Self-Perception of Extroversion Increases with Social Media Use: A Social Media Induction Task.

Previous studies have examined the relationship between social media and extroversion, often relying on correlational designs. This study introduced a social media induction procedure to examine the relationship between social media and extroversion with an experimental design. In a procedure adapted from the personality research literature, participants used a written prompt to imagine themselves as a social media influencer and were then asked to use social media with this mindset. Participants' extroversion was measured before and after this activity using the Big Five Inventory. The results show that this social media induction procedure resulted in increased reports of extroversion after the task, and this post-task change was not predicted by other related social media factors (such as hours of social media use per day). These results complicate the assertion that differences in social media use between extroverts and introverts are due to its stronger appeal to extroverts.

Health anxiety and attentional control interact to predict uncertainty-related attentional biases.

BACKGROUND AND OBJECTIVES: Current theories of health anxiety and a growing body of empirical literature suggest that those high in health anxiety symptoms might find uncertainty itself threatening and demonstrate attentional biases for uncertainty-related information (ABU). Moreover, a dual processes model of attention would suggest that individual differences in attentional control might modify such a relationship. The present study was designed to explore this proposed health anxiety-ABU relationship and also to consider attentional control as a moderator of theoretical and clinical relevance. METHODS: Undergraduate participants (N = 148) completed a self-report measure of health anxiety symptoms and two performance-based tasks to assess ABU and attentional control. RESULTS: Hierarchical regression analyses showed a significant interaction between health anxiety and attention control in predicting attentional disengagement from, but not engagement with, uncertainty-related words. Specifically, results of the simple slopes analysis suggested that those with elevated health anxiety symptoms and better attentional control may use top-down attentional control processes to disengage their attention from distressing uncertainty-related stimuli faster than those with worse attentional control. LIMITATIONS: The analogue sample is a study limitation. CONCLUSIONS: Results provide new insights into the nature of attentional biases within health anxiety. Results are discussed in light of recent work on attentional control and avoidance-based psychopathology.

Increasing cognitive load attenuates the moderating effect of attentional inhibition on the relationship between posttraumatic stress symptoms and threat-related attention bias variability.

Theory and empirical evidence suggest that those with higher posttraumatic stress (PTS) symptoms and better attentional control (i.e., the strategic control of higher-order executive attention in regulating bottom-up, stimulus driven responses to prepotent stimuli; Sarapas et al., 2017) can use that ability to disengage and shift attention away from threat stimuli and reduce threat-related attentional dysregulation (i.e., avoidance/overcontrollers). Those with relatively worse attentional control lack the requisite resources to do this, leading to prolonged attentional engagement with threat stimuli and threat-related attention dysregulation (i.e., maintenance/undercontrollers). Given that attentional control is a limited resource, strategic avoidance of threat information or reduced threat-related attention dysregulation may not be possible among those with relatively higher attentional control when cognitive load is relatively high. To test this hypothesis, the interaction between PTS symptoms, attentional control, and cognitive load was examined as a predictor of threat-related attentional bias and threat-related attention bias variability. Participants (N = 125 undergraduate students) were randomly assigned to high or low load conditions. Participants completed self-report measures of PTS symptoms, a behavioral measure of attentional control, and a novel task that assessed threat-related attentional bias via eye movements and threat-related attention bias variability via button press. The results of a series of hierarchical regressions showed that attentional control moderated the relationship between PTS symptoms and threat-related attention bias variability in the low, but not high, load condition. This moderation effect was not observed for threat-related attentional bias assessed via eye-tracking. Consistent with theory, under conditions of higher cognitive load, overcontrollers may not be able to use attentional control to consistently regulate threat-related attention. Study findings suggest that it may be important to consider contextual factors that increase cognitive load, as well as individual differences in attentional control, when developing attention bias modification interventions to reduce PTS symptomatology.

Individual differences in attentional control explain the differential expression of threat-related attentional bias among those with posttraumatic stress symptomatology and predict symptom maintenance up to one year later.

