Exploration of human search behaviour: a multidisciplinary perspective

The following work presents an exploration of human search behaviour both from biological and computational perspectives. Search behaviour is defined as the movements made by an organism while attempting to find a resource. This work describes some of the principal procedures used to record movement, methods for analysing the data and possible ways of interpreting the data. In order to obtain a database of searching behaviour, an experimental setup was built and tested to generate the search paths of human participants. The test arena occupied part of a football field and the targets consisted of an array of 20 golf balls. In the first set of experiments, a random and regular distribution of targets were tested. For each distribution, three distinct conspicuity levels were constructed: a cryptic level, in which targets were painted the same colour as the grass, a semi-conspicuous level in which targets were left white and a conspicuous condition in which the position of each target was marked by a red flag, protruding one metre from the ground. The subjects tested were 9-11 year old children and their search paths were collected using a GPS device. Subjects did not recognise the spatial cues regarding the way targets were spatially distributed. A minimal decision model, the bouncing search model, was built based on the characteristics of the childrens search paths. The model produced an outstanding fit of the children’s behavioural data. In the second set of experiments, a new group of children were tested for two new distributions obtained by arranging the targets in patches. Again, children appeared unable to recognise spatial information during the collection processes. The children’s behaviour once again produced a good match with that of the bouncing search model. This work introduces several new methodological aspects to be explored to further understand the decision processes involved when humans search. Also, it illustrates that integrating biology and computational science can result in innovative research

Spatial Distribution of Taenia solium Porcine Cysticercosis within a Rural Area of Mexico

Cysticercosis is caused by Taenia solium, a parasitic disease that affects humans and rurally bred pigs in developing countries. The cysticercus may localize in the central nervous system of the human, causing neurocysticercosis, the most severe and frequent form of the disease. There appears to be an association between the prevalence of porcine cysticercosis and domestic pigs that wander freely and have access to human feces. In order to assess whether the risk of cysticercosis infection is clustered or widely dispersed in a limited rural area, a spatial analysis of rural porcine cysticercosis was applied to 13 villages of the Sierra de Huautla in Central Mexico. Clustering of cases in specific households would indicate tapeworm carriers in the vicinity, whereas their dispersal would suggest that the ambulatory habits of both humans and pigs contribute to the spread of cysticercosis. A total of 562 pigs were included in this study (August–December 2003). A global positioning system was employed in order to plot the geographic distribution of both cysticercotic pigs and risk factors for infection within the villages. Prevalence of pig tongue cysticercosis varied significantly in sampled villages (p = 0.003), ranging from 0% to 33.3% and averaging 13.3%. Pigs were clustered in households, but no differences in the clustering of cysticercotic and healthy pigs were found. In contrast, the presence of pigs roaming freely and drinking stagnant water correlated significantly with porcine cysticercosis (p = 0.07), as did the absence of latrines (p = 0.0008). High prevalence of porcine cysticercosis proves that transmission is still quite common in rural Mexico. The lack of significant differentiation in the geographical clustering of healthy and cysticercotic pigs weakens the argument that focal factors (e.g., household location of putative tapeworm carriers) play an important role in increasing the risk of cysticercosis transmission in pigs. Instead, it would appear that other wide-ranging biological, physical, and cultural factors determine the geographic spread of the disease. Extensive geographic dispersal of the risk of cysticercosis makes it imperative that control measures be applied indiscriminately to all pigs and humans living in this endemic area

Validity and reliability of the kiddie schedule for affective disorders and schizophrenia present and lifetime version DSM-5 (K-SADS-PL-5) Spanish version

Background: There are various language adaptations of the Schedule for Affective Disorders and Schizophrenia for School Age Children Present and Lifetime Version (K-SADS-PL). In order to comply with the changes in DSM classification, the Spanish edition of the interview was in need of update and evaluation. Methods: K-SADS-PL was adapted to correspond to DSM-5 categories. All clinicians received training, and a 90% agreement was reached. Patients and their parents or guardians were interviewed and videotaped, and the videos were exchanged between raters. Factor analysis was performed and inter-rater reliability was calculated only in the case of diagnoses in which there were more than five patients. Results: A total of 74 subjects were included. The Factor Analysis yielded six factors (Depressive, Stress Hyperarousal, Disruptive Behavioral, Irritable Explosive, Obsessive Repetitive and Encopresis), representing 72% of the variance. Kappa values for inter-rater agreement were larger than 0.7 for over half of the disorders. Conclusions: The factor structure of diagnoses, made with the instrument was found to correspond to the DSM-5 disorder organization. The instrument showed good construct validity and inter-rater reliability, which makes it a useful tool for clinical research studies in children and adolescents

Cognitive impairment and its improvement after six months in adolescents with schizophrenia

