Mikaël Molet

Decision making by humans in a behavioral task: Do humans, like pigeons, show suboptimal choice?

Consistent with human gambling behavior but contrary to optimal foraging theory, pigeons show a strong preference for an alternative with low probability and high payoff (a gambling-like alternative) over an alternative with a greater net payoff (Zentall & Stagner, Proceedings of the Royal Society B, 278, 1203-1208, 2011). In the present research, we asked whether humans would show suboptimal choice on a task involving choices with probabilities similar to those for pigeons. In Experiment 1, when we selected participants on the basis of their self-reported gambling activities, we found a significantly greater choice of the alternative involving low probability and high payoff (gambling-like alternative) than for a group that reported an absence of gambling activity. In Experiment 2, we found that when the inhibiting abilities of typical humans were impaired by a self-regulatory depletion manipulation, they were more likely to choose the gambling-like alternative. Taken together, the results suggest that this task is suitable for the comparative study of suboptimal decision-making behavior and the mechanisms that underlie it.

Simultaneous discrimination reversal learning in pigeons and humans: anticipatory and perseverative errors

Pigeons were trained on a two-choice simultaneous discrimination (red vs. green) that reversed midway through each session. After considerable training, they consistently made both anticipatory errors prior to the reversal and perseverative errors after the reversal, suggesting that time (or number of trials) into the session served as a cue for reversal. In Experiment 2, to discourage the use of time as a cue, we varied the location of the reversal point within the session such that it occurred semirandomly after Trial 10, 25, 40, 55, or 70. Pigeons still tended both to anticipate and to perseverate. In Experiment 3, we required 20 pecks to a stimulus on each trial to facilitate memory for the preceding response and sensitivity to local reinforcement contingencies, but the results were similar to those of Experiment 2. We then tested humans on a similar task with a constant (Experiment 4) or variable (Experiment 5) reversal location. When the reversal occurred consistently at the midpoint of the session, humans, like pigeons, showed a tendency to anticipate the reversal; however, they did not show perseverative errors. When the reversal location varied between sessions, unlike pigeons, humans adopted a win–stay/lose–shift strategy, making only a single error on the first trial of the reversal.

A focused attention intervention for coping with ostracism

Ostracism-being excluded and ignored-thwarts satisfaction of four fundamental needs: belonging, self-esteem, control, and meaningful existence. The current study investigated whether training participants to focus their attention on the here-and-now (i.e., focused attention) reduces distress from an ostracism experience. Participants were first trained in either focused or unfocused attention, and then played Cyberball, an online ball-tossing game for which half the participants were included or ostracized. Participants reported their levels of need satisfaction during the game, and after a short delay. Whereas both training groups experienced the same degree of need-threat in the immediate measure, participants who were trained in focused attention showed more recovery for the delayed measure. We reason that focused attention would not reduce the distress during the ostracism experience, but it aided in recovery by preventing participants from reliving the ostracism experience after it concludes.

Timing: an attribute of associative learning.

The evidence reviewed in this paper suggests that when two events occur in spatiotemporal proximity to one another, an association between the two events is formed which encodes the timing of the events in relation to one another (including duration, order, and interval). The primary evidence supporting the view that temporal relationships are encoded is that subsequent presentation of one event ordinarily elicits behavior indicative of an expectation of the other event at a specific time. Thus, temporal relationships appear to be one of several attributes encoded at acquisition.

Integration of spatial relationships and temporal relationships in humans

Three experiments tested human participants on a two-dimensional, computer, landmark-based search task to assess the integration of independently acquired spatial and temporal relationships. Experiment 1 showed that A-B spatial training followed by B-outcome spatial training resulted in spatial integration in such a way that A was effectively associated with the outcome. Experiment 2 showed that A-B spatial and temporal training followed by B-outcome spatial and temporal training resulted in integration that created both spatial and temporal relationships between A and the outcome. Experiment 3 refuted an alternative explanation, one that is based on decision-making speed, to the temporal-integration strategy that was suggested by Experiment 2. These results replicate in humans the observations regarding spatial integration made by Sawa, Leising, and Blaisdell (2005) using a spatial-search task with pigeons, and they extend those observations to temporal integration.

Acquisition, extinction and temporal discrimination in human conditioned avoidance.

