Reberlab Cognitive Neuroscience of Learning and Memory

Our most recent research.

Neuroscience Meets Cryptography: Designing Crypto Primitives Secure Against Rubber Hose Attacks

Bojinov, H., Sanchez, D., Reber, P., Boneh, D., & Lincoln, P.

Cryptographic systems often rely on the secrecy of cryptographic keys given to users. However, many schemes cannot resist coercion attacks where the user is forcibly asked by an attacker to reveal the key. These attacks, known as rubber hose cryptanalysis, are often the easiest way to defeat cryptography. We present a new approach to protecting against coercion attacks using the concept of implicit learning from cognitive psychology. Implicit learning refers to learning of patterns without any conscious knowledge of the learned pattern. We use a carefully crafted computer game to plant a secret password in the participant’s brain without the participant having any conscious knowledge of the trained password. While the planted secret can be used for authentication, the participant cannot be coerced into revealing it since he or she has no conscious knowledge of it. We performed a number of user studies using Amazon’s Mechanical Turk to verify that participants can successfully re-authenticate over time and that they are unable to reconstruct or even recognize short fragments of the planted secret.

Posted by Danny

The Effect of Ego Depletion on Implicit Skill Learning

Sanchez, D.J., Wesley, A.H., & Reber, P.J.

Although implicit skill learning occurs incidentally and without conscious awareness of what is learned, the rate and effectiveness of learning may still be affected by variation in the cognitive state of the learner during practice. Ego depletion theory states that humans possess a limited store of cognitive resources that, when depleted, results in deficits in self-regulation and cognitive control. While the specific mechanism of ego depletion is not known, its effects on processes associated with dopaminergic function suggest the possibility that ego depletion might affect the dopamine-gated plasticity that is hypothesized to support implicit sequential skill learning. In a first experiment this idea was tested using an assessment of pre-experimental depletion given prior to training on the Serial Interception Skill Learning (SISL) task and relative depletion state was found to predict implicit learning rate. In a second experiment, ego depletion was manipulated by having participants complete a depleting task prior to a standard implicit learning protocol. Depleted participants exhibited less learning than did non-depleted controls. In a third experiment, depletion was administered after training and was not found to interfere with skilled performance, suggesting the effect of ego depletion is specific to learning. These results indicate that in both training and educational contexts, ego depletion should be avoided prior to practice to maximize training gains even from rote or repetitive practice.

Submitted to CABN.

Posted by Danny

Explicit pre-training instruction does not improve implicit perceptual-motor sequence learning

Sanchez, D.J. & Reber, P.J.

Skills are typically learned by initial explicit instruction followed by repetitive practice to hone and improve performance. Memory systems theory provides a framework for characterizing the basis of this process whereby declarative memory plays a large initial role in instruction and implicit learning subsequently becomes important during practice. However, prior studies dissociating these two types of memory have not indicated how these systems interact during the skill learning process. The types of memory could operate largely independently, with explicit memory merely providing an initial scaffolding to guide future practice. Alternately, there could be cooperative interactions between the systems by which they form a shared representation that drives performance. Using an implicit perceptual-motor sequence learning task, skill learning was compared when explicit instruction was available or under typical incidental learning conditions. In Experiment 1, sequence pre-instruction did not lead to improved skill learning, but explicit memory for the sequence was poor after practice. In Experiment 2, improved instruction led to better explicit knowledge, but as in Experiment 1, sequence learning was robust and equivalent for both conditions. The lack of an instruction benefit suggests that during skill learning, implicit and explicit memory operate independently. Initial instruction appears to mainly serve to guide initial action sequence performance so that it can be made faster, more accurate and more fluid by implicit learning during repetitive practice.

Submitted to Memory & Cognition

Posted by Danny