Recent advances in neuroimaging through functional magnetic resonance (fMRI) have offered the hope of uncovering the physical mechanisms behind seemingly metaphysical cognitive processes that shape emotion, sexuality, social interaction, and consciousness—topics that have fascinated and frustrated scientists and philosophers for millennia. Under investigation among these perennial puzzles of human behavior is deception, the understanding of which could profoundly affect law enforcement, anti-terrorism, medicine, and even the day-to-day lives of average individuals. Yet the usage of fMRI to reveal the complex patterns of neural activation underlying even the simplest lie is still in its nascence. Technical and ethical hurdles abound between research into deception in the lab and practical results for the real world. In light of these difficulties, the application of fMRI to define and detect deception currently remains infeasible.
The deliberate negation of truth by a human being, the communication of beliefs that the individual considers untrue, has remained one of the great philosophical, religious, and scientific fascinations of our species. From the writings of the Ptahhotep peoples of five millennia past (Chinweizu 2001, cited in Spence 2004a) to the Ten Commandments of the Hebrew Scriptures to the theories of Sigmund Freud to the most recent updates of the American Psychological Association's Diagonistic and Statistical Manual of Mental Disorders, evidence attests to the omnipresence of lies amid human communities. Until recently, discussion about the signs of deception and the workings behind it could only rely upon external evidence.
For example, the polygraph machine, more commonly known as the 'lie detector,' can only monitor changes in pulse and breathing rate, perspiration, and blood pressure that correlate with anxiety (Knight 2004), a supposed consequence of the emotion of 'guilt' considered to accompany deception. This method of detecting and evaluating deception lacks fundamental credibility, as it relies upon physiological changes that only correlate with the telling of lies, allowing no conclusions to be made about deception's source itself: the brain.
Without reliable access to the cells of a nervous system whose staggeringly complex patterns of firing underly every human behavior, the sharp delineation of 'lie' from 'truth' remains beyond grasp. Only in the past decade, with the introduction of fMRI, has bridging the chasm between our selves and our minds in order to learn the true nature of deception entered the realm of possibility. Theorizing a bridge and building a bridge, however, remain separate tasks. Current research cannot yet support the clinical definition or detection of deception with fMRI.
The primary advantage of fMRI that has permitted its success is its ability to non-invasively observe patterns of neuron activation in the entire brain with unprecedented resolution and accuracy. Unlike previous dynamic imaging techniques, which required the injection of a radioactive contrast agent and were thus limited in the number of scans they could perform without harmful overexposure to radionuclides for the subject (DiGirolamo 2001), fMRI collects data from entirely natural bodily processes. When a neural region becomes relatively more active due to sensory or cognitive stimulation, the neurovascular system increases oxygenated blood flow to the region in question to aid the neurons' hightened metabolism.
This oxygenated blood possesses different magnetic properties from deoxygenated blood. When the spins of the hemoglobin nuclei aligned to the magnetic field are disturbed by a burst of radio waves, they release measurable electromagnetic signals as they return to their original alignments, a process called precession. Deoxygenated blood contains differently structured hemoglobin than oxygenated blood, so its precession appears at a different frequency from that of its oxygenated counterpart. Thus, fMRI dynamically identifies neuronal activity by detecting the regional changes between oxygenated and deoxygenated blood—blood oxygen level-dependent (BOLD) measurement (DiGirolamo 2001).
Knowing only the locations of activity in the brain during stimulation, though interesting, is insufficient for the study of complex behaviors such as deception. Skeptical scientists have challenged the utility of locational data derived from fMRI, with the extremes of criticism charging fMRI of being a mere sophisticated rehashing of the pseudo-scientific observations of phrenology popular in the late 19th and early 20th centuries, which purported to measure the bumps of the skull associated with various 'regions' of the mind that supposedly indicated certain personal and social qualities (Donaldson 2004).
