Quantifying the effects of the differential outcomes procedure in humans: A systematic review and a meta‐analysis

The role of the differential outcomes procedure and schizotypy in the recognition of dynamic facial expressions of emotions

Emotional facial expression recognition is a key ability for adequate social functioning. The current study aims to test if the differential outcomes procedure (DOP) may improve the recognition of dynamic facial expressions of emotions and to further explore whether schizotypal personality traits may have any effect on performance. 183 undergraduate students completed a task where a face morphed from a neutral expression to one of the six basic emotions at full intensity over 10 s. Participants had to press spacebar as soon as they identified the emotion and choose which had appeared. In the first block, participants received no outcomes. In the second block, a group received specific outcomes associated to each emotion (DOP group), while another group received non-differential outcomes after correctly responding (NOP group). Employing generalized linear models (GLMs) and Bayesian inference we estimated different parameters to answer our research goals. Schizotypal personality traits did not seem to affect dynamic emotional facial expression recognition. Participants of the DOP group were less likely to respond incorrectly to faces showing Fear and Surprise at fewer intensity levels. This may suggest that the DOP could lead to better identification of the main features that differentiate each facial expression of emotion.

Attack rate, case fatality rate and determinants of measles infection during a measles outbreak in Ethiopia: systematic review and meta-analysis

BACKGROUND

Although Ethiopia is working towards measles elimination, a recurrent measles outbreak has occurred. To take appropriate measures, previously, many fragmented and inconsistent outbreak investigations were done, but there is no consolidated evidence on attack rate, case fatality rate, and determinants of measles infection during the measles outbreak. This systematic review and meta-analysis aimed to identify cumulative evidence on attack rate, case fatality rate, and determinants of measles infection during the outbreak.

METHODS

A systematic literature review and Meta-analysis was used. We searched Google Scholar, Medline/PubMed, Cochrane/Wiley Library, EMBASE, Science Direct, and African Journals Online databases using different terms. Investigations that applied any study design, data collection- and analysis methods related to the measles outbreak investigation were included. Data were extracted in an Excel spreadsheet and imported into STATA version 17 software for meta-analysis. The I2 statistics were used to test heterogeneity, and 'Begg's and 'Egger's tests were used to assess publication bias. The odds ratio (OR) with a 95% confidence interval (CI) was presented using forest plots.

RESULTS

Eight measles outbreak investigations with 3004 measles cases and 33 deaths were included in this study. The pooled attack rate (A.R.) and case fatality rate were 34.51/10,000 [95% CI; 21.33-47.70/10,000] population and 2.21% [95% CI; 0.07-2.08%], respectively. Subgroup analysis revealed the highest attack rate of outbreaks in the Oromia region (63.05 per 10,000 population) and the lowest in the Amhara region (17.77 per 10,000 population). Associated factors with the measles outbreak were being unvaccinated (OR = 5.96; 95% CI: 3.28-10.82) and contact history (OR = 3.90; 95% CI: 2.47-6.15).

CONCLUSION

Our analysis revealed compelling evidence within the outbreak descriptions, highlighting elevated attack and case fatality rates. Measles infection was notably linked to being unvaccinated and having a contact history. Strengthening routine vaccination practices and enhancing contact tracing measures are vital strategies moving forward.

Functional equivalence classes in rats: Repeated olfactory discrimination reversals and delayed stimulus probes

The simultaneous matching-to-sample procedures that are widely used to study stimulus equivalence in human participants have generally been unsuccessful in animals. However, functional equivalence classes have been demonstrated in pigeons and sea lions using a concurrent repeated reversal discrimination procedure. In this procedure, responding to one set of stimuli is reinforced but responding to a different set is not and the set associated with reinforcement is changed with multiple reversals during the experiment. The experiments reported here were designed to assess whether functional equivalence classes could be demonstrated in rats using similar techniques. Rats were initially trained with two sets of olfactory stimuli (six odors/set). Following many reversals, probe reversal sessions were conducted in which rats were exposed to a subset of the members of each set and, later in the session, the withheld stimuli were introduced. Responding to these delayed probe trials in accord with the reversed contingencies constituted transfer of function. There was some evidence of transfer in Experiment 1, but the effects were relatively weak and variable. Experiment 2 introduced procedural changes and found strong evidence of transfer of function consistent with the formation of functional equivalence classes. These procedures offer a promising strategy to study symbolic behavior in rodents.