Individual differences in attentional control may explain null findings and inconsistent patterns of threat-related attentional bias (ABT) that are common in the posttraumatic stress disorder (PTSD) literature. At Time 1 (T1), trauma-exposed community participants (N = 89) completed a clinical interview, self-report measures, and an eye-tracking task developed to assess ABT. Participants completed follow-up assessments online 6 (T2) and 12 (T3) months later. Those with higher PTSD symptoms and deficits in attentional control exhibited a pattern of undercontrol, characterized by attention maintenance on threat and increased arousal. In contrast, those with higher PTSD symptoms and relatively better attentional control exhibited a pattern of overcontrol, characterized by threat avoidance and reduced arousal. These effects were specific to threat stimuli. Among PTSD symptom clusters, symptoms of hyperarousal were of central importance to the observed effects. Results from the longitudinal analysis indicate that both of these patterns of ABT are maladaptive, resulting in symptom maintenance at T2 and T3. These results have implications for (a) reconciling tensions between disparate models of ABT (i.e., vigilance-avoidance vs. attention maintenance), (b) precision medicine based approaches to targeting PTSD-related ABT, and (c) understanding the transdiagnostic role that attentional control may play in influencing ABT expression.

The BDNF Val66Met Polymorphism Moderates the Relationship Between Posttraumatic Stress Disorder and Trauma Script-evoked Attentional Bias to Cocaine Cues Among Patients with Cocaine Dependence.

There is extensive variability in cocaine-related attentional bias (AB) following trauma script exposure among cocaine-dependent (CD) patients with posttraumatic stress disorder (PTSD). Therefore, research is needed to identify the specific PTSD-CD patients most likely to exhibit an AB to cocaine cues. A common polymorphism in brain-derived neurotrophic factor (BDNF), Val66met, is associated with risk for stimulant addiction, and thus, was examined as a moderator of the association between PTSD and cocaine-related AB following trauma script exposure in this study. Adult CD patients with (n = 17) and without (n = 28) PTSD were exposed to a personalized trauma script, followed by a visual dot-probe task assessing cocaine-related AB. Task response times were used to examine traditionally calculated AB scores, as well as trial level bias scores (TL-BS) that more accurately model the temporal dynamics of AB. PTSD-CD patients homozygous for the BDNF Val/Val genotype exhibited greater bias for attending to cocaine-related stimuli following trauma script exposure than those carrying the Met allele. The PTSD by BDNF interaction did not predict response time variability on trials for which only neutral stimuli were presented, thus increasing confidence that the observed effect is specific to cocaine-related stimuli. PTSD-CD patients homozygous for the BDNF Val/Val genotype may be at particularly high risk for negative clinical outcomes (e.g., relapse, treatment dropout) as a function of prolonged attentional engagement with cocaine cues when exposed to trauma reminders.

Strength and Temporal Variance of the Default Mode Network to Investigate Chronic Mild Traumatic Brain Injury in Service Members with Psychological Trauma.

