Pure correlates of exploration and exploitation in the human brain

Balancing exploration and exploitation is a fundamental problem in reinforcement learning. Previous neuroimaging studies of the exploration–exploitation dilemma could not completely disentangle these two processes, making it difficult to unambiguously identify their neural signatures. We overcome this problem using a task in which subjects can either observe (pure exploration) or bet (pure exploitation). Insula and dorsal anterior cingulate cortex showed significantly greater activity on observe trials compared to bet trials, suggesting that these regions play a role in driving exploration. A model-based analysis of task performance suggested that subjects chose to observe until a critical evidence threshold was reached. We observed a neural signature of this evidence accumulation process in the ventromedial prefrontal cortex. These findings support theories positing an important role for anterior cingulate cortex in exploration, while also providing a new perspective on the roles of insula and ventromedial prefrontal cortex.     

Effects of reducing attentional demands on performance of reading comprehension tests by third graders

The researchers examined the effects of reducing attentional demands on reading comprehension test scores. Third grade students (N=939) completed two forms (T & S) of the Stanford 9 Reading Comprehension Test (54 items, 50 min.) in the spring of 1999. Form T (state-mandated) was administered following standardized procedures in one session. Form S (alternate) was administered in multiple, divided-time sessions, that is, the total test time and items were divided in halves and thirds per session to lessen attentional demands. A repeated-measure analysis of variance yielded significant effects for average and low readers. A resource match explanation and a metacognitive explanation are offered for the results, and educational implications are discussed.     

THE EFFECT OF THE ABSENCE OF CLOSE SUPERVISION ON THE USE OF RESPONSE COST IN A PRISON TOKEN ECONOMY1

A naturally occurring experiment, in which direct supervision of a token economy in a penal system was removed and re-instated, is reported. A retrospective analysis revealed that in the absence of close supervision the use of response cost rose dramatically, both in terms of categories of behaviors for which response costs were levied and in the frequency of their use. The return of direct supervision led to a decreased use and an end to the growth of categories of behaviors punished.     

Psychophysiological responding as a function of age: The importance of matching

Few studies in the past which have employed psychophysiological measures have controlled for age. We have studied the effects of age on the heart rate, hand surface temperature, cephalic vasomotor response, and frontal electromyographic activity (EMG) of 73 normal individuals who varied in age from 18 to 68 years and were evenly divided into younger, middle, and older age groups. Comparisons were made between groups across eight conditions — baseline, relax body, warm hand, relax facial muscles, mental arithmetic, positive imagery, negative imagery, and cold pressor. Results indicated a direct linear relationship between age and electromyographic activity during relax facial muscles and mental arithmetic conditions. There was also a linear relationship between age and hand surface temperature during stressor conditions. Most important, significant interactions were found for both frontal EMG and heart rate measures with age. Post hoc analyses revealed differences on the frontal EMG levels between younger and older age groups during negative imagery, warm hand, and cold pressor conditions. Heart rate differences were found during positive imagery between the younger age group and the medium age group and during cold pressor between the younger age group and both the medium and the older groups. The implications of these findings are discussed.This research was supported in part by NINCDS Grant NS-15235.     

A comparison of the PAI and MMPI-2 as predictors of faking bad in college students

Both the Minnesota Multiphasic Personality Inventory-2 (MMPI-2; Butcher et al., 2001) and Personality Assessment Inventory (PAI; Morey, 1991) offer a large set of scales devoted to the identification of response styles. This study directly compared the effectiveness of the 2 inventories as indicators of overreporting. The 2 measures were administered to 52 college students instructed to fake bad under conditions describing either a forensic (n = 24) or psychiatric (n = 28) setting as well as to 432 psychiatric patients. Results indicated that the MMPI-2 F - K index and Fp Scale were the best single indicators of a faking bad response style and that the MMPI-2 scales were the better indicators as a set. However, the PAI scales demonstrated a significant level of incremental validity over the MMPI-2 indicators in every analysis conducted. The findings suggest that either inventory offers an effective approach to the detection of overreporting, and administering both inventories can enhance the accuracy of prediction further.     

The psychophsiology of aggressive drivers: comparison to non-aggressive drivers and pre- to post-treatment change following a cognitive-behavioural treatment

Twenty drivers were remanded to our treatment program by the courts following arrests related to serious aggressive driving behaviors. Ten additional drivers entered our program in response to our advertisements thus identifying themselves as aggressive drivers. Psychophysiological assessments were conducted on all 30 drivers and heart rate (HR), systolic and diastolic blood pressure (SBP and DBP), and skin resistance level (SRL) were measured in response to exposure to a mental arithmetic neutral stressor, two idiosyncratic, audio-taped, aggressive driving vignettes (audio 1 and audio 2), and one non-driving related fearful vignette. Fourteen non-aggressive driving controls also completed the assessment. The results indicated that the aggressive drivers (ADs) showed significantly more SBP responsivity during audio 1 and audio 2 and significantly less SBP reactivity during the mental arithmetic stressor than the controls. The aggressive drivers then completed a four-week, group intervention which included relaxation techniques specifically targeting aggressive driving behaviors. The same psychophysiological assessment was conducted at post-treatment. The results showed significant pre- to post-treatment decreases in HR, p<0.003, SBP, p<0.01, and DBP, p<0.02 during audio 1. Similarly, decreases were evident in audio 2 in SBP, p<0.03 only. No decreases in reactivity occurred during the neutral stressor or fearful situation.     

Perceiving words during reading: Lack of facilitation from prior peripheral exposure

As their eye movements were being monitored, college students read short texts displayed on a cathode-ray tube. As they read, the contents of certain word locations changed from fixation to fixation, alternating between two words differing in two letters. This manipulation had no effect on reading unless the subjects happened to regress to or reread the word later. The results indicated that these words, which were low in contextual constraint, were read only when directly fixated, and that there was no facilitation from prior peripherally obtained information about the words.     

On the Assessment of Situational Intrinsic and Extrinsic Motivation: The Situational Motivation Scale (SIMS)

The purpose of the present research was to develop and validate a situational (or state) measure of motivation, the Situational Motivation Scale (SIMS). The SIMS is designed to assess the constructs of intrinsic motivation, identified regulation, external regulation, and amotivation (E. L. Deci & R. M. Ryan, 1985, 1991) in field and laboratory settings. Five studies were conducted to develop and validate the SIMS. Overall, results show that the SIMS is composed of 4 internally consistent factors. The construct validity of the scale is also supported by correlations with other constructs as postulated by current theories. Moreover, the SIMS is responsive to experimental induction as evidenced by data gathered through a laboratory study. In sum, the SIMS represents a brief and versatile self-report measure of situational intrinsic motivation, identified regulation, external regulation, and amotivation.