Verbal Discrimination Task Research Articles

Hemodynamic matrix factorization for functional magnetic resonance imaging

The General Linear Model (GLM) used in task-fMRI relates activated brain areas to extrinsic task conditions. The translation of resulting neural activation into a hemodynamic response is commonly approximated with a linear convolution model using a hemodynamic response function (HRF). There are two major limitations in GLM analysis. Firstly, the GLM assumes that neural activation is either on or off and matches the exact stimulus duration in the corresponding task timings. Secondly, brain networks observed in resting-state fMRI experiments present also during task experiments, but the GLM approach models these task-unrelated brain activity as noise. A novel kernel matrix factorization approach, called hemodynamic matrix factorization (HMF), is therefore proposed that addresses both limitations by assuming that task-related and task-unrelated brain activity can be modeled with the same convolution model as in GLM analysis. By contrast to the GLM, the proposed HMF is a blind source separation (BSS) technique, which decomposes fMRI data into modes. Each mode comprises of a neural activation time course and a spatial mapping. Two versions of HMF are proposed in which the neural activation time course of each mode is convolved with either the canonical HRF or predetermined subject-specific HRFs.Firstly, HMF with the canonical HRF is applied to two open-source cohorts. These cohorts comprise of several task experiments including motor, incidental memory, spatial coherence discrimination, verbal discrimination task and a very short localization task, engaging multiple parts of the eloquent cortex. HMF modes were obtained whose neural activation time course followed original task timings and whose corresponding spatial map matched cortical areas known to be involved in the respective task processing.Secondly, the alignment of these neural activation time courses to task timings were further improved by replacing the canonical HRF with subject-specific HRFs during HMF mode computation.In addition to task-related modes, HMF also produced seemingly task-unrelated modes whose spatial maps matched known resting-state networks.The validity of a fMRI task experiment relies on the assumption that the exposure to a stimulus for a given time causes an imminent increase in neural activation of equal duration. The proposed HMF is an attempt to falsify this assumption and allows to identify subject task participation that does not comply with the experiment instructions.

Postmenopausal hormone treatment alters neural pathways but does not improve verbal cognitive function.

Cognitive outcomes in trials of postmenopausal hormone treatment have been inconsistent. Differing outcomes may be attributed to hormone formulation, treatment duration and timing, and differential cognitive domain effects. We previously demonstrated treatment benefits on visual cognitive function. In the present study, we describe the effects of hormone treatment on verbal outcomes in the same women, seeking to understand the effects of prior versus current hormone treatment on verbal function. This is a cross-sectional evaluation of 57 women (38 hormone users [25 prior long-term users and 13 current users] and 19 never-users). Hormone users took identical formulations of estrogen or estrogen + progestin (0.625 mg/d conjugated equine estrogens with or without medroxyprogesterone acetate) for at least 10 years, beginning within 2 years of menopause. Women were evaluated with tests of verbal function and functional magnetic resonance imaging (fMRI) of a verbal discrimination task. All women scored similarly on assessments of verbal function (Hopkins Verbal Learning Test and a verbal discrimination task performed during the fMRI scanning session); however, women ever treated with hormones had more left inferior frontal (T = 3.72; P < 0.001) and right prefrontal cortex (T = 3.53; P < 0.001) activation during the verbal task. Hormone-treated women performed slightly worse on the verbal discrimination task (mean accuracy 81.72 ± 11.57 ever-treated, 85.30 ± 5.87 never-treated, P = 0.14), took longer to respond (mean reaction time 1.10 ± 0.17 s ever-treated, 1.02 ± 0.11 never-treated, P = 0.03), and remembered fewer previously viewed words (mean accuracy 62.21 ± 8.73 ever-treated, 65.45 ± 7.49 never-treated, P = 0.18). Increased posterior cingulate activity was associated with longer response times (R = 0.323, P = 0.015) and worse delayed verbal recall (R = -0.328, P = 0.048), suggesting that increased activation was associated with less efficient cognitive processing. We did not detect between group differences in activation in the left prefrontal cortex, superior frontal cortex, thalamus, or occipital/parietal junction. Although current and past hormone treatment was associated with differences in neural pathways used during verbal discrimination, verbal function was not higher than never-users.