BACKGROUND: There is a significant number of military personnel with a history of mild traumatic brain injury (mTBI) who suffer from comorbid posttraumatic stress symptoms (PTS). Although there is evidence of disruptions of the default mode network (DMN) associated with PTS and mTBI, previous studies have only studied static connectivity while ignoring temporal variability of connectivity. OBJECTIVE: To assess DMN disrupted or dysregulated neurocircuitry, cognitive functioning, and psychological health of active-duty military with mTBI and PTS. METHOD: U.S. Army soldiers with PTS (n = 14), mTBI + PTS (n = 25), and healthy controls (n = 21) voluntarily completed a cognitive and symptom battery. In addition, participants had magnetic resonance imaging (MRI) to assess both static functional connectivity (SFC) and variance of dynamic functional connectivity (vDFC) of the DMN. RESULTS: Both the PTS and mTBI + PTS groups had significant symptoms, but only the comorbid group had significant decrements in cognitive functioning. Both groups showed less stable and disrupted neural signatures of the DMN, mainly constituting the cingulate-frontal-temporal-parietal attention network. Specifically, the PTS group showed a combination of both reduced contralateral strength and reduced unilateral variability of frontal-cingulate-temporal connectivities, as well as increased variability of frontal-parietal connectivities. The mTBI + PTS group had fewer abnormal connectives than the PTS group, all of which included reduced strength of frontal-temporal regions and reduced variability frontal-cingulate-temporal regions. Greater SFC and vDFC connectivity of the left dorsolateral prefrontal cortex (dlPFC) ↔ precuneus was associated with higher cognitive scores and lower symptom scores. CONCLUSIONS: Findings suggest that individuals with PTS and mTBI + PTS have a propensity for accentuated generation of thoughts, feelings, sensations, and/or images while in a resting state. Compared with controls, only the PTS group was associated with accentuated variability of the frontal-parietal attention network. While there were no significant differences in DMN connectivity strength between the mTBI + PTS and PTS groups, variability of connectivity was able to distinguish them.

Differential neural activation when voluntarily regulating emotions in service members with chronic mild traumatic brain injury.

The objective of this study was to characterize the functional activation of the neural correlates of voluntary regulation of emotion in soldiers both with and without chronic mild traumatic brain injury (mTBI). Using functional magnetic resonance imaging (fMRI) and a battery of cognitive and psychological health measures, we assessed differences between active-duty U.S. soldiers with chronic mTBI (n = 37) and without (Controls, n = 35). Participants were instructed to maintain (passively view), enhance, and suppress emotions associated with negative and neutral visual stimuli. The mTBI group showed significantly greater clinical symptoms, but only a mild decrement in attention. Group contrasts, while controlling for posttraumatic stress disorder (PTSD) symptoms, revealed a differential neural activation pattern compared to controls, but only during the enhance condition. Specifically, the mTBI group showed greater activation in the precentral gyrus, postcentral gyrus, inferior parietal lobe, insula, and superior temporal gyrus. Finally, the effect of PTSD symptoms during the enhance condition was associated with accentuated activation of the frontal and limbic regions implicated in both emotion regulation and PTSD. Hyperactivation of neural regions in the mTBI group during the enhance condition may reflect vigilance towards negative contextual stimuli and/or poor strategy that might result in suboptimal allocation of resources to regulate emotions.

Spoilers Affect the Enjoyment of Television Episodes but Not Short Stories.

While spoilers are culturally regarded as something that detracts enjoyment from a narrative, research has presented a complicated picture. When Leavitt and Christenfeld presented participants plot-crucial information to individuals before reading a short story, the story was subsequently enjoyed as much as, or more than, unspoiled stories. Other research shows that these findings may be driven by an interaction of individual differences, such as need for cognition, rather than a broad spoiling effect. In Experiment 1, we tested if reported enjoyment of a narrative decreased even when participants were alerted to the presence of a plot spoiler, to extend previous findings for short stories while adding a condition informing participants beforehand that their short stories was being spoiled. Experiment 2 extended this methodology to full-length episodes of television. Our results were different from previously reported positive effects of spoilers and show that spoilers, under certain circumstances, have a negative effect on enjoyment for television but not short stories.

North American Football Fans Show Neurofunctional Differences in Response to Violence: Implications for Public Health and Policy.

While social and behavioral effects of violence in the media have been studied extensively, much less is known about how sports affect perceptions of violence. The current study examined neurofunctional differences between fans and non-fans of North American football (a contact sport) while viewing violent imagery. Participants viewed images of violence in both football and non-football settings while high-resolution functional magnetic resonance imaging (fMRI) data were acquired from their brains. Neurological activation was compared between these violence types and between groups. Fans of football show diminished activation in brain regions involved in pain perception and empathy such as the anterior cingulate cortex, fusiform gyrus, insula, and temporal pole when viewing violence in the context of football compared to more broadly violent images. Non-fans of football showed no such effect for the types of violent imagery and had higher activation levels than fans of football for the specified brain regions. These differences show that fans of football may perceive violence differently when it is in the context of football. These fan attitudes have potential policy implications for addressing the issue of concussions in North American football.