A properly designed experiment using fMRI, however, does not just identify 'where' activity is occurring. It can also answer 'why' the activity is occurring. Proper temporal measurement of activity can identify functional differences in the role an activated region plays in a cognitive process. Separating trial-related processing, represented by a 'spike' in activity, from task-related processing, represented by a sustained elevation of activity, allows experimenters to 'parse' the patterns of regional activation they identify, giving a multi-dimensional structure to their observations. By both 'mapping' and 'parsing' the brain, reliable conclusions about the role of a particular region of the brain in a cognitive process may be drawn, and even expanded on to include the interactions and comparisons of multiple regions that are the standard for complex behaviors such as deception (Donaldson 2004).
fMRI investigation into 'truthful' and 'deceptive' neural activation patterns
Mixed measurements combining locational, temporal, and intensity data allowed the first glimpses into the mechanics of deception. A study conducted by Spence and others (2001) examined the inhibition of 'truthful' responses theoretically necessary for lying. Twenty-three subjects were asked questions by a computer in the presence of an investigator to which they responded with an affirmative or negative answer by pressing the respective computer key. In addition to the questions, the computer presented a color code unknown to the investigator that informed the subjects whether they should lie or tell the truth. Each question was presented twice, in order to compare neural activity for both truthful response and deception.
The results of the experiment demonstrated a greater activity during the telling of 'lies' in the bilateral, ventrolateral, prefrontal, and anterior cingulate cortices of the brain, areas implicated in the inhibition of immediate responses, with no comparable greater activation during the telling of 'truths.' In addition, Spence and others identified a ca. 200 ms delay for a deceptive response in comparison to a truthful response for subjects questioned both within an fMRI scanner and without. This implies that truth telling is a 'baseline' activity, with the telling of lies associated with greater activation, suggesting the involvement of executive function, a category of cognitive function that includes behavior initiation and inhibition, problem solving, and the manipulation of useful data stored in conscious working memory.
A subsequent study by Langleben and others (2002) confirmed truth-telling as a baseline activity and noted specific patterns of neural activation identifiable with deception. The team hypothesized that fMRI could detect neural correlates specific to deception by increased activity in the anterior cingulate cortex, the superior frontal gyrus, and the left premotor, motor, and anterior parietal cortex—areas associated with executive control.
The experiment made use of the Guilty Knowledge Test (GKT), a method of interrogation by polygraph to detect whether a suspect possesses incriminating knowledge of crime scene details that has been adapted to psychophysiological research in the lab. Subjects were presented with a series of cards and asked questions about their content, with 'Truth,' 'Non-Target,' and 'Lie' cards asking whether the subject possessed the card shown (Non-Target response was negative), and one 'Control' card (the Ten of Spades) asking whether it was the Ten of Spades, in order to combat habituation.
Two clusters of significant BOLD signal increases were identified with deception in the results, located in the areas of the right superior frontal gyrus and the prefrontal to dorsal premotor cortex, including the anterior parietal cortex. No areas showed significant decrease in activity. Once again, no comparable increases were identified with truthful responses, providing further evidence for truth-telling as a baseline state. The regions identified with deception confirmed an fMRI detectable neurophysiological difference between deception and truth at the brain activation level.
Mechanics and limitations of identifying deception with fMRI
Although the 2002 study of Langleben and others identified where activation during deception occurs, and thus demonstrated an observable difference between telling a lie and telling a truth, they did not address how this difference arises. Another review led by Spence and others (2004a) sought to clarify this point, theorizing that deception was an executive function. Executive functions may access awareness, but they do not necessarily have to be conscious. Nonetheless, executive functions predicate increased activation as detected by an fMRI, traceable to the prefrontal cortex region of the brain.
The correlation between deception and BOLD signal detections within the prefrontal cortex across multiple studies (Spence 2001, Langleben 2002) suggests that deception belongs to the category of executive function, requiring among other tasks the inhibition of truthful response.
The discovery and confirmation of specific regions within the brain activated by deception might tempt interpretations of the data as means to root out lies from truths, but important distinctions must be drawn between identifying and detecting deception in the human mind. In a study seeking to replicate and improve upon the neural correlates of deception identified by Langleben and others (Kozel 2004), researchers found both discouraging and encouraging results.
