To examine both the lateralisation of motivational processes and the BAS as a key player in this process, the present research examined BAS levels among participants, and attempted to manipulate cortical activity before measuring approach motivation. Approach motivation has many conceptualisations. However, previous research does not dictate that any specific concept would not be affected by the independent variables of this methodology. Therefore, a questionnaire was used which measures two concepts of motivation (intrinsic and success) in an attempt to gain as complete a picture as possible of any affects of the independent variables. For the first independent variable, a measure of BAS was taken, and high BAS individuals were hypothesized to demonstrate higher scores of approach motivation generally, as would be consistent with previous research (Elliot and Thrash, 2002). Additionally, the present research looked to manipulate cortical activity by using Harmon-Jones’ (2006) hand-contraction task to direct hemispheric activation as a second independent variable. This was followed immediately by administration of the measure(s) of approach motivation. Participants were hypothesized to produce higher scores on the measure of approach motivation after squeezing with their right hand than with their left, indicating they felt more motivated towards an upcoming task. This would be consistent with previous research which demonstrated asymmetry to predict motivational direction (Sutton and Davidson, 1997). Finally, an interaction between these two factors was hypothesized. Preliminary findings have demonstrated an association between stable differences in asymmetrical activation and individual differences in natural levels of approach motivation (Richard, 1992). This led to the hypothesis that an effect of natural level of BAS sensitivity and activation of the left hemisphere would be demonstrated on scores of intrinsic and success motivation.
The experimental design was a two-condition mixed design. The between-participants condition was trait BAS, with two levels, high and low, which were identified using Carver and White’s BIS/BAS Scale. The within-participants condition was hand contraction, with two levels, left and right. The dependent variable was subjective experience of approach motivation, measured using a shortened version of the Dundee Stress-State Questionnaire called the Shortened Stress-State Questionnaire. The Shortened Stress-State Questionnaire contains two conceptualisations of motivation, and separate statistical analyses were used for these.
Participants were recruited using an opportunistic sample. Only university undergraduate students or graduates took part in an attempt to standardise intelligence. A total of 20 (10 males) individuals participated whose ages ranged from 19 to 45 (M = 31.9, SD=6). Left-handed individuals were excluded from participation to control for hemisphere specialisation. Recruitment was based on voluntary willingness to participate when approached by the experimenter and no compensation was awarded.
Participants were administered Carver and White’s BIS/BAS scale to identify natural levels of BAS sensitivity. This scale has been used in several empirical studies and has been shown to have good reliability and validity (Elliot and Thrash, 2002). For the purposes of the present experiment, only the measure of BAS (and not BIS) held relevance, and thus only the 13-items from the BAS scale (e.g., ‘I go out of my way to get things I want’) were included. These items produced a BAS score, which were divided into ‘high’ and ‘low’ categories using a median split. A shortened version (15 items) of the Dundee-Stress State Questionnaire, called the Shortened Stress-State Questionnaire (SSSQ), was used to measure approach motivation (Matthews et al, 2002). The SSSQ has also been widely used and found to have good validity and reliability (Helton, 2004). Approach motivation is a highly debated concept, and many different conceptualizations have been suggested. Past research has not suggested that either the BAS or left hemisphere specialisation are limited to specific conceptualisations. The SSSQ employs two conceptualisations of motivation. Intrinsic motivation (e.g., ‘Doing the task is worthwhile’) and success motivation (e.g., ‘I am concerned about not doing as well as I can’) were both included in the present research, and were analysed separately. Other materials included a small soft ball to be squeezed during the hand-contraction exercise, and a stopwatch for monitoring the timing of the contractions.
