Mathijs Franssen

A free software package for a human online conditioned suppression preparation

Martians V2 is both a language syntax in which experiments can be written and an implementation of this syntax in a runtime application that, when fed a valid experiment text file, will execute the given experiment. It is based on the original Martians preparation, which has proven a valuable tool for assessing human online-conditioned suppression performance through research on a wide array of learning phenomena. This article can be read as a manual, both for using the Martians paradigm in general and for getting started with MartiansV2.

Acquisition and extinction of operant pain-related avoidance behavior using a 3 degrees-of-freedom robotic arm.

Abstract Ample empirical evidence endorses the role of associative learning in pain-related fear acquisition. Nevertheless, research typically focused on self-reported and psychophysiological measures of fear. Avoidance, which is overt behavior preventing the occurrence of an aversive (painful) stimulus, has been largely neglected so far. Therefore, we aimed to fill this gap and developed an operant conditioning procedure for pain-related avoidance behavior. Participants moved their arm to a target location using the HapticMaster (FCS Robotics; Moog Inc, East Aurora, New York), a 3 degrees-of-freedom, force-controlled robotic arm. Three movement trajectories led to the target location. If participants in the Experimental Group took the shortest/easiest trajectory, they always received a painful stimulus (T1 = 100% reinforcement; no resistance). If they deviated from this trajectory, the painful stimulus could be partly or totally prevented (T2 = 50% reinforcement; T3 = 0% reinforcement), but more effort was needed (T2 = moderate resistance and deviation; T3 = strongest resistance and largest deviation). The Yoked Group received the same reinforcement schedule irrespective of their own behavior. During the subsequent extinction phase, no painful stimuli were delivered. Self-reported pain-expectancy and pain-related fear were assessed, and avoidance behavior was operationalized as the maximal distance from the shortest trajectory. During acquisition, the Experimental Group reported more pain-related fear and pain-expectancy to T1 vs T2 vs T3 and deviated more from the shortest trajectory than the Yoked Group. During subsequent extinction, avoidance behavior, self-reported fear, and pain-expectancy decreased significantly, but conditioned differences persisted despite the absence of painful stimuli. To conclude, this operant learning task might provide a valid paradigm to study pain-related avoidance behavior in future studies.

Narrowing down the conditions for extinction of Pavlovian feature-positive discriminations in humans

The aim of this study was to delineate the minimal conditions for extinction of Pavlovian modulation in humans. Previous experiments at our lab showed that, after X ➔ A+/A– acquisition training, X– trials did not extinguish differential X ➔ A+/A– responding, while X ➔ A– trials did. Additionally, X ➔ A– extinction training seemed only to extinguish differential X ➔ A+/A– responding, while leaving differential responding on a concurrently trained Y ➔ B+/B– discrimination intact. It thus seemed that the X ➔ A+/A– discrimination can only be extinguished by X ➔ A– extinction trials. (Rescorla, Journal of Experimental Psychology: Animal Behavior Processes 12, 16–24, 1986), on the other hand, found that the minimal conditions for extinction were broader in pigeons: Namely, he found that an acquired X ➔ A+/A– discrimination could be extinguished by presenting the original feature X in combination with a different target (B) that was minimally trained as an exciter. We thus wanted to examine whether this was also the case in humans. We found that nonreinforced X ➔ B– presentations did not abolish discriminative X ➔ A/A responding when target B was a nonreinforced stimulus. Nonreinforced X ➔ B– trials did extinguish the X ➔ A+/A– discrimination when target B had previously been trained as a target for modulation (X ➔ B+/B– or Y ➔ B+/B– training) or as a reinforced exciter (B+). Our results thusf parallel and extend those in nonhuman animals (Rescorla, Journal of Experimental Psychology: Animal Behavior Processes 12, 16–24, 1986).

Reinstatement after human feature-positive discrimination learning

In two experiments, using an online conditioned suppression task, we investigated the possibility of reinstatement of extinguished feature-target compound presentations after sequential feature-positive discrimination training in humans. Furthermore, given a hierarchical account of Pavlovian modulation (e.g., Bonardi, 1998; Bonardi and Jennings, 2009), we predicted A-US reinstatement to be stronger than US-only reinstatement. In Experiment 1, participants learned a sequential feature-positive discrimination (X→A+|A-), which was subsequently extinguished (X→A-). During the following reinstatement phase, group US-only received US-only presentations (not signalled), group A-US received A-US presentations, and the Control group received exposure to the context, but no CSs or USs, for an equal amount of time. Reinstatement of differential X→A/A responding was observed in the US-only group but not in the Control or A-US groups. Although differential X→A/A responding was not significant in group A-US, responding to the X→A compound was significantly stronger compared to that in group US-only. Hence, it could be the case the group A-US showed stronger reinstatement, but that differential responding was abolished due to excitation gained by A. Experiment 2 was set up to circumvent the acquired excitation of A by testing transfer of the feature after A-US reinstatement to a different target, B. Participants acquired two discriminations, X→A/A and Y→B/B, of which X→A was then extinguished. Subsequently, group A-US received reinforced presentations of A during a reinstatement phase while group Control received exposure to the context. Final testing of the novel X→B compound was hypothesized to show higher responding in group A-US than in group Control, but findings of this approach were limited due to acquired equivalence and/or perceptual factors causing a secondary extinction effect. We conclude to have obtained clear evidence in favour of reinstatement of differential responding after human Feature-Positive discrimination training and subsequent compound extinction, but no evidence in favour of A-US presentations being a stronger trigger for reinstatement than are US-only presentations.