AskDefine | Define biometrics

Dictionary Definition

biometrics n : a branch of biology that studies biological phenomena and observations by means of statistical analysis [syn: biometry]

User Contributed Dictionary



  1. The measurement of biological data
  2. The measurement and recording of the physical characteristics of an individual for use in subsequent personal identification.

Extensive Definition

Biometrics (ancient Greek: bios ="life", metron ="measure") refers to two very different fields of study and application. The first, which is the older and is used in biological studies, including forestry, is the collection, synthesis, analysis and management of quantitative data on biological communities such as forests. Biometrics in reference to biological sciences has been studied and applied for several generations and is somewhat simply viewed as "biological statistics."
More recently and incongruently, the term's meaning has been broadened to include the study of methods for uniquely recognizing humans based upon one or more intrinsic physical or behavioral traits.
For the use of biometrics in biology, see Biostatistics.
Some researchers have coined the term behaviometrics for behavioral biometrics such as typing rhythm or mouse gestures where the analysis can be done continuously without interrupting or interfering with user activities.


Biometrics are used to identify the input sample when compared to a template, used in cases to identify specific people by certain characteristics.
  • possession-based: using one specific "token" such as a security tag or a card
  • knowledge-based: the use of a code or password.
Standard validation systems often use multiple inputs of samples for sufficient validation, such as particular characteristics of the sample. This intends to enhance security as multiple different samples are required such as security tags and codes and sample dimensions.