Buffered forgetting: When targets and distractors are both forgotten

In three experiments, we investigated prior findings that, following some memory tasks, essentially flat d' or forced-choice retention curves are produced. These curves have been interpreted as indicating that forgetting is not present over the intervals examined; however, we propose in this article that forgetting is actually present whenever hit rates and false alarm rates are both declining, despite the result being a flat retention curve. We demonstrate that such curves can be produced using a pair recognition procedure, a plurality discrimination task, and a verbal discrimination task. For all of these tasks, we provide either new evidence or refer to evidence already in the literature that tends to contradict alternative explanations. Then we show how the failure to consider both signal strength and noise has led to distortions in theoretical thinking about forgetting.

Individual differences in auditory cortex activation are related to the performance in a verbal auditory discrimination task

Individual differences in auditory cortex activation are related to the performance in a verbal auditory discrimination task

Preserved performance by cerebellar patients on tests of word generation, discrimination learning, and attention.

Recent theories suggest that the human cerebellum may contribute to the performance of cognitive tasks. We tested a group of adult patients with cerebellar damage attributable to stroke, tumor, or atrophy on four experiments involving verbal learning or attention shifting. In experiment 1, a verb generation task, participants produced semantically related verbs when presented with a list of nouns. With successive blocks of practice responding to the same set of stimuli, both groups, including a subset of cerebellar patients with unilateral right hemisphere lesions, improved their response times. In experiment 2, a verbal discrimination task, participants learned by trial and error to pick the target words from a set of word pairs. When age was taken into account, there were no performance differences between cerebellar patients and control subjects. In experiment 3, measures of spatial attention shifting were obtained under both exogenous and endogenous cueing conditions. Cerebellar patients and control subjects showed similar costs and benefits in both cueing conditions and at all SOAs. In experiment 4, intra- and interdimensional shifts of nonspatial attention were elicited by presenting word cues before the appearance of a target. Performance was substantially similar for cerebellar patients and control subjects. These results are presented as a cautionary note. The experiments failed to provide support for current hypotheses regarding the role of the cerebellum in verbal learning or attention. Alternative interpretations of previous results are discussed.

Single-item recognition following verbal discrimination study and/or test trials.

This experiment assessed further single-item recognition following verbal discrimination learning by varying the number of study and test trials presented during the initial verbal discrimination task. Two study periods (1 and 2 study trials) and three test periods (0, 1, and 2 trials) were factorially combined to yield six experimental groups. Increasing the test periods increased recognition of the prior words to be verbally discriminated as old items. Although subjects could identify the prior function of the old items, the variables did not increase or decrease this ability.

An Examination of the Rule-Use Construct of the Frequency Theory of Verbal Discrimination Learning

Summary Sixty-six female and 18 male college students were employed in a study of the relative effect of instructional set and item familiarity on performance in a 20-word pair, verbal discrimination task. Results indicated performance was facilitated with a 2:1 frequency ratio of correct to incorrect items (p < .001), but the instructions and interaction effects were nonsignificant. The results were discussed in terms of overt and covert rehearsal of word pairs.

The Relative Effectiveness of Rules 1 and 2 in Verbal Discrimination Learning

The prediction, derived from frequency theory, that performance on a verbal discrimination task would be the same for Rules 1 and 2 was tested. Appropriateness of the rules was achieved by varying the number of times the right (R) and wrong (W) items were pronounced during the feedback interval. The sequence of pronunciation (R-W or W-R) was also manipulated in order to determine whether rehearsal depends on the order of pronunciation. After the task was completed, each subject was given a modified free-recall task to investigate possible relationships between the various treatment conditions and incidental learning. Analyses of the data revealed a significant differential pronunciation effect (p < .05) indicating that Rule 2 responding retarded acquisition rate. Superior performance on the modified free-recall task was associated with a W-R, relative to an R-W, sequence of pronunciation during feedback. Discussion of the results indicated possible explanations inconsistent with frequency theory predictions.

Class of initial letter as a cue to correctness in verbal discrimination

In a verbal discrimination task, each pair consisted of a word beginning with a vowel (A, E, 0, or U) paired with a word beginning with a consonant (C, F, G, or S). When all the initial-vowel words were correct, performance was significantly better than when correctness was randomly determined. When all the initial-consonant words were correct, performance was not significantly different from the random control. Awareness of (i.e., ability to verbalize) the initial-vowel rule was not necessary for its effective utilization during VD learning, but only those few subjects who could verbalize the rule showed evidence of generalizing it to new words.