Though a higher MRI field strength of 3.0 Telsas revealed heightened activation correlates through statistical analysis of the study group as a whole, the findings were not significant enough to isolate deception at the level of the individual. In other words, the results could positively identify five regions of the brain associated with deception across a range of ten subjects, but no single subject showed an activation pattern consistent enough to allow researchers to draw conclusions about the neural correlates of deception at the individual level.
Researchers were also unable to identify a specific cause for the variation across subjects. Unless this extensive individual variability were reduced, the activation patterns observed at the group level could not be used to detect deception. Advances in the fMRI study of basic deception, though considerable, do not yet offer a new 'lie detector' for practical use.
Individual variability is not the only factor complicating the application of fMRI to the identification and detection of deception. A study by Ganis and others (2003) sought to challenge the assumption that there is only one type of deception associated with one set of neural correlates. For this purpose, the experimenters directed participants to answer questions about matters like work experience or a family vacation deceptively, not only with spontaneously produced answers, but also with previously-memorized content. They theorized that lies memorized in advance would rely upon brain regions associated with episodic memory, the recollection of specific experiences, while spontaneous lies would rely upon regions associated with semantic memory, the recollection of abstract knowledge.
Their results confirmed that the neural activation patterns were modulated by the type of lie subjects were telling, with spontaneous lies accessing the bilateral superior and cerebellum region in addition to the right cuneus (associated with the retrieval of visual imagery). The only significantly greater activation associated with pre-memorized scenario lies occurred in the right inferior Brodmann area 10, associated with the retrieval of episodic memories.
The preponderence of fMRI data analyzing complex cognitive processes over the past half-decade has confirmed an identifiable pattern of neural activation associated with deception in a laboratory situation. Significant limitations and deficits of understanding still stand between these discoveries and their application to 'lie detection.' Importantly, studies thus far have not detected any specific pattern of activation signifying 'truth,' only that higher activation correlated with certain regions of the brain accompanies deception. Statistical power cannot currently isolate this data to the individual level, nor can it reveal any information beyond the scope of current experimental conditions, which have drawn a simplistic and somewhat artificial distinction between 'lie' and 'truth' that may not hold in a real world situation (Spence 2004a).
The addition of practical concerns such as the relatively high cost of obtaining fMRI measurements and the delicate calibrations necessary to ensure no outside factor such as excess movement contaminate a scan ensures that the use of fMRI as a tool to detect deception remains currently infeasible, though future research may eventually allow the possibility (Robinson 2004).
A further clinical usage of fMRI in the diagnosis of hysteria disorders in which subjects feel their limbs to be paralyzed though no physiological damage hinders movement has been suggested (Spence 2004b), however this too is currently beyond reach. No study has yet taken into account the factors that could distinguish feigned physical symptoms from those associated with the psychological condition of conversion disorder—for example, the added factors of anxiety, neurological changes that might be associated with pathological lying or other mental conditions that could encourage malingering (Spence 2004a).
Worth final consideration concerning the use of fMRI to define or detect deception is the issue of neuroethics. Deception, as a behavior with complex moral implications, is a territory fraught with hazards in defining what is 'normal' or 'abnormal' brain patterns and what these physiological signs imply about the individual in question (Illes 2003). Being asked questions of moral or judgemental nature while monitored by a machine that 'reads your thoughts' could be a significantly distressing experience for many.
Detecting deception in the court of law invites complex questions of legality. Is forced testimony analyzed by an 'infallible' lie detector a violation of the Fifth Amendment, prohibiting coerced self-incrimination? (Robinson 2004). And what would be the standards of admissibility for fMRI evidence in court, taking into consideration the individual variation inherent to patterns of neural activation? With these concerns in mind, it seems that recognizing and publicizing the current weaknesses of fMRI analysis of deception as well as its successes is important for maintaining an accurate public awareness of the capabilities of fMRI to explain the complex workings of the human mind.
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