mating. Information in the form of sight and sound also is used in the mating behaviors. Although more complex, these behaviors are observable by way of the energy used in the behaviors, and the information associated with these behaviors can be identified. The methods used to measure or calculate this mating information are the same as those described above for individual behaviors.
NATURE AND MEASURE OF HUMAN GROUP INFORMATION
Human group information for primitive peoples probably does not differ markedly from those species
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whose DNA is much like ours. Sagan and Druyan (1992) s ta te t h a t if the sequences of humans and chimpanzees DNA a r e compared nucleotide by nucleotide, they differ by only 1.7%. Because DNA determines structure and organization, and because these two characteristics determine the behaviors of species, it is expected that the nature and measure of their respective group information would differ little.
However, as humans evolved, their technical and social innovations greatly changed the nature of human group information. These innovations include (1) language and i ts ever-increasing robustness, which enables more and more sophisticated behaviors, (2) methods to reduce the perishability of information, such as writing and pictures that allow information t o be passed over great periods of t ime, and (3) methods of transmitting information over greater and greater distances in a relatively short period of time. Language did not change the fundamental nature of information. A behavior is still caused by information, but more precise and varied behaviors can be observed when individuals generate more precise group information due to the increased robustness of their language. However, the relationship between observed behavior and group information is still clear.
The innovations t h a t reduced the perishability of information greatly changed the nature of human group information. After these innovations, an individual could generate infor- mation t h a t may be delayed in transmission for long periods of time, and when received by individuals with a capability t o convert t h i s delayed information t o a form suitable for i ts effectors, could cause a behavior by these individuals. I t may be appropriate t o call t h i s delayed information potential information, as i t has the potential for causing behavior at some significant time after i ts generation. This potent ia l information will
disappear if individuals living in a much la ter time period no longer have the ability to receive it. For example, the potential information written in long lost languages cannot now cause i t s intended behaviors.
The innovations of long-distance transmission of information provide a means for the broadcast of information to many individuals located in faraway places. This broadcast of information is a long-distance version of chemical information broadcast by a n egg t o many sperms, or by a female deer or dog t o many males. The concept i s t he same, it is just the increased distances that are different.
These considerat ions of human innovat ions demonst ra te t h a t t h e nature of information is the same for all animals, except that human innovation h a s provided a means for s tor ing information in the transmission medium and for increasing the distance t h a t information can be transmitted.
The word information has been used in many ways and there are different concepts of t he phenomenon called information. Analysis of these many usages and concepts reveals t h e following basic nature of information: (1) i t i s a n abs t rac t concept, (2) it i s weightless and does not occupy space, (3) i t can be observed only by the work i t causes, (4) i t can be defined as t h a t phenomenon which causes a l iving systems behavior, ( 5 ) i t can be measured or calculated based on the work i t causes, and (6) i t is ephemeral except for the innovations of humans t h a t provide a means for s tor ing information in t h e t ransmiss ions medium and for increasing the distance that information can be transmitted.
The basic n a t u r e of information provides a foundation for the develop- ment of a measure for information that i s equivalent t o t h e fundamenta l
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INFORMATION: ITS NATURE, MEASUREMENT, AND MEASUREMENT UNITS 103
measures of the quantitative sciences. The nature of information that provides a foundation for measuring information includes: (1) information is an abstract concept, is weightless a n d does not occupy space and therefore cannot be measured directly; and (2) information causes a living system to utilize energy, which, in turn, causes a n observable behavior. The concept of measurement is that one q u a n t u m of information causes a living system to use a specific a m o u n t of energy i n affecting a behavior. Because energy can be measured, information can be measured or calculated in te rms of the energy used in a behavior,
U n i t s of m e a s u r e have been developed for neural, biochemical and genetic information.
T h e major conclusions a r e t h a t information is the ability to cause work and that information can be measured by the work it causes.
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