Vicarious value learning by differential outcomes training: A social transfer of control methodology

This article adapts an existing experimental protocol for assessing individuals’ ability to transfer knowledge across instrumental and pavlovian learning stages. The protocol (Transfer of Control using differential outcomes learning) is adapted to fit social contexts wherein the pavlovian learning phase is modulated so that individuals are able to observe, and potentially learn from, the stimulus associated with reinforcing outcomes presented to another (observable) individual. Transfer of Control concerns participants combining knowledge of learned instrumental and pavlovian (stimulus, response, outcome) associations in order to ground the learning of new associations. The article describes the theoretical and procedural underpinnings of a novel Social Transfer of Control methodology. The use of such a methodology is two-fold: i) to serve as a guide to researchers interested in evaluating how individuals can learn from others in a partially observable setting, i.e. when behavioural and reinforcing outcome information is hidden, and bring to bear this knowledge on their own instrumental decision making; ii), to facilitate investigation of the routes of cognitive and emotional empathy, with potential applications for educational and clinical settings.•

Three stage Transfer of Control behavioural methodology is adapted to include a social (pavlovian) learning stage.

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Hypotheses can be tested that concern learning rewarding instrumental responses achieved by observation of others’ emotionally expressive reactions to differentially rewarding outcomes.

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Methodological and validation considerations for evaluating the above are presented

A social differential outcomes learning task: Performance, EEG, and questionnaire data

This article contains performance data, questionnaire ratings, and EEG data from a differential outcomes learning task from two experiments. In both experiments, the standard differential outcomes learning task was extended to involve a social dimension, in order to capture how people can learn from others by observation. In Experiment 1 (N = 20), using a within-subjects design, participants learned pairings of image stimuli in four conditions: 1) individual-differential outcomes, 2) individual-non-differential outcomes, 3) social-differential outcomes, and 4) social-non-differential outcomes. The social condition had a screen-captured video recording of the outcomes (but not the actions themselves) of another person performing the task. During the task, the performance of the participants was measured. After the task, participants rated their experience in a questionnaire. The procedure for Experiment 2 (N = 33) was similar to Experiment 1, but with a stronger social manipulation using a video of another person's face showing facial expressions reflecting the outcomes. In addition, EEG was measured while performing the task. For more insight, please see Vicarious value learning: Knowledge transfer through affective processing on a social differential outcomes task (Rittmo et al., 2020).

Implicit outcomes expectancies shape memory process: Electrophysiological evidence

The simple manipulation of pairing specific outcomes with the sample stimuli strongly affects discriminative learning and memory processes. This procedure has been named the Differential Outcomes Procedure (DOP) and is usually compared to a control condition (the non-differential procedure, NOP) consisting in the random administration of the outcomes after each correct response. Recent research has revealed that the DOP effect arises even under unconscious conditions. In this study, we explored the temporal dynamics of short-term memory processes in both the DOP and the NOP in the absence of awareness of either the outcome (Experiment 1A) or the initial sample stimulus (Experiment 1B) through the evoked-related potentials technique. Results showed distinctive electrophysiological activation patterns in the DOP compared with the NOP at encoding, maintenance and retrieval phases. The present findings provide electrophysiological evidence of implicit-prospective processes involved in the DOP. They elucidate the processes that result in improved visual recognition memory.