Studies evaluating the cognitive impairment in schizophrenic adolescents reported a variable course following antipsychotic treatment, with improvement being associated to patients' demographic or clinical characteristics. Objectives: To examine the cognitive impairments of a Mexican sample of adolescents with schizophrenia using the MATRICS Consensus Cognitive Battery (MCCB) before and after six months of antipsychotic treatment and to determine which demographic or clinical characteristics could be associated to cognitive improvement. Methods: A sample of 87 Mexican patients was evaluated with the MCCB. Domain scores for three age groups (12–13, 14–15 and 16–17 y.o.) were obtained at baseline, and after 3 and 6 months of treatment. The groups were compared for demographic and clinical variables (sex, school attendance, years of education, being on their first psychotic episode, duration of illness and mean dose of antipsychotic), and a logistic regression analysis was performed to determine which variables predicted larger improvement. Results: The baseline performance showed scores below the standardized mean, with improvement in all domains except for social cognition; female adolescents showed a larger improvement in attention/vigilance and visual learning domains. Conclusions: We observed cognitive impairments on schizophrenic adolescents, which improved after six months of treatment in almost all domains. Keywords: Cognitive dysfunction, Follow-up studies, Psychotic disorders, Attention, Latin American, MATRIC

Human Foragers: Searchers by Nature and Experience

Diverse studies of human foraging have revealed behavioral strategies that may have evolved as adaptations for foraging. Here, we used an outdoor experimental search task to explore the effect of three sources of information on participants’ performance: (i) information obtained directly from performing a search, (ii) information obtained prior to testing in the form of a distilled snippet of knowledge intended to experimentally simulate information acquired culturally about the environment, and (iii) information obtained from experience of foraging for natural resources for economic gain. We found that (i) immediate searching experience improved performance from the beginning to the end of the short, 2-min task, (ii) information priming improved performance notably from the very beginning of the task, and (iii) natural resource foraging experience improved performance to a lesser extent. Our results highlight the role of culturally transmitted information as well as the presence of mechanisms to rapidly integrate and implement new information into searching choices, which ultimately influence performance in a foraging task

The Tower Building Task: A Behavioral Tool to Evaluate Recreational Risk-Taking

Risk-taking is a fundamental aspect of life spanning diverse contexts. Despite many tests being readily available, the behavioral assessment of risk propensity in recreational contexts, where decisions are not necessarily motivated by monetary gains or losses, is not well represented. As the tower building task (TBT) shares features of recreational activities, we evaluated whether it could assess risk-taking in this type of scenario. In the TBT, participants use standard-size wooden blocks to build the tallest tower they can within a 10 min period. In the current study we (i) examined methodological modifications to the task to either promote or reduce risky behavior and (ii) tested possible associations between the TBT scores and those of two commonly used risk-taking evaluations: The Balloon Analogue Risk Task (BART) and the Sensation Seeking Scale (SSS). We found that limiting the number of permitted collapses decreased the willingness to take risks, whereas challenging participants to exceed a “record” height increased risk-taking. TBT scores of one of the conditions correlated with scores of the BART and the SSS, particularly with the subscale addressing recreational activities. These findings suggest that the TBT offers a potentially useful means of evaluating risk-taking behaviors akin to those of the recreational domain

Meta-analysis to implement alpha-synuclein in extracellular vesicles as a potential biomarker for parkinson’s disease

Background: In Parkinson’s disease (PD), exosomes carry α-synuclein (α-syn), a fibrillar protein aggregates with potential value as a biomarker. Objective: Evidence on blood levels of exosomal α-syn in PD patients and controls was reviewed for their consistency. Methods: Thirty-six studies on exosomal α-syn concentrations in PD were identified in a systematic literature search and meta-analysis. Results: Both raw and ratio-adjusted blood exosomal α-syn levels were consistently higher in PD patients than in controls. The standardized mean difference (SMD) was 1.54 (0.18-2.90, CI95%, p < 0.01) and 1.53 (0.23-2.83, CI95%, p < 0.01), respectively. Conclusion: Our results suggest that exosomal α-syn concentrations could be a useful biomarker for PD

Evidence of long-term allocentric spatial memory in the Terrestrial Hermit Crab Coenobita compressus.

Spatial learning is a complex cognitive skill and ecologically important trait scarcely studied in crustaceans. We investigated the ability of the Pacific (Ecuadorian) hermit crab Coenobita compressus, to learn an allocentric spatial task using a palatable novel food as reward. Crabs were trained to locate the reward in a single session of eleven consecutive trials and tested subsequently, for short- (5 min) and long-term memory 1, 3 and 7 days later. Our results indicate that crabs were able to learn the location of the reward as they showed a reduction in the time required to find the food whenever it was present, suggesting a visuo-spatial and olfactory cue-guided task resolution. Moreover, crabs also remember the location of the reward up to 7 days after training using spatial cues only (without the food), as evidenced by the longer investigation time they spent in the learned food location than in any other part of the experimental arena, suggesting a visuo-spatial memory formation. This study represents the first description of allocentric spatial long-term memory in a terrestrial hermit crab