Participants were tested individually, in a quiet space. The hand which they contracted first was counter-balanced to avoid potential order effects. Upon arrival for the first condition, they were supplied with limited information pertaining to the nature of the experiment. It was described that they would ‘be asked to fill out questionnaires and participate in a muscle activation task’ (See Appendix). Participants were instructed that all questions would be answered after completion of the experiment, to avoid questions which could jeopardise standardisation. After providing informed consent, they were provided with Carver and White’s BIS/BAS scale. Directions for completion were presented on the questionnaire. After finishing the BIS/BAS scale, participants were directed, by experimenter script, to take a ball supplied by the experimenter in the appropriate hand, as dictated by experimental condition. The participant was asked to ‘squeeze the ball as tightly as you [sic] can for forty-five seconds, and then rest for fifteen seconds for a total of five minutes’. It was explained that the experimenter would ‘monitor the time and direct the exercise’ and that they should ‘relax, look strait ahead, and pay attention to the feelings and sensations you [sic] experience while squeezing the ball’ (See Appendix). These instructions were a replication of those used by Harmon-Jones (2006) when he successfully employed the same task to direct hemispheric activation. The experimenter used a stopwatch to time the task, and gave standardised instructions to ‘begin squeezing’ and ‘rest’ at the appropriate intervals.
After completion of the ball-squeezing task, participants were provided with the Shortened Stress-State questionnaire to measure their subjective feelings of approach motivation towards a final task. The questionnaire informed them that ‘the last task of the experiment will take place after completion of this questionnaire’ and that they would ‘be given instructions on the last task after the following questions have been answered’ (See Appendix). Scripting of these instructions was key in attempting to insure participants knew a standardised amount about the final task. It is probable that participants completing the second condition of the experiment would have had a prediction of the upcoming task and this may have influenced their attitude towards it. However, counterbalancing attempted to negate affects of assumption and subsequent attitude change. After completion of the Shortened Stress-State Questionnaire, participants underwent a dummy digit-span task, as the SSSQ referred to an upcoming task and the within-participants design required a task took place. They were instructed that the experimenter would now ‘read aloud a series of numbers’ and that the participant should repeat the digits after completion of each sequence. The experimenter began with a two-digit sequence and one digit was added to the next sequence until the participant made a mistake. Once finished, the first condition of the experiment was complete. The second condition began with the ball-squeezing task in the hand which had not been used in the first condition. Participants were instructed using the same script employed in the first condition and the exercise was undergone with the same procedure. The rest of the experiment was carried out identically to the first condition. After completion of the digit-span task, participants were fully debriefed and all questions were answered. The first segment of the procedure took approximately fifteen minutes, and the second half approximately ten minutes.
All participants’ scores were included in the analyses as there were no outliers and no indication that any participants had not completed the experiment correctly and to their best ability. A median split was performed on scores of BAS to split participants into two groups: high and low. Table 1 displays the means and standard deviations for these groups. Preliminary analyses provided the means and standard deviations for all conditions, which are displayed in Tables 2 and 3. Additionally, t-tests were employed to investigate possible order effects, despite counterbalancing, and yielded no significant effect of order within any condition. Scores on the digit-span dummy task were analysed using t-tests, and no significant results were found
Table 1. Total BAS Scores on SSSQ after Median Split
Table 2. Means and (Standard Deviations) of Intrinsic Motivation
Table 3. Means and (Standard Deviations) of Success Motivation
Two 2x2 mixed factorial ANOVAs were run to analyse the data. A 2 (BAS level) x 2 (hand contraction) ANOVA was performed using scores of intrinsic motivation. A significant main effect of BAS level was demonstrated F(1,18)=5.14, p<.05. However, a significant main effect of hand was not observed, nor was a significant interaction. Figure 1 illustrates the significant main effect of BAS level.
A second 2 (BAS level) x 2 (hand contraction) ANOVA was performed to analyse effects on success motivation. A significant main effect of hand was observed F(1,18)=7.04, p<.05. However, a significant main effect of BAS level was not observed. Additionally, a significant interaction was not observed, but means were in the expected direction. Figure 2 illustrates the significant main effect of hand.