Vicarious Value Learning: Knowledge transfer through affective processing on a social differential outcomes task

The findings of differential outcomes training procedures in controlled stimulus-response learning settings have been explained through theorizing two processes of response control. These processes concern: i) a stimulus-response route, and, ii) an outcome expectancy route through which valuations of stimuli (typically auditory or visual) may be represented. Critically, under certain contingencies of learning, the interaction of these two processes enables a transfer of knowledge. Transfer is hypothesized to occur via implicit inference for response selection given novel stimulus-response pairings. In this article, we test this transfer of knowledge, previously only examined in individual settings, in novel social settings. We find that participants are able to achieve transfer of knowledge and suggest they achieve this through vicariously learning the differential valuations of stimuli made by the (confederate) 'other' involved in the task. We test this effect under two experimental conditions through manipulation of the information made available to participants observing the confederate other's choices. The results of EEG recordings are, additionally, evaluated and discussed in the context of social signalling and emotional and cognitive empathy. We also consider implications for clinical and technological social learning settings.

Electrophysiological correlates of the differential outcomes effect in visual short-term memory

The differential outcomes procedure (DOP) consists in applying a specific outcome after each discriminative stimulus-correct response pairing, leading to improved performance in both memory and learning tasks (faster acquisition and/or higher response accuracy), compared to the non-differential outcomes procedure (NOP). The main aim of this study was to explore the electrophysiological correlates (ERPs) of the DOP in a visual short-term memory task, and to test whether a differential activation pattern would be observed depending on the outcomes condition (DOP vs. NOP). The ERP signals showed differences between both outcomes condition in all three phases of the short-term memory task: encoding, maintenance and retrieval. Our results are in accordance with the view that in the DOP condition the probe stimulus triggers a representation of the unique outcome, which remains active over the maintenance period (prospective process). In the NOP condition, in contrast, a representation of the probe stimulus is maintained (retrospective process). In addition, these results suggested that stimuli associated with unique outcomes captured attention involuntary at retrieval, decreasing the interference from distractor stimuli in the retrieval phase.

Discriminative learning and associative memory under the differential outcomes procedure is modulated by cognitive load

Working memory (WM) has been thought to be the cause of associative memory deficits in older adults. Previous research has demonstrated the benefits of a discriminative learning procedure, the differential outcomes procedure (DOP), to ameliorate such associative-memory maintenance deficits in situations that simulate adherence to medical prescriptions in both healthy and pathological ageing. Specifically, the DOP involves rewarding each correct response to each stimulus-stimulus association with a distinct and unique outcome (reinforcer). The aim of the present study was to explore the limits of this procedure by testing the amount of cognitive load at which the DOP improves discriminative learning and associative memory in a task that simulates adherence to medical treatment in undergraduate students. During the training phase, participants were asked to learn three pill/name (low-load condition) or four pill/name associations (high-load conditions) under the DOP in comparison with a control condition (the non-differential outcomes condition, NOP). Long-term retention of such learned associations was tested 1h and 1week after completion of the training phase. Participants showed a better accuracy and long-term retention of the learned associations when the DOP was used, but just in the high-load condition. These results suggest that when WM is overtaxed, the DOP plays a fundamental role in the long-term maintenance of the learned stimulus-stimulus associations, rendering such learning procedure as a useful technique to enhance people's discriminative learning and associative memory.

Enhanced learning and retention of medical information in Alzheimer's disease after differential outcomes training

BACKGROUND

Adherence to treatment is a crucial factor for patients who have chronic illnesses or multiple morbidities and polypharmacy, which is frequently found in older adults. The non-adherence to medications has important economic and social consequences as well as impacts on the health of the patients. One of the reasons that can explain the low adherence to treatment, is the memory deficits that are characteristics of this population and that are even more evident in cases that involve neurodegenerative diseases.

METHODS AND FINDINGS

In this study, we explore whether the differential outcomes procedure (DOP), which has been shown to be useful in improving discriminative learning and memory in different populations, may facilitate learning and retention of medical recommendations in older adults who have been diagnosed with Alzheimer's disease. The results demonstrate that when this procedure was applied, the patients showed improvements in learning and long-term retention of two pill/time of day associations in a situation that simulates adherence to medical prescriptions.

CONCLUSIONS

These findings contribute new data about the potential benefits of the DOP in patients with neurodegenerative disorders, highlighting the important role that this procedure could play in addressing important issues related to the health and quality of life of older adults, with or without neurodegenerative diseases, such as low adherence to medical treatments.