Anxiety sensitivity and attentional bias to threat interact to prospectively predict anxiety.

The purpose of the present study was to examine anxiety sensitivity, attentional bias to threat (ABT), and the aggregate influence of these constructs as prospective predictors of anxiety. Participants (N = 176) completed a baseline assessment session which included the completion of self-report measures of anxiety and anxiety sensitivity, as well as an eye-tracking task in which eye movements were recorded during the viewing of neutral and threat images. Measures of anxiety and anxiety sensitivity were completed again as part of an online questionnaire battery at a 1-year follow-up session. As predicted, baseline anxiety sensitivity and ABT predicted anxiety at 1-year follow-up even after accounting for baseline anxiety. However, these main effects were qualified by a significant interaction effect such that those high in anxiety sensitivity at baseline reported relatively higher anxiety at the 1-year follow-up, but only if they also exhibited higher levels of ABT at baseline. Results suggest that individuals with this combination of vulnerability factors (high levels of both anxiety sensitivity and ABT) may be at particularly high risk for developing anxiety and may benefit from preemptive efforts to reduce ABT.

Primacy and recency effects for taste.

Historically, much of what we know about human memory has been discovered in experiments using visual and verbal stimuli. In two experiments, participants demonstrated reliably high recognition for nonverbal liquids. In Experiment 1, participants showed high accuracy for recognizing tastes (bitter, salty, sour, sweet) over a 30-s delay in a recognition task, even when the probe stimulus was only a different concentration within the same taste. In Experiment 2, participants tasted three liquids and showed both primacy and recency effects in a serial-position recognition task with varying delay lengths (15, 30, 45, 60 s). Recognition for liquids at the end of a list was most evident with shorter delay lengths (i.e., recency). Recognition for liquids at the start of the list was most evident with longer delay lengths (i.e., primacy). These data show that not only is gustatory information stored and maintained in working memory, but that memory for these liquids follow a recency-to-primacy shift in recognition memory. (PsycINFO Database Record

Examining Microstructural White Matter in Active Duty Soldiers with a History of Mild Traumatic Brain Injury and Traumatic Stress.

BACKGROUND: There is a high comorbidity of posttraumatic stress (PTS) and mild traumatic brain injury (mTBI), with largely overlapping symptomatology, in military service members. OBJECTIVE: To examine white matter integrity associated with PTS and mTBI as assessed using diffusion tensor imaging (DTI). METHOD: Seventy-four active-duty U.S. soldiers with PTS (n = 16) and PTS with co-morbid history of mTBI (PTS/mTBI; n = 28) were compared to a military control group (n = 30). Participants received a battery of neurocognitive and clinical symptom measures. The number of abnormal DTI values was determined (>2 SDs from the mean of the control group) for fractional anisotropy (FA) and mean diffusivity (MD), and then compared between groups. In addition, mean DTI values from white matter tracts falling into three categories were compared between groups: (i) projection tracts: superior, middle, and inferior cerebellar peduncles, pontine crossing tract, and corticospinal tract; (ii) association tracts: superior longitudinal fasciculus; and (iii) commissure tracts: cingulum bundle (cingulum-cingulate gyrus and cingulum-hippocampus), and corpus callosum. RESULTS: The comorbid PTS/mTBI group had significantly greater traumatic stress, depression, anxiety, and post-concussive symptoms, and they performed worse on neurocognitive testing than those with PTS alone and controls. The groups differed greatly on several clinical variables, but contrary to what we hypothesized, they did not differ greatly on primary and exploratory analytic approaches of hetero-spatial whole brain DTI analyses. CONCLUSION: The findings suggest that psychological health conditions rather than pathoanatomical changes may be contributing to symptom presentation in this population.

