Gray proposed that personality is rooted from two neuropsychological systems that control behavior and emotions. One of the two systems is the behavioral activation system (BAS), which functions on the concept of positive reinforcement. Previous research has indicated that the mesolimbic dopaminergic pathways are responsible for the activation of BAS and sensitivity to the construct produces heightened reward from positive reinforcement. As such, prior studies have demonstrated similar correlations between high BAS sensitivity and low P300 amplitude as a precursor for psychopathological disorders, due to reward dependency. The present study used the Carver & White (1994) questionnaire to obtain the BIS/BAS scales of 9 healthy, introductory psychology students. The event-related potential was an oddball paradigm of high frequency, low frequency and novel tones and P300 averages were extracted from an EEG. The low and high BAS scores both produced similar amplitudes, however the low scores produced a shorter latency. The results indicate inconsistency and emphasize the need for further scientific research to expand on theoretical constructs, such as personality.
Introduction
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Historically, the construct of personality was developed based upon philosophical principles that sought to explain the human psyche. As the theories of personality have become a major part of ‘mainstream’ psychology today, the biopsychological components of personality have evolved into an innovative area of scientific research. Gray (1987) argued that personality is influenced by the two brain systems that control behavior and emotions. A component of this theory, the behavioral activation system, is portrayed as a personality construct with a neurological foundation. A neuropsychological paradigm is crucial in the deconstruction of theoretical hypotheses to influence the expansion and application of knowledge regarding human behavior. The use of electroencephalograms with event-related potentials and personality questionnaires regarding the behavioral activation system emphasize the importance for exploring theoretical constructs with scientific research.
Based on research from animal learning paradigms, Gray’s (1993) personality theory asserts the idea that individual differences in personality traits mirror the variability in sensitivity towards stimuli affiliated with negative and positive reinforcement (Franken et al., 2006). The behavioral activation system is a neurological reward mechanism that is initiated by positive reinforcement. It mediates responses to signals of conditioned reward, non-punishment, escape from punishment and the activation influences progression toward goals (Harmon-Jones & Allen, 1997). The opposite emotional system is the behavioral inhibition system; which is activated by conditioned stimuli associated with punishment or the termination of reward (Franken et al., 2006). That being said, the behavioral activation and inhibition systems are extremes of a continuum in which one’s behavior is likely to be reinforced positively or negatively, depending on which part of the continuum they score.
The behavioral activation system (BAS) is connected to positive feelings and approach behaviors when experiencing a reward (Gable et al., 2000). For example, an individual with high BAS sensitivity would seek out everyday type situations where they experienced positive reinforcement, or search for similar situations where they have a chance of being positively reinforced. Positive reinforcement is how people thrive in the world. From an evolutionary perspective, to go out and hunt for food when experiencing hunger, find food and bring it home to eat and share with family members so they can survive is an example of everyday positive reinforcement. The key difference between a typical situation and a situation in regards to an individual with high BAS sensitivity would be that the positive reinforcement would be differentially reinforced more so in comparison to conventional reinforcement (Franken et al., 2006).
Gray’s (1993) theory of personality suggests that those with high behavioral activation sensitivity are predisposed to psychopathological disorders due to their perceived response from positive, differential reinforcement (Franken et al., 2006). That being said, impulsivity is a key characteristic of high BAS sensitivity and is a major variable in the susceptibility of risky behavior. Other correlations to high sensitivity are high psychoticism, neuroticism and extraversion, which demonstrates that high BAS sensitivity, could act as a precursor for delinquency among the population (Jorm et al., 1999).
Neuroscience is beginning to identify strong relationships between BAS sensitivity and approach behaviors such as; conduct disorder, alcoholism, substance abuse and psychopathy. According to Gray (1993), the biological basis of BAS is associated with mesolimbic dopaminergic pathways ascending from nucleus A10 of the ventral tegmentum of the brainstem (Matthews & Gilliland, 1999). Recent studies involving substance use indicate the similarity between dopamine release in the nucleus accumbens and the emotional high observed in alcohol and drug users. Thus, implying that BAS sensitivity and is related to addictive behaviors and substance abusers have an increased responsiveness to stimuli associated with rewards (Franken et al., 2006).
