Spatial Discounting of Food and Social Rewards in Guppies (Poecilia Reticulata)

Abstract

In temporal discounting, animals trade off the time to obtain a reward against the quality of a reward, choosing between a smaller reward available sooner versus a larger reward available later. Similar discounting can apply over space, when animals choose between smaller and closer versus larger and more distant rewards. Most studies of temporal and spatial discounting in non-human animals use food as the reward, and it is not established whether animals trade off other preferred stimuli in similar ways. Here, we offered female guppies (Poecilia reticulata) a spatial discounting task in which we measured preferences for a larger reward as the distance to it increased relative to a closer but smaller reward. We tested whether the fish discounted reward types differently by offering subjects either food items or same-sex conspecifics as rewards. Before beginning the discounting tasks, we conducted validation tests to ensure that subjects equally valued the food and social stimuli in the quantities provided. In the discounting task, subjects switched their preferences from the larger to the smaller reward as the distance to the larger reward increased (spatial discounting), but the pattern and magnitude of discounting did not differ across the two reward types. These findings indicate that guppies show similar patterns of discounting for food and social rewards in a spatial task. In an examination of travel times, however, the fish swam faster to food rewards than to shoaling partners. Analysis of travel times suggests that fish temporally discounted social rewards less steeply than food rewards. Thus, reward type influences temporal discounting, suggesting a dissociation between temporal and spatial discounting. Our results illustrate how animals adjust choices and travel times depending on both the type of cost (time, distance) and benefits (food, social partners).

Intertemporal choice in lemurs

“…Historically, most experimental studies of intertemporal choices in animals tested primarily pigeons and rats (McDiarmid and Rilling, 1965;Richards et al, 1997). More recently, however, researchers have tested many more species, including insects, fish, birds, mice, and primates (Bateson and Kacelnik, 1996;Tobin et al, 1996;Brunner and Hen, 1997;Cheng et al, 2002;Stevens et al, 2005a;Rosati et al, 2007;Pearson et al, 2010;Vick et al, 2010;Mühlhoff et al, 2011).…”

Translational research into intertemporal choice: The Western scrub-jay as an animal model for future-thinking

“…Dufour et al, 2012;Hillemann et al, 2014;Thom and Clayton, 2014), dogs (Leonardi et al, 2012), cockatoos (Auersperg et al, 2013), and fish (e.g. Mühlhoff et al, 2011). The methodologies used in these studies vary tremendously, but most can be described as either delay-choice tasks that ask subjects to point to their preferred reward (e.g.…”

“…Other tasks offer variations on these themes, like hybrid-delay tasks that ask subjects to make an initial choice and then give them the opportunity to renege while waiting (Paglieri et al, 2012;Beran et al, 2013), delayed exchange tasks in which the subject actually receives the immediate payoff at the onset of the delay and must return it at the end to get the larger/more valuable payoff (e.g. Dufour et al, 2012;Wascher et al, 2012), and delay-distance tasks that apply delay as the time taken to travel to a reinforcer in order to mimic foraging conditions (Mühlhoff et al, 2011;Stevens et al, 2005b).…”

Investigating intertemporal choice through experimental evolutionary robotics

“…To justify this choice, we made sure that movement would have no additional cost for the agent, aside from the time spent moving -either because the robot did not consume energy at all (Study 1), or because energy consumption depended solely on the passing of time, regardless of whether the robot was moving or not (Study 2). Besides, this choice is not completely arbitrary: many natural instances of intertemporal choice in animals involve a spatial component (e.g., patch exploitation in blue jays and foraging decisions in baboons; Stephens and Anderson, 2001;Noser and Byrne, 2007), and spatial decision making has been experimentally studied in relation to delay discounting in various species (e.g., guppies, marmosets, and cotton-top tamarins; Stevens et al, 2005b;Mühlhoff et al, 2011).…”