Common human biometric characteristics

Biometric characteristics can be divided in two main classes, as represented in figure on the right:
Recently, a new trend has been developed that merges human perception to computer database in a brain-machine interface. This approach has been referred to as cognitive biometrics. Cognitive biometrics is based on specific responses of the brain to stimuli which could be used to trigger a computer database search. Currently, cognitive biometrics systems are being developed to use brain response to odor stimuli , facial perception and mental performance for search at ports and high security areas. These systems are based on use of functional transcranial Doppler (fTCD) and functional transcranial Doppler spectroscopy (fTCDS) to obtain brain responses, which are used to match a target odor, a target face or target performance profile stored in a computer database. Thus, the precision of human perception provides the data to match that stored in the computer with improve sensitivity of the system.
  • behavioral are related to the behavior of a person. The first characteristic to be used, still widely used today, is the signature. More modern approaches are the study of keystroke dynamics and of voice.
Strictly speaking, voice is also a physiological trait because every person has a different pitch, but voice recognition is mainly based on the study of the way a person speaks, commonly classified as behavioral.
Other biometric strategies are being developed such as those based on gait (way of walking), retina, hand veins, ear canal, facial thermogram, DNA, odor and scent and palm prints.
  • Odor and Scent Cognitive Biometric Systems
In forensics, odor evaluation can make important contributions in both prosecution and defense of criminal cases. The use of blood hounds and other scent following dogs to identify individual people or their scent trails in the environment on the basis of a previous offered reference scent article such as handkerchief, hat, and other items of clothing has been described Canine scent identification evidence is usually accepted in court to suggest the unique identification of an accused individual in the same way that finger prints are used The latter is premised on the alleged factuality of the "individual odor theory," which hold that each person has a unique scent that can be identified by the dog and related back to a specific individual. High courts have accepted the performance of canine scent identification, even when it is claimed that they are detecting the scent of a specific individual at the scene of a crime nearly 2 years after the crime was committed as discussed in the case State v. Eugene Wiley Case No. 8001659, 18th Judicial Circuit, Brevard County Fla. (1982). However, error have been known to occur, and juries have found individuals guilty almost solely on the basis of dog evidence subsequently shown to be unreliable, if not fraudulent as in the case State v. Kevin Roscoe, CR-127656, 11-20-90, Maricopa County, Arizona Superior Court, Judge Paulson. It is therefore imperative that further research studies of the abilities of such scenting dogs be undertaken. Especially, the ability to scent match odors from individuals to handled objects, under controlled laboratory conditions ; However, in some studies dogs have proven capable of performing such scent matching tasks at levels greater than chance, their error rates are seldom more than 10 to 20% Errors may also be introduced by the interpretation of the behavioral response of the dog. What is probably lacking is an objective physiologic correlate of scent matching odors in canine detectives. The latter has the subject matter current research. There is thus ample evidence that in primates olfactory memory has several unique characteristics, the most striking being its resistance to decay over long intervals, suggesting a specialized memory system. However, investigations into the neural substrates of human olfactory memory have been limited. Previous positron emission tomography (PET) studies have shown significant regional cerebral blood flow (rCBF) increases during olfactory stimulation: unilateral in the right orbitofrontal cortex (OFC), and bilaterally in the inferior frontal and temporal lobes (piriform cortex) . A new approach that uses noninvasive transcranial Doppler ultrasound to measure mean blood flow velocities in human and canine subjects during odor presentation is currently being evaluated. The target odor such as bomb making materials (e.g. TNT) or noxious chemicals elicit are first committed to memory in human or canine detectors. A area wide search such as at a seaport or at an airport could produce a matching odor, that triggers pattern recognition by computer. The latter is a brain-machine interface for odor recognition such as that described in United States Patent No. 6,663,571.
  • Facial Cognitive Biometric Systems
The growing threat of terrorism and the aftermath of the Sep. 11, 2001 terrorist attack on the twin Towers of the World Trade Center in New York, has made recognition of the faces of terrorist suspects entering the airports, seaports and border crossings crucial to National Security. However, conventional biometric methods introduced to improve security are static, mainly based on cross matching the face of the traveler with that in the international passport and fingerprints. Although a welcome improvement to the prior situation of total absence of biometric information, its importance in terror crime prevention may be limited. However, it may serve to provide a database of biometric information including faces and fingerprints. At present, the data is static and would not, for example, identify suspects with cosmetic or plastic surgery modification of their faces to escape identification. However, it is possible to train persons that could be referred to as `face-minders`, to memorized faces of suspects on terrorist watch-list, by way of example. The immigration officer trained as a `face-minder` is here referred to as `immigration officer and face-minder`. Trainees could acquire skills of cross-matching key features of faces of persons seen at the ports as compared to that in the immigration or forensic facial database. However to be effective, subjective judgment must be replaced with objective physiologic correlates of good matches. This will require objective online detection of physiologic variables, suggestive of facial memory involvement and cross matching the online variables to expected variables, for the particular face involved. Online brain imaging adapted for use for such applications include electrophysiological techniques and transcranial Doppler ultrasound. One such brain-machine interface method based on functional transcranial Doppler spectroscopy (fTCDS), detects the presence of an equivalent to cortical long-term potentiation (CLTP), in the left middle cerebral artery in male face minders and triggers a search for a matching face, to be reviewed by other observers as described in United States Patent Application No. 20040158155.
  • Cognitive Performance Biometric Systems
Task performance using general intelligence must elicit responses in neural anatomic structures for processing of the information. In task requiring general intelligence there is the necessity of keeping several conceptual formulations in mind such as during Raven's Progressive Matrices (RPM), and is itself a working memory function involving prefrontal cortex . Basso and others demonstrated that post-rolandic structures may be more critical for this general task as shown in patients with brain lesions . Evidence obtained in normal subjects using positron emission tomography studies have shown that high g tasks do not show diffuse recruitment of multiple brain regions, instead they are associated with selective recruitment of lateral prefrontal cortex in one or both hemispheres . It has been shown that working memory is typically associated with activations in the prefrontal cortex (PFC), anterior cingulate, parietal and occipital regions. These brain areas received blood supply from the middle cerebral arteries. Two fundamental working-memory processes have been identified: the passive maintenance of information in short-term memory and the active manipulation of this information . In young subjects, studies using RPM tasks showed areas of regional CBF activation that comprised inferolateral temporal cortex including the fusiform gyrus bilaterally, and the middle temporal gyrus on the left, portions of the left medial temporal cortex including the parahippocampal gyrus, the left inferior parietal lobule, and the cerebellum. The identified anatomic structures (except for the cerebellum) derive major blood supply from the middle cerebral artery. In a study, using functional transcranial Doppler (fTCD), Njemanze demonstrated that for successful resolution of RPM tasks, females used a left hemisphere strategy while males used the right hemisphere. The latter implies that general intelligence is associated with neural systems within one hemisphere that are accessible to a variety of cognitive processes. It was demonstrated that bi-hemispheric activation was associated with Wrong ANSWER, which may suggest that, increasing level of task difficulty is associated with diverse pattern of neural activation due to broad sampling of all major cognitive functions . Njemanze postulated that, successful RPM problem-solving employs a discrete knowledge strategy (DKS), that selects neural pathways represented in one hemisphere. While unsuccessful outcome implicates a non-discrete knowledge strategy (nDKS). RPM paradigm could be viewed as a working memory task. This suggests that the DKS model may have a correlate in mnemonic operations. In other words, DKS model may have a discrete knowledge base (DKB) of essential components needed for task resolution, while for nDKS, DKB is absent, and hence a "global" or bi-hemispheric search occurs. Based on these findings, a brain-machine interface system was designed as described in United State Patent No. 6,390,979. A pattern of blood flow velocity changes is obtained in response to a set intelligence task, which is used to form a 'mental signature' that could be repeatedly recognized, in an automated man-machine interface system. The system is designed to go beyond passive recognition, but rather to set a desired level of 'mental performance', before access is gained into the system. The device could be used as a 'lie detector' based on the fact that, it could distinguish Wrong ANSWER which elicits bi-hemispheric activation, from Correct ANSWER that activates unilateral response.

Comparison of various biometric technologies

It is possible to understand if a human characteristic can be used for biometrics in terms of the following parameters:
  • Universality each person should have the characteristic
  • Uniqueness is how well the biometric separates individually from another.
  • Permanence measures how well a biometric resists aging.
  • Collectability ease of acquisition for measurement.
  • Performance accuracy, speed, and robustness of technology used.
  • Acceptability degree of approval of a technology.
  • Circumvention ease of use of a substitute.
The following table shows a comparison of existing biometric systems in terms of those parameters:
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