Sutton and Davidson (1997) claim that throughout various clinical and laboratory observations, the left prefrontal cortex is a biological substrate of approach behavior and positive affect; whereas the right prefrontal cortex exhibits the opposite behaviors, imposing the locality of the behavioral inhibition system. When damaged, the left prefrontal cortex influences depressive symptomatology due to the inhibition of approach behaviors (Sutton & Davidson, 1997).
More specifically, the reward signal begins with increased dopamine cellular activity in the ventral tegmental area, which labels environmental stimuli with appetitive value and appears to signal motivating events (Kalivas & Nakamura, 1999). The glutamatergic input from the amygdala and afferents cue behavior if the stimulus is a conditioned reward. The nucleus accumbens and afferents to the nucleus accumbens serve distinct functions involving motivational circuitry, which would reinforce the behavior. The major neurotransmitters involved in the motivational circuitry are GABA, glutamate and dopamine, however; encephalin, serotonin and acetylcholine are also present. Finally, afferents from the prefrontal cortex integrate information from short-term memory into a behavioral response (Kalivas & Nakamura, 1999).
To explore theories of previous research regarding brain localization and processes of BAS, a method of measuring cortical activation could be initiated, such as an event-related potential with an electroencephalogram (EEG). Event-related potentials (ERPs) are a non-invasive method of measuring brain activity during cognitive processing (Johnson et al., 1987). ERPs are linked in time with a physical or mental event and are extracted from an EEG by means of signal averaging (Duncan et al., 2009). The transient electric potential shifts are time-locked to the stimulus onset; such as the presentation of a word, sound, or image. Each component reflects brain activation associated with one or more neurological operations. In contrast to behavioral measures, such as error rates and response times, ERPs are characterized by simultaneous multi-dimensional online measures of negative or positive polarity, amplitude, latency, scalp distribution and its relation to experimental variables (Duncan et al., 2009). Thus, ERPs are beneficial and can be used to differentiate and aid in the identification of psychological and neural sub-processes involved in complex cognitive, motor or perceptual tasks (Nijs et al. 2007). An electroencephalogram (EEG) precisely measures these shifts in polarity with a distribution of electrodes placed on the participant’s scalp (Duncan et al., 2009).
The most analyzed component of the event-related potentials is at the p300 wave. Peaking as early as 250ms or as late as 900ms, the p300 is emitted by the brain when the participant recognizes and processes and incoming stimulus (Coles & Rugg, 1995). It is usually elicited using the oddball paradigm in which low-probability target items are mixed with high-probability non-target items. The latency between stimulus and response is the ‘stimulus evaluation time’ and is controlled by the pace in which the subject can place the stimulus into the correct category and respond (Coles & Rugg, 1995). The amplitude of the p300 depends on the probability of the target stimulus, and in an oddball paradigm, the rarer the event; the larger the amplitude will be of the p300 (Coles & Rugg, 1995). The amount of information processed also influences the amplitude suggesting that the p300 reflects a process in which the incoming information modifies and updates the current model of the environment (Coles & Rugg, 1995).
The p300 is divided into two components: the P3a and the P3b. The P3a is elicited over the frontal regions of the scalp and is represented as a positive component. The P3a occurs when a third ‘novel’ stimulus is incorporated into the simple oddball structure and has a shorter latency than the p300 (Johnson et al., 1987). The P3b is then defined as the classical p300, which is distributed over the centro-parietal area.
The behavioral activation system has three subscale components: reward-responsiveness, fun seeking and drive. The reward system and brain structures hypothesized in previous studies provide a strong argument in regards to BAS. Increased levels of dopamine and high BAS scores should be significantly correlated, as the function of dopamine involves increasing the readiness to discover new experiences. As such, it should also be appreciated that norepinephrine was not included as a key player in the neurotransmitters involving the reward system. One would assume that dopamine and norepinephrine would go hand in hand in regards to reward, as norepinephrine is the major neurotransmitter involved in motivation (Franken et al., 2006).
A study by Nijs et al. (2007) was conducted on 50 healthy, adult individuals using the Carver and White (1994) questionnaire and a visual oddball paradigm with averaging from an EEG. Previous studies incorporating BAS scores and extracting ERP averages from an EEG were unknown to Nijs et al. (2007), however they predicted a negative correlation between BAS scores and the p300 amplitude for their study. They did address the reoccurring theme in previous research of a low p300 amplitude and impulsivity, psychopathy and substance use disorders. The results of the study demonstrated significant positive correlations were found between BAS and p300 amplitude (Nijs et al., 2007). Therefore, the hypothesis for this study is that those with high BAS sensitivity scores will produce large p300 amplitude to the rare stimulus, because of the P3b’s indication of low activity in those with psychiatric disorders.
