Alfaro, L. Cabrera, R.

Estudios previos de forrajeo colectivo sugieren que la estrategia de parasitar ocurre en una alta proporción porque podría conllevar a un menor desgaste energético; este desgaste ha sido evaluado considerando la distancia a la cual se ubican los sujetos respecto del centro del área de búsqueda. Este trabajo evaluó, en condiciones de laboratorio, la relación entre la adquisición de estrategias y la longitud de los recorridos realizados por ratas macho expuestas a una situación colectiva de búsqueda de alimento. Seis grupos fueron expuestos a diferentes tipos de alimento: semillas o pellets. Al contrastar los recorridos de los sujetos en función del tipo de alimento, se observó que los grupos expuestos a semillas hicieron recorridos más cortos. En la comparación de recorridos realizados por sujetos que emplean una estrategia diferente se apreciaron recorridos significativamente más cortos para los productores, lo cual podría implicar que los recorridos de los productores son más directos y eficientes para conseguir alimento. Una simplificación de la función de Newell & Rosenbloom (1981) fue utilizada para mostrar el estado estable de los recorridos (curva de aprendizaje).

A Functional Analysis of Behavior in the Balloon Analogue Task

balloon analogue, choice, functional Analysis, punishment, risk taking

Robles, E.

In the balloon analogue task, a continuous schedule of positive reinforcement and a random ratio schedule of punishment for “pump” responses operate simultaneously, along with the opportunity to terminate each trial and avoid an impending punishing stimulus. In this study, the functional properties of game points and point losses were analyzed in three groups of college students (N=92) by varying the density of balloon explosions throughout the 30-balloon session. The within-session changes in density of explosions produced immediate systematic adjustments in pump responses per balloon. The results showed that 1) the number of pumps per balloon is sensitive to the local probability of explosions; 2) the suppression brought on by explosions depends on the temporal distance to the last explosion and the number of consecutive explosions; 3) suppression appears to be non-linear, with stronger effects as the local probability of explosions increases; and, 4) within limits, points without assigned extrinsic value may serve as reinforcers in the balloon analogue environment for populations with a history of game playing. Given these findings, a valuable strategy for future research may be to study differential reactivity to wins and losses as a proximal determinant of total scores that is amenable to experimental analysis.

Comparing Models of Intertemporal Choice: Fitting Data from Lewis and Fischer 344 Rats

AIC weights, delay discounting models, Fischer 344, Lewis, rats

Aparicio, C.F.

Formal comparisons of delay discounting models have been conducted using data from humans, with only one study comparing delay discounting data by controls and pathological gamblers. This is the first study using data from nonhuman animals to compare models of intertemporal choice. For each model fitting the impulsive choices of Lewis (LEW) and Fischer (F344) rats, the Akaike’s (1973) information criterion (AIC) and its corresponding AIC weight were computed. The main goal was to show that AIC weights are easy to compute and simplify the interpretation of results generated by single-parameter and dual-parameter models of intertemporal choice. Segments of a published data set (Aparicio, Elcoro, & Alonso-Alvarez, 2015) were used to compare five models of intertemporal choice. All models nicely fitted the data of the LEWs and F344s at the group and individual levels of analysis. Formal comparisons based on AIC weights, evidence ratios of Aikaike weights, and normalized probabilities revealed that Mazur’s (1987) hyperbolic-decay model is the best and most parsimonious model fitting the group and individual data from LEWs and F344s, followed by Samuelson’s (1937) exponential discounted utility function.

Analysis of sequential patterns of stereotypy and variability in human conditional discrimination tasks

heterogeneous, homogeneous, humans, matching-to-sample, sequential patterns, stereotypy, variability

In order to evaluate whether reinforce responses of repetition or varied did produce sequential patterns in humans, the frequency distributions of the sequences performed under a conditional discrimination paradigm were analyzed. To make such analysis, data were taken from a previous study in which children and undergraduate students were exposed to tasks of repetition or variability using a matching-to-sample procedure. On the stereotypy task the same choice made in the previous trial was reinforced, while in the variability task a response was considered correct when was distinct from the choice made in the previous trial. Those authors reported that the children and undergraduates in their study obtained the maximum number of correct responses on stereotypy tasks, while on the variability tasks the number of correct responses was lower and the maximum number of correct responses was rarely reached. Another finding was that sequential effects by the order of the tasks were identified, such that when stereotypy was preceded by variability performance was not optimal, though when the order of the tasks was reversed, the opposite result was found. However, one aspect omitted in that study was analyzing possible sequences of responses on both tasks. Once performed that analysis revealed two sequence patterns: a) in the stereotypy condition one pattern showed persistence to respond to one specific sequence; and, b) in the variability condition, the frequency of sequences was distributed uniformly among the six variable sequences options. We discuss whether the matching-to-sample procedure, in addition to producing stereotypy, is useful for producing varied responses or simply generates an alternation of responses that switch from one option to another.