Two experiments were conducted with the aim of designing a videogame for the study of human conditioned avoidance. Participants had to destroy enemy spaceships with the goal of increasing the score in a counter. Coloured signals might announce the launching of a bomb that could hit participants spaceship producing a 30 points decrease in participants score. Three groups of participants were trained in discriminating between a warning signal (W) and a safety signal (S) in Experiment 1. Instrumental group could avoid the loss of points by hiding the spaceship before the offset of W. Participants in the Yoked group received the same treatment received by their instrumental partners, regardless of their behaviour. In the Pavlovian group, W was always followed by the loss of points, regardless of participants behaviour. Discrimination between W and S was better in the Instrumental groups than in the Yoked and Pavlovian control groups. Experiment 2 found extinction of avoidance when the warning signal was not followed by the bomb. Temporal discrimination was found within the participants that received the instrumental contingency in both experiments, with higher avoidance response towards the end of the warning signal. Temporal discrimination disappeared after extinction in Experiment 2.

Conditioned Place Preference and Aversion for Music in a Virtual Reality Environment

The use of a virtual reality environment (VRE) enables behavioral scientists to create different spatial contexts in which human participants behave freely, while still confined to the laboratory. In this article, VRE was used to study conditioned place preference (CPP) and aversion (CPA). In Experiment 1, half of the participants were asked to visit a house for 2 min with consonant music and then they were asked to visit an alternate house with static noise for 2 min, whereas the remaining participants did the visits in reverse order. In Experiment 2, we used the same design as Experiment 1, except for replacing consonant music with dissonant music. After conditioning in both experiments, the participants were given a choice between spending time in the two houses. In Experiment 1, participants spent more time in the house associated with the consonant music, thus showing a CPP toward that house. In Experiment 2, participants spent less time in the house associated with the dissonant music, thus showing a CPA for that house. These results support VRE as a tool to extend research on CPP/CPA in humans.

When does integration of independently acquired temporal relationships take place

Prior research has found that when subjects independently acquire 2 associations with a common element (e.g., S1-S2 and S2-US), each with its own temporal relationship, they behave as if the 2 unique cues (i.e., S1 and US) have a known temporal relationship despite their never having been paired. This is interpreted as indicative of temporal integration of the memories acquired during Phase 1 and Phase 2 of training based on the element common to both experiences (i.e., S2). There are 2 times at which such integration of independent temporal relationships could plausibly occur: at the time of acquisition of the second relationship or at the time of testing. Three lick-suppression experiments with rats were performed to determine when integration occurs. This question of the moment of temporal integration was assessed by extinguishing the mediating element (S2) between learning of the second temporal relationship and testing of S1. Experiment 1 (using sensory preconditioning) and Experiment 2 (using second-order conditioning) found that this manipulation interfered with behavioral control by S1, suggesting that temporal integration occurred at the time of testing. Experiment 3 used spontaneous recovery, a hallmark phenomenon of extinction, to confirm that the S2-alone presentations in Experiments 1 and 2 attenuated integration as a result of extinction of S2. Implications for the temporal coding hypothesis (e.g., Savastano & Miller, 1998) are discussed.

Relative judgments affect assessments of stimulus duration

Humans were trained on two independent temporal discriminations, with correct choice dependent on the initial stimulus duration. In Experiment 1, the durations were 1.0 and 4.0 sec, with one set of choice stimuli, and 2.0 and 8.0 sec, with a different set of choice stimuli. The 2.0- and 4.0-sec values were selected to be the geometric mean of the two values in the other discrimination. In Experiment 2, the durations were 2.0 and 5.0 sec for one discrimination and 3.5 and 6.5 sec for the other. The 3.5- and 5.0-sec values were selected to be the arithmetic mean of the two values in the other discrimination. In both experiments, participants showed evidence for relational coding of the duration pairs. That is, the test durations were selected to be at the presumed bisection point (i.e., they should have produced indifferent choice), but instead the shorter test duration from the longer duration pair produced a “short” bias (in both experiments), whereas the longer duration from the shorter duration pair produced a “long” bias (in the second experiment). Results were similar to those from Zentall, Weaver, and Clement (2004) with pigeons.

Reaction time as a measure of human associative learning.

Studies of human associative learning have often used causal/predictive learning preparations in which participants decide whether or not a first event is effective in causing or predicting a second event (i.e., an outcome). Those preparations have proved successful in replicating many Pavlovian phenomena. In the present paper we tested a novel associative learning preparation in which visually presented letters were paired with a visual outcome. Reaction times (RTs) were recorded to assess associative strength between specific cues and the outcome. Combining two different dependent variables (RTs and type of response given), we propose a rule for evaluating the associative strength between two events. The preparation and the data transformation rule were successful in producing several Pavlovian phenomena including excitatory acquisition, extinction, overshadowing, and latent inhibition, as well as established summation effects. Advantages and limitations of this new preparation based on the use of RT are discussed.