Interference in Dutch–French Bilinguals

In the present manuscript, we investigate the source of congruency effects in a group of Dutch–French bilinguals. In particular, participants performed a color-identification Stroop task, in which both (first language) Dutch and (second language) French distracting color words were presented in colors. The typical finding is impaired responding when the word and color are incongruent (e.g., “red” in blue) relative to congruent (e.g., “red” in red). This congruency effect is observed for both first and second language distracting color words. The current experiment used a 2-to-1 keypress mapping manipulation, which allows one to separate stimulus conflict (i.e., conflict between word and color meanings) and response conflict (i.e., conflict between potential responses). For both the first and second language, both stimulus and response conflict were observed. These results suggest that second language words influence semantic and response processing similarly to first language words, rather than having diminished semantic and/or response influences.

Cortical Spike Synchrony as a Measure of Input Familiarity

Spike synchrony, which occurs in various cortical areas in response to specific perception, action, and memory tasks, has sparked a long-standing debate on the nature of temporal organization in cortex. One prominent view is that this type of synchrony facilitates the binding or grouping of separate stimulus components. We argue instead for a more general function: a measure of the prior probability of incoming stimuli, implemented by long-range, horizontal, intracortical connections. We show that networks of this kind—pulse-coupled excitatory spiking networks in a noisy environment—can provide a sufficient substrate for stimulus-dependent spike synchrony. This allows for a quick (few spikes) estimate of the match between inputs and the input history as encoded in the network structure. Given the ubiquity of small, strongly excitatory subnetworks in cortex, we thus propose that many experimental observations of spike synchrony can be viewed as signs of input patterns that resemble long-term experience—that is, of patterns with high prior probability.

Effect of Frequency and Probability of Reward on Choice

In studies of probability and simultaneous discrimination learning choice is typically to the alternative with higher probability of reinforcement. However, in these situations probability of reinforcement is confounded with frequency of reinforcement, since the alternative with higher probability of reinforcement given a response also typically receives a greater absolute number of reinforcements in each session. In the present study pigeons were given separate stimulus training on two keys, with only one key presented on each trial, and numbers of trials and probabilities of reinforcement on each key manipulated to examine separately the effects of frequency of reinforcement and probability of reinforcement in different groups. Choice was examined on choice trials with both keys presented. When frequency and probability of reinforcement were manipulated independently, each of these variables affected choice.

Elicitation and Reinforcement as Separate Stimulus Functions

3 groups of 16 rats were trained to discriminate between two distinctive end boxes. Two groups discriminated between goal boxes while the third group discriminated between start boxes. These stimuli were then tested as secondary reinforcers in a T-maze. The groups trained to discriminate between goal boxes showed a statistically significant preference for the goal box previously associated with reinforcement. The third group showed no preference. It was concluded that discrimination training is not sufficient to establish an Sr without contiguity of stimulus and reward.