Methods
Sample
Participants for the study were recruited from introductory to psychology classes. They were given the option of writing a paper or volunteering for a study involving personality in the research lab and receiving credit compensation. Those who volunteered for the study were informed that if they were on medication or had medical conditions that conflicted with EEG results, then they would be discharged. This research study initially began with a total of twelve introductory to psychology students; however, adequate data was only retrieved from nine participants.
Instruments
An online version of the Carver and White (1994) Behavioral Inhibition System and Behavioral Activation System Questionnaire was completed by each participant prior to the study. This questionnaire is the latest BAS/BIS updated measurement questionnaire involving the three subscales of BAS (reward responsiveness, drive and fun seeking). Upon arrival, a medical form was filled out to give an indication of health status and a consent form was distributed and signed. A type of oddball paradigm was utilized and an electroencephalogram (EEG) recorded and averaged the corresponding event-related potentials.
Procedure
After receiving the completed questionnaires, the total scores were then calculated. Those students participating in the study were given an outline of the regulations and procedures of the experiment. Upon entering the research laboratory, the medical and consent forms were filled out before commencing the study. Participants were then connected to the EEG using the Jasper 10-20 placement, which particularly involves the electrodes Fz, Cz, Pz and reference electrodes behind the ears. Electrodes were also placed under the right eye and the ground electrode on the forehead to identify muscle activity that might be confused with brain activity. The student was then directed into an isolated room where they received headphones and were presented with the oddball paradigm. In random sequence a rare low frequency tone, high frequency tone and a novel tone were administered. The participants were made aware that when the target low frequency tone was presented they needed to respond by clicking a button. Once all stimuli were executed, participants were disconnected from the EEG instruments and the data obtained was explained. Any questions the participants had were answered and credit compensation was then provided.
Results
Those who scored high in behavioral activation system on the Carver and White (1994) questionnaire showed small P300 amplitude. P300 amplitude also highlighted a positive correlation in regards to the rare stimulus: as BAS scores increased, P3b amplitude increased. The high BAS scores produced a longer latency on the P300, in comparison to the low BAS scores.
Those who scored low in behavioral activation system had similar P300 amplitudes indicating a non-significant result among averages of the two groups. Those who scored low in BAS also exhibited a significantly shorter latency, meaning they were quicker to respond and categorize the incoming stimuli.
Table 1. P3 amplitude and latency scores for high and low scores on BAS personality trait.
Figure 1. Average of high and low BAS scores extracted from Pz component of EEG electrode using oddball paradigm ERP.kathleen curtis Graph averages P3 High and low.jpg
Discussion
The present study hypothesized that higher BAS scores would produce large P300 amplitude. The results showed inconsistency, as there is not a significant difference among those who scored high and low on the behavioral activation system scale in this study. The amplitudes at Fz, Cz and Pz were all relatively small and similar among low and high BAS scores. The significant data found in the results was the latency differences between high and low scores. Each electrode produced a significantly different result with the lower scores having shorter latencies. Those who scored higher on the Carver & White (1994) BAS questionnaire respond slower to the evaluation of stimuli than those who scored lower.
As both low and high scores generated similar amplitudes, generalizing previous studies of high BAS sensitivity and low P300 amplitude should be cautioned. The sample size of this study was small; therefore further research should increase this to obtain a more representative sample. The age of participants is also a factor that should be taken into consideration for this study, as alterations in behavioral activation and inhibition scores have been known to occur with time. The gender of the participants is a variable that should be recognized for future research as personality and gender could be interrelated. Also, the accuracy of the participant’s performance on the online questionnaires is a limitation for consideration and the stimuli may also not represent a true portrait of the construct.
Both theoretical and neuropsychological explanations contribute the greatest understanding of constructs in psychology, such as personality. This is evident among the research conducted that involves the behavioral activation system. These advancements allow for the expansion and application of such knowledge to situations that have the potential to better society. For example, awareness of the behavioral activation and inhibition systems could aid the education systems to develop curriculum that is more suitable to the individual. Also, more intensive BIS/BAS measurements could potentially identify children/youth at risk and induce the early on set of proactive measures. It is obvious the possibilities are endless when the latest technology brings together science and theory.