Item recognition following a multiple-item study trial for young and middle-aged adults

The presence study contrasted young and middle-aged subjects on two components of a recognition memory task (a modified verbal discrimination task) that differed in level of difficulty. No age decrement was found for the easier component requiring discriminability between the oldness and newness of items. In addition, age was not a factor in determining the effects of prior relevance or irrelevance of item information on old-new discriminability. An age decrement was found for the more difficult component requiring discriminability in terms of an old item's prior function in the study list. The decrement occurred for the identification of prior function of both right and wrong items.

Contingent associations and the double-function, verbal-discrimination task

Three experiments examined the role of contingent associations in learning double-function, verbal-discrimination lists. Some 15-pair lists of category instances were constructed in such a way that the learning of three contingent associations based on category names would mediate correct performance for all 15 pairs. The first experiment gave no evidence that the three contingencies aided learning. The second experiment showed that subjects could be taught the three contingent associations in isolation and that they could then apply them successfully to the double-function list. To make the contingencies more apparent to the subjects, the category names were used during feedback in the third experiment. The learning was not facilitated by such feedback. It was concluded that the learning observed for the usual double-function list does not involve contingent associations.

Mixed-list manipulations of implicit associative responses in verbal discrimination learning: II. Strategies and interactions with rate of presentation

Implicit associative responses were manipulated in a verbal discrimination task involving a mixed list of intrapair, interpair, interitem-AR, and control conditions in combination with three rates of presentation (1:1, 2:2, and 4:4 sec). The intrapair condition was significantly superior to the control at all three presentation rates. The interpair condition was inferior to the control at the 1:1 sec rate, equal to the control at the 2:2 rate, and superior at the 4:4 rate. The interitem—AR condition was equal to the control at the 1:1 sec rate, but superior at the 2:2 and 4:4 rates. The results were interpreted as consistent with the hypothesis that multiple higher order strategies may be invoked in such a mixed list design and that these strategies differ in levels of complexity, resulting in a complex interaction with rate of presentation.

Verbal-discrimination learning as a function of encoding variability

The encoding variability of the right (R) and wrong (W) terms was manipulated in a verbal-discrimination task. When the number of different associates defined variability, pairs with low-encoding variability for both R and W terms were learned fastest, followed by pairs with high-encoding variability in both R and W terms. When the number of dictionary meanings defined variability, pairs with high-encoding variability R terms and W terms were learned slower than all other combinations. The outcomes do not correspond to expectations involving only the number of encodings in each component of a pair; it is suggested that the number of nonoverlapping encodings is more important.

Mixed- list manipulations of implicit associative responses in verbal discrimination learning

Implicit associative responses were manipulated in a verbal discrimination task involving mixed-list of (a) pairs containing associatively related wrong (W) and right (R) items (intrapair condition), (b) associatively related W and R items in different pairs (interpair condition), (c) associatively related R items (interitem-AR condition), and (d) pairs involving no associative relationships (control condition). In agreement with frequency theory, the interitem-AR condition resulted in pronounced facilitation in acquisition relative to the control and interpair conditions, a result not consistently found with unmixed lists. Consistent with the “tagging” model but contrary to frequency theory, the intrapair condition was also significantly superior to the control and interpair conditions. The control and interpair conditions did not differ, suggesting that the interference usually found in the interpair condition in unmixed lists may be largely inhibited under the present mixed-list conditions.

Frequency and coding responses in verbal discrimination learning

Ss were given a verbal discrimination task where correct and incorrect stimuli appeared in one, two. or four different pairs in a within-Ss design. For a group tested with the usual anticipation procedure, correct repetitions helped and incorrect repetitions hurt performance. The pattern of results suggested that frequency is a salient cue in verbal discrimination learning but that coding or paired-associate processing may occur at the same time. Data from a second group of Ss for which frequency was a less salient cue gave more direct evidence for coding.

Verbal discrimination task performance as a function of self versus external reinforcement, I-E scale performance, and subject versus experimenter determination of response.

