(Not) acquiring meaning in a second language: Are input deficits key?

Word meanings are not always parallel across languages, and second language (L2) learners often use words in non-native ways. Is the learning problem inherent in maintaining conflicting word-to-meaning mappings within an integrated lexical network, or is it due to insufficient attention to and input for acquiring L2 mappings? To help discriminate between these possibilities, we gave English speakers repeated exposures to 40 brief videos of actions, labeled with five novel words that cross-cut English labeling patterns. Half the participants were told only to learn the labels for the actions. The other half were told to figure out their meanings, which might differ from English. The Figure Out Meanings group made test choices faster and were also slightly more likely to produce definitions capturing the intended meanings. However, both groups performed well above chance in generalizing the novel words. High levels of choice performance for both groups point to insufficient input, rather than inherent properties of lexical networks, as the critical limiting factor in more typical L2 learning contexts. Speed and definition performance hint at some advantage to explicit attention in sorting out L1-L2 differences.

Chicken colour discrimination depends on background colour

ABSTRACTHow well can a bird discriminate between two red berries on a green background? The absolute threshold of colour discrimination is set by photoreceptor noise, but animals do not perform at this threshold; their performance can depend on additional factors. In humans and zebra finches, discrimination thresholds for colour stimuli depend on background colour, and thus the adaptive state of the visual system. We have tested how well chickens can discriminate shades of orange or green presented on orange or green backgrounds. Chickens discriminated slightly smaller colour differences between two stimuli presented on a similarly coloured background, compared with a background of very different colour. The slope of the psychometric function was steeper when stimulus and background colours were similar but shallower when they differed markedly, indicating that background colour affects the certainty with which the animals discriminate the colours. The effect we find for chickens is smaller than that shown for zebra finches. We modelled the response to stimuli using Bayesian and maximum likelihood estimation and implemented the psychometric function to estimate the effect size. We found that the result is independent of the psychophysical method used to evaluate the effect of experimental conditions on choice performance.

Identifying Feigned Cognitive Impairment: Investigating the Utility of Diffusion Model Analyses

Forced-choice performance validity tests are routinely used for the detection of feigned cognitive impairment. The drift diffusion model deconstructs performance into distinct cognitive processes using accuracy and response time measures. It thereby offers a unique approach for gaining insight into examinees’ speed-accuracy trade-offs and the cognitive processes that underlie their performance. The current study is the first to perform such analyses using a well-established forced-choice performance validity test. To achieve this aim, archival data of healthy participants, either simulating cognitive impairment in the Word Memory Test or performing it to the best of their ability, were analyzed using the EZ-diffusion model ( N = 198). The groups differed in the three model parameters, with drift rate emerging as the best predictor of group membership. These findings provide initial evidence for the usefulness of the drift diffusion model in clarifying the cognitive processes underlying feigned cognitive impairment and encourage further research.

Below Chance Performance of p < .05 or p < .20: Frequency of Statistically Below Chance Scores in Dementia

Objective A p-value of < .05 has traditionally been utilized to determine below chance performance on forced-choice performance validity tests (PVT). Recently, Binder and colleagues (2014 & 2018) proposed that the p-value cutoff increase to < .20. To ensure this does not result in frequent false-positive errors in patients who are likely to have significant cognitive impairment, frequency of below chance scores at both p-values were examined within the context of possible dementia. Method Archival data of cognitively impaired inpatient (n = 55; mean RBANS Total Score = 64.67) and outpatient (n = 203; mean RBANS Total Score = 74.15) older adults without external incentives were examined to determine frequency of below chance performances on the Coin-in-the-Hand Test. To supplement this data and examine below chance performance on a second PVT, the authors reviewed empirical literature and extracted data on TOMM performance in individuals with dementia. Four studies (n = 269 patients) provided data that could be extracted. Results No patient produced a Coin-in-the-Hand Test score (0/258 individuals) reaching either p value cutoff. Similarly, no patient produced a TOMM Trial 2 (0/121 individuals) or Retention score (0/84 individuals) reaching either p value cutoff. For TOMM Trial 1, no patient (0/44) scored at p < .05 but two patients (2/64) scored at p < .20. Conclusions No individual in this study produced scores on either PVT reaching the p < .05 cutoff. At the p < .20 cutoff, there were only 2 out of 527 performances (0.4%) that reached this threshold; both of which were observed on TOMM Trial 1. This data supports the recommendation that p < .20 be used when determining below chance performance.