A longitudinal examination of the role of attentional control in the relationship between posttraumatic stress and threat-related attentional bias: An eye-tracking study.

The purpose of the present study was to use eye-tracking technology to (a) show that attentional control can be used to reduce attentional bias to threat (ABT) among those with higher levels of posttraumatic stress (PTS) symptoms, (b) identify the specific attentional control (AC) processes (i.e., inhibition, shifting, working memory updating) that account for this effect, and (c) determine the short- (sympathetic nervous system reactivity) and long-term effects (PTS symptoms) of using attentional control in this manner. At Time 1 (T1), participants (N = 116 trauma exposed) completed self-report measures, an eye-tracking task assessing ABT, and behavioral measures assessing cognitive processes. A subsample (n = 49) completed an online follow-up assessment (T2). AC at T1 moderated the PTS-ABT relationship. Inhibitory ability appears to be driving this effect. Those with higher PTS symptoms and higher AC at T1, who spent less time attending to threat stimuli and had the lowest sympathetic response, had the highest levels of PTS symptoms at T2. Findings suggest that the habitual use of AC (especially inhibition) to shift attention from threat to neutral stimuli may alleviate distress in the short-term for those with higher PTS symptoms, but maintain, and perhaps exacerbate, PTS symptoms over longer periods.

Compromised hippocampus-striatum pathway as a potential imaging biomarker of mild-traumatic brain injury and posttraumatic stress disorder.

OBJECTIVES: Military service members risk acquiring posttraumatic stress disorder (PTSD) and mild-traumatic brain injury (mTBI), with high comorbidity. Owing to overlapping symptomatology in chronic mTBI or postconcussion syndrome (PCS) and PTSD, it is difficult to assess the etiology of a patient's condition without objective measures. Using resting-state functional MRI in a novel framework, we tested the hypothesis that their neural signatures are characterized by functionally hyperconnected brain regions which are less variable over time. Additionally, we predicted that such connectivities possessed the highest ability in predicting the diagnostic membership of a novel subject (top-predictors) in addition to being statistically significant. METHODS: U.S. Army Soldiers (N = 87) with PTSD and comorbid PCS + PTSD were recruited along with combat controls. Static and dynamic functional connectivities were evaluated. Group differences were obtained in accordance with our hypothesis. Machine learning classification (MLC) was employed to determine top predictors. RESULTS: From whole-brain connectivity, we identified the hippocampus-striatum connectivity to be significantly altered in accordance with our hypothesis. Diffusion tractography revealed compromised white-matter integrity between aforementioned regions only in the PCS + PTSD group, suggesting a structural etiology for the PCS + PTSD group rather than being an extreme subset of PTSD. Employing MLC, connectivities provided worst-case accuracy of 84% (9% more than psychological measures). Additionally, the hippocampus-striatum connectivities were found to be top predictors and thus a potential biomarker of PTSD/mTBI. CONCLUSIONS: PTSD/mTBI are associated with hippocampal-striatal hyperconnectivity from which it is difficult to disengage, leading to a habit-like response toward episodic traumatic memories, which fits well with behavioral manifestations of combat-related PTSD/mTBI. Hum Brain Mapp 38:2843-2864, 2017. © 2017 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Exploring the Neurocircuitry Underpinning Predictability of Threat in Soldiers with PTSD Compared to Deployment Exposed Controls.