The results demonstrated mixed support for the hypotheses. Effects were found of BAS strength and of hand contraction, but only within isolated conceptualizations of approach motivation. Success motivation was found to be significantly affected by the hand contraction task, with participants demonstrating significantly higher scores of motivation after contractions with their right hand, as was consistent with the hypotheses. Intrinsic motivation was found to be significantly affected by BAS level, with high BAS participants producing significantly higher scores of motivation than low BAS participants, as was also consistent with the hypotheses. A significant interaction was not demonstrated, although the lack of significance could have been a problem of low statistical power. Due to time constraints, a larger sample size was not possible but would have been preferable to increase power. Additionally, use of a median split may have reduced power in the BAS conditions. A multiple regression may have been preferable had the sample size been larger. Despite the lack of a significant interaction, results somewhat conform to expectations set by previous research. In the present research, two concepts of approach were employed. Previous research has lacked conceptual specificity regarding potential effects of the BAS or the left hemisphere on motivation. The fact that the independent variables had such differing effects on intrinsic and success motivation is interesting, and could inform future research. Despite potential issues with the concept of approach and how this is mediated within the BAS and the left hemisphere, results provided general support for the motivational direction hypothesis. The present research was able to demonstrate a relationship between natural levels of BAS, the lateralization of motivational processes, and approach motivation itself.
It is possible that methodological issues played a key role in the non-significant results. Although the hand-contraction task produced a significant manipulation of success motivation, a manipulation check after this task would have been useful. Additionally, a base-rate measure of approach motivation could have clarified shifts in motivation taking place due to the hand-contraction task, or pre-existing as an effect of BAS levels. More general randomly acting variables could also be addressed by future research, such as the use of psychology students as participants, who may have been familiar with the materials being used, potentially jeopardizing methodological validity. The participants were also personally acquainted with the experimenter, which could have affected questionnaire responses despite the assurance of anonymity. Thirdly, the experimenter was not blind to the conditions, potentially introducing experimenter effects. Finally, although the environment of testing was similar for all participants and conditions, standardization of test location could have improved the methodology.
Methodological issues may not have been the only contributor to null results; theoretical issues could also have played a role. It has only been identified that high BAS will increase motivation towards goal-directed tasks, and possible limitations to certain conceptualizations of motivation has not been extensively explored. The lack of a significant effect of BAS level on success motivation in the present research could indicate a theoretical flaw in the modern understanding of the BAS as a mediator of general approach motivation. Additionally, the lack of a significant effect of hemispheric activation on intrinsic motivation could signal a conceptual flaw in the understanding of lateralization of motivational direction. The motivational direction hypothesis of hemispheric activation does not specify limitations in the types of lateralized motivation (Petersen et al, 2008). If approach motivation is understood to be generated through activity in the left hemisphere, it is possible that there is a distinction between which types of motivation are housed there. It could be that intrinsic motivation is in some way qualitatively different from other types of motivation, and within this qualitative distinction, lateralization is not as strong.
Despite some limitations, this research is useful to future exploration of both the BAS and its location in the brain. Within BAS research, the results presented here offer future research the opportunity to examine the BAS as an approach mediator. Different conceptualizations of approach could be used to further tease apart the functions of the BAS. This would be especially important if the present results were shown to be consistent across replications of the methodology. Additionally, running the same procedure using an EEG could provide an illustration of the neural activity of high and low BAS individuals, and allow researchers to explore differences between these groups. An EEG could also provide further insight into the lateralization of the BAS and the division between right and left hemisphere control of motivation. Additionally, if the mixed results demonstrated within this research are consistent even when future research can eliminate some of the aforementioned methodological weaknesses, there could be implications of the concepts of both trait BAS and the motivational hypotheses of lateralization. Going forward, as the understanding of motivation is expanded, research could combine these growing fields of research and use the knowledge gathered between these aspects to expand both areas of research. Adaptations and extensions of this research could prove to be beneficial to individual differences research, neuropsychology, and the understanding of motivational processes.
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