Summary One hundred forty-four subjects dichotomized as internal or external on the I-E scale were randomly assigned to one of three reinforcement conditions-no reinforcement, self-reinforcement, or external reinforcement-and one of three subject determination of the correct response conditions-0%, 50%, or 100%. Trials to criterion and errors to criterion on a complex verbal discrimination task were the dependent variables. The results demonstrated that self-reinforcement influenced learning to a greater degree than no reinforcement. Further, when subjects were allowed to determine 100% of the correct responses, the effects of self-reinforcement paralleled the effects of external reinforcement. When subjects determined 50% or 0% of the correct responses, the self-reinforcement and no reinforcement conditions did not differ in influencing overall rate of learning. Internals made significantly fewer errors than externals.

The effect of frequency and number of pairs in a verbal discrimination task

The assumption, derived from the frequency theory of verbal discrimination learning, that list length does not affect verbal discrimination learning proficiency was tested. Results indicated that (a) the number of correct items to be learned does affect learning proficiency significantly when the differential frequency cue is held constant; (b) previous findings reported by Ekstrand, Wallace, and Underwood (1966), that a 20-pair list involving 10 right items repeated twice is superior to a 20-pair control group with no repeated items. may have been due, at least in part, to the fewer number of items to be learned and not solely to the larger differential frequency cue.

Verbal Discrimination: Re-Pairing, Language Frequency, and Associative Properties of the Stimuli

Four experiments provide evidence that (a) language frequency of the stimuli can influence the rate of learning of a verbal discrimination, (b) re-pairing of the 'correct' and 'incorrect' members of pairs has little effect if introduced from the outset but produces performance decrements if introduced when the list is nearly learned, (c) these re-pairing decrements occur differentially for lists that differ in preexperimental interitem associations, and (d) the intrapair associations formed during the learning of a verbal-discrimination task are not incidental to performance on that task. The present paper reports the results of four experiments on verbaldiscrimination learning. These experiments manipulated the associative properties and the language frequency of stimuli, as well as the pairings of 'right' and 'wrong' items within a list. In a typical verbal-discrimination task, the subject is successively presented pairs of verbal items and must learn which member of each pair has been arbitrarily designated as correct by the experimenter; the pairing of items is constant, but the positions of an item within the pair and of a pair within the list vary from trial to trial. According to the frequency theory of verbal-discrimination learning (Ekstrand, Wallace, and Underwood, 1966), the subject performs this task by discriminating between the subjective frequencies accrued to the 'correct' and 'incorrect' members of each pair in the experimental setting. An item gains frequency increments as a consequence of being seen, given as an overt response, or covertly rehearsed. Correct items build up frequency faster than incorrect items, and the subject comes to be able to respond without error by applying this strategy to all pairs: 'Choose the member with the greater subjective frequency.' If the frequency theory is correct and the subject indeed discriminates between the subjective frequencies elicited by the two members of the pair, rather than between, say, any semantic properties of the words

The effects of physical and psychological stress on the performance of high- and low-anxious Ss on a difficult verbal discrimination task

The effects of shock and ego-involving IQ-oriented instructions on the performance of high-anxious (HA) and low-anxious (LA) Ss on a difficult low-imagery verbal discrimination task were investigated. As predicted by Saltz’s differential disruption hypothesis, LA Ss made significantly more errors than HA Ss in the shock condition, and HA Ss made significantly more errors in the control condition. However, no significant difference in performance was found between HA and LA Ss in the ego-involving condition. The results were interpreted as generally supportive of Saltz’s view that HA and LA Ss are sensitive to different sources of stress.

Retroactive Inhibition and Spontaneous Recovery in a Contingent Verbal Discrimination Task

A primary purpose of the present experiment was to examine retroactive inhibition and spontaneous recovery by employing a task which combines aspects of paired-associate and verbal-discrimination learning. The design was a 3 × 2 independent groups factorial manipulating type of interpolated learning and length of the retention interval. There were 14 Ss in each of the six groups. Significant retroactive inhibition was found in one condition and an absolute temporal increase in List-1 recall in another; however, the interaction of Condition × Retention Interval was not significant. Acquisition and recall data are discussed primarily in terms of frequency theory and response-set interference.