BACKGROUND: Prior work examining emotional dysregulation observed in posttraumatic stress disorder (PTSD) has primarily been limited to fear-learning processes specific to anticipation, habituation, and extinction of threat. In contrast, the response to threat itself has not been systematically evaluated. OBJECTIVE: To explore potential disruption in fear conditioning neurocircuitry in service members with PTSD, specifically in response to predictable versus unpredictable threats. METHOD: In the current study, active-duty U.S. Army soldiers with (PTSD group; n = 38) and without PTSD (deployment-exposed controls; DEC; n = 40), participated in a fear-conditioning study in which threat predictability was manipulated by presenting an aversive unconditioned stimulus (UCS) that was either preceded by a conditioned stimulus (i.e., predictable) or UCS alone (i.e., unpredictable). Threat expectation, skin conductance response (SCR), and functional magnetic resonance imaging (fMRI) signal to predictable and unpredictable threats (i.e., UCS) were assessed. RESULTS: Both groups showed greater threat expectancy and diminished threat-elicited SCRs to predictable compared to unpredictable threat. Significant group differences were observed within the amygdala, hippocampus, insula, and superior and middle temporal gyri. Contrary to our predictions, the PTSD group showed a diminished threat-related response within each of these brain regions during predictable compared to unpredictable threat, whereas the DEC group showed increased activation. CONCLUSION: Although, the PTSD group showed greater threat-related diminution, hypersensitivity to unpredictable threat cannot be ruled out. Furthermore, pre-trauma, trait-like factors may have contributed to group differences in activation of the neurocircuitry underpinning fear conditioning.

Delayed match-to-sample in working memory: A BrainMap meta-analysis.

Working memory (WM), or the ability to temporarily store and manipulate information, is one of the most widely studied constructs in cognitive psychology. Since its inception, it has become one of the leading explanations for how humans are able to operate on a cognitive level. The current study probed the neural networks underlying one of the most commonly used tasks, delayed match-to-sample (DMTS), to study WM. An activation likelihood estimation (ALE) analysis of 42 functional neuroimaging studies (626 participants) was conducted to demonstrate neural network engagement during DMTS. Results demonstrated strong convergence in brain regions commonly associated with the working memory construct (i.e., dorsolateral prefrontal cortex, fusiform gyrus, and posterior parietal cortex). However, neural activation in two regions frequently attributed to WM were absent from this meta-analysis: the anterior cingulate and the rostral prefrontal cortex, suggesting that these regions may be more sensitive to task or stimuli characteristics. In a post-hoc analysis, we deconstructed the DMTS meta-analysis to examine nonverbal versus verbal stimuli, and found notable neurofunctional differences such that DMTS using nonverbal stimuli consistently engaged the right middle frontal gyrus (BA 6/46) and precuneus (BA 7) more so than verbal stimuli based DMTS. These results provide a foundation for future models of functional connectivity that may elucidate subtle differences in working memory attributable to pathological processes.

A negative stimulus movement effect in pigeons.

Rhesus monkeys and humans perform more accurately in matching-to-sample tasks when the sample stimulus moves through space (Washburn et al., 1989; Washburn, 1993). This Stimulus Movement Effect (SME) is believed to be due to movement increasing attention toward the sample stimulus, creating an easier discrimination between the sample and choice stimuli. To date, there is no evidence for this phenomenon in a non-mammalian species. In the current study, we investigate the possibility of an SME in an avian species. Across three experiments, pigeons were tested with moving and stationary sample stimuli in a non-matching- to-sample task. The area and velocity by which the sample stimulus traveled was manipulated but no advantage for moving over stationary sample trials was found within or across sessions. Even when a delay condition was implemented, there was no advantage for moving sample trials. Contrary to the results found in humans and monkeys, pigeons performed better when the sample was stationary, a negative SME, and no evidence was found that stimulus movement increases discrimination performance.

Demonstration and validation of a new pressure-based MRI-safe pain tolerance device.

