RESUMO
In the basic verbal task from Piaget, when a relation of the form if A > B and B > C is given, a logical inference A > C is expected. This process is called transitive inference (TI). The adapted version for animals involves the presentation of a simultaneous discrimination between stimuli pairs. In this way, when A+B-, B+C-, C+D-, D+E- is trained, a B>D preference is expected, assuming that if A>B>C>D>E, then B>D. This effect has been widely reported using several procedures and different species. In the current experiment TI was evaluated employing probabilistic reinforcement. Thus, for the positive stimuli a .7 probability was administered and for the negative stimuli a .3 probability was administered. Under this arrangement the relation A>B>C>D>E is still allowed, but TI becomes more difficult. Five pigeons (Columba Livia) were exposed to the mentioned arrangement. Only one pigeon reached the criterion in C+D- discrimination, whereas the remaining did not. Only the one who successfully solved C+D- was capable of learning TI, whereas the others were not. Additionally, it was found that correct response ratios did not predict BD performance. Consequently, probabilistic reinforcement disrupted TI, but some positional ordering was retained in the test. The results suggest that TI might be affected by associative strength but also by the positional ordering of the stimuli. The discussion addresses the two main accounts of TI: the associative account and the ordinal representation account.
RESUMO
The people of San Rafael Coxcatlán use Cordia curassavica to treat gastrointestinal and respiratory disorders. The aim of this work was to investigate the temporal variation of chemical composition and antimicrobial activity of the essential oil of C. curassavica in two seasons of the year (dry and rainy). The essential oil of aerial parts was obtained by steam distillation, 12 and 17 compounds were identified for dry and rainy seasons respectively by GC-MS. The major component was for the dry season 1,7,7-trimethyl tricyclo (2.2.1.0(2,6)) heptane (20.3 percent), and for the rainy season was germacrene (24.41 percent). The antibacterial activity of essential oils varies temporarily because was active in nine strains in the dry season and four in the wet. The more sensitive strains were Stapahylococcus epidermidis and Vibrio cholera. The essential oil obtained in dry season presented a MIC of 0.75 and 0.125 mg/mL, and for the rainy season a MIC of 1.00 and 0.375 mg/mL respectively. Rhizoctonia solani was the more sensitive fungi strain (IC25 0.1300 mg/mL) in the rainy season. These results show that the chemical composition and biological properties of essential oil of the C. curassavica have temporal variation.
La población de San Rafael para tratar padecimientos gastrointestinales y respiratorios emplean Cordia curassavica. El objetivo del presente trabajo fue investigar la variación temporal de la composición química y la actividad antimicrobiana del aceite esencial de C. curassavica colectada en dos épocas del año (sequía y lluvias). El aceite esencial se obtuvo mediante la técnica de arrastre de vapor y los componentes se identificaron por CG-MS. En la época de secas se detectaron 12 compuestos y 17 en la de lluvias. El principal componente para la época de secas fue el 1,7,7 trimetil triciclo (2.2.1.0(2,6)) heptano (20.3 por ciento) y para la temporada de lluvias fue el germacrano (24.41 por ciento). La actividad antibacteriana del aceite esencial varía temporalmente porque fue activo sobre nueve cepas en la época seca y sobre cuatro cepas en la época lluviosa. Las cepas más sensibles para ambas estaciones fueron Stapahylococcus epidermidis y Vibrio cholerae. En la época de seca, el aceite esencial presentó la concentración mínima inhibitoria (CMI) de 0.75 y 0.125mg/mL, mientras que en la época de lluvias fueron de 1.00 y 0.375 mg/mL respectivamente. La cepa fúngica más sensible fue Rhizoctonia solani (IC25 0.130 mg/mL) en la época de lluvia. Estos resultados muestran que la composición química y las propiedades biológicas de los aceites esenciales de Cordia curassavica varian de acuerdo a la época del año.