BACKGROUND: One of the barriers to studying the behavioral and emotional effects of pain using functional Magnetic Resonance Imaging (fMRI) is the absence of a commercially available, MRI-compatible, pressure-based algometer to elicit pain. The present study sought to address this barrier through creation and validation of a novel MRI-safe apparatus capable of delivering incremental, measurable amounts of pressure inside a scanning bore. NEW METHOD: We introduced an MR-safe device used to administer pressure-based pain. To test against a commercially available, MRI-incompatible algometer (AlgoMed), 199 participants reported their pain tolerance for both devices. A second experiment tested the validity of pressure-based pain in an MRI environment by comparing brain activation with established neural networks for pain. 10 participants performed an identical procedure to test for pain tolerance while being scanned in a 7T MRI scanner. RESULTS: Results support the validity and reliability of our novel device. In Study 1, pain tolerance with this device was strongly correlated with pain tolerance as measured by a commercially available algometer (r=0.78). In Study 2, this device yielded BOLD activation within the insula (BA 13) and anterior cingulate gyrus (BA 24); as pressure increased, activation in these areas parametrically increased. COMPARISON WITH EXISTING METHOD: These findings correspond to other studies using thermal, electrical, or mechanical pain applications. Behavioral and functional data demonstrate that this new device is a valid method of administering pressure-related pain in MRI environments. CONCLUSIONS: Our novel MRI-safe device is a valid instrument to measure and administer pressure-based pain.

The oddity preference effect and the concept of difference in pigeons.

Previous work in discrimination learning has shown that nonmatching (oddity) tasks are learned faster and more accurately than comparable matching tasks. This learning advantage has been coined the oddity preference effect (Wright & Delius in Journal of Experimental Psychology: Animal Behavior Processes, 31, 425-432. doi: 10.1037/0097-7403.31.4.425 , 2005). Pigeons trained in a nonmatching task, following training in a same/different (S/D) task, learned the abstract concept of difference (Daniel et al., in Animal Cognition, 18(4), 831-837, 2015), but they did not show the expected faster acquisition or high levels of transfer from the oddity preference effect. In the present study, experimentally naïve pigeons were trained in an identical nonmatching task to examine whether they would show the oddity preference effect on abstract-concept learning. These experimentally naïve pigeons did show an oddity preference effect; their transfer to novel configurations was above chance with the initial (smallest) set size (3-item set) and was substantially more accurate than novel transfer in similar match-to-sample (MTS) or S/D tasks (Bodily et al., in Journal of Experimental Psychology: Animal Behavior Processes, 34, 178-184. doi: 10.1037/0097-7403.34.1.178 , 2008; Katz & Wright in Journal of Experimental Psychology: Animal Behavior Processes, 32, 80-86. doi: 10.1037/0097-7403.32.1.80 , 2006). As the number exemplars in the training set increased, transfer to novel configurations increased and reached equivalence to trained-stimulus performance with a 24-item set. Despite this transfer being equal to baseline performance with a 24-item set, subsequent transfers following training with larger set sizes declined before eventually rising again to baseline performance. This unusual set-size function (with inflection points at the 24- and 96-set sizes) suggests that these pigeons may have combined item-specific and relational learning strategies with differing emphasis as they acquired the abstract concept.

Temporal dynamics of task switching and abstract-concept learning in pigeons.

The current study examined whether pigeons could learn to use abstract concepts as the basis for conditionally switching behavior as a function of time. Using a mid-session reversal task, experienced pigeons were trained to switch from matching-to-sample (MTS) to non-matching-to-sample (NMTS) conditional discriminations within a session. One group had prior training with MTS, while the other had prior training with NMTS. Over training, stimulus set size was progressively doubled from 3 to 6 to 12 stimuli to promote abstract concept development. Prior experience had an effect on the initial learning at each of the set sizes but by the end of training there were no group differences, as both groups showed similar within-session linear matching functions. After acquiring the 12-item set, abstract-concept learning was tested by placing novel stimuli at the beginning and end of a test session. Prior matching and non-matching experience affected transfer behavior. The matching experienced group transferred to novel stimuli in both the matching and non-matching portion of the sessions using a matching rule. The non-matching experienced group transferred to novel stimuli in both portions of the session using a non-matching rule. The representations used as the basis for mid-session reversal of the conditional discrimination behaviors and subsequent transfer behavior appears to have different temporal sources. The implications for the flexibility and organization of complex behaviors are considered.