Darlene Howard - Academia.edu (original) (raw)

Papers by Darlene Howard

Research paper thumbnail of Physical Activity Is Associated with Reduced Implicit Learning but Enhanced Relational Memory and Executive Functioning in Young Adults

PloS one, 2016

Accumulating evidence suggests that physical activity improves explicit memory and executive cogn... more Accumulating evidence suggests that physical activity improves explicit memory and executive cognitive functioning at the extreme ends of the lifespan (i.e., in older adults and children). However, it is unknown whether these associations hold for younger adults who are considered to be in their cognitive prime, or for implicit cognitive functions that do not depend on motor sequencing. Here we report the results of a study in which we examine the relationship between objectively measured physical activity and (1) explicit relational memory, (2) executive control, and (3) implicit probabilistic sequence learning in a sample of healthy, college-aged adults. The main finding was that physical activity was positively associated with explicit relational memory and executive control (replicating previous research), but negatively associated with implicit learning, particularly in females. These results raise the intriguing possibility that physical activity upregulates some cognitive pro...

Research paper thumbnail of Cognitive psychology : memory, language, and thought

Research paper thumbnail of Sleep has no critical role in implicit motor sequence learning in young and old adults

Experimental Brain Research, 2010

The inXuence of sleep on motor skill consolidation has been a research topic of increasing intere... more The inXuence of sleep on motor skill consolidation has been a research topic of increasing interest. In this study, we distinguished general skill learning from sequence-speciWc learning in a probabilistic implicit sequence learning task (alternating serial reaction time) in young and old adults before and after a 12-h oZine interval which did or did not contain sleep (p.m.-a.m. and a.m.-p.m. groups, respectively). The results showed that general skill learning, as assessed via overall reaction time, improved oZine in both the young and older groups, with the young group improving more than the old. However, the improvement was not sleep-dependent, in that there was no diVerence between the a.m.-p.m. and p.m.-a.m. groups. We did not Wnd sequence-speciWc oZine improvement in either age group for the a.m.-either p.m. or p.m.-a.m. groups, suggesting that consolidation of this kind of implicit motor sequence learning may not be inXuenced by sleep.

Research paper thumbnail of Aging and the Statistical Learning of Grammatical Form Classes

Psychology and Aging, 2016

Language learners must place unfamiliar words into categories, often with few explicit indicators... more Language learners must place unfamiliar words into categories, often with few explicit indicators about when and how that word can be used grammatically. Reeder, Newport, and Aslin (2013) showed that college students can learn grammatical form classes from an artificial language by relying solely on distributional information (i.e., contextual cues in the input). Here, 2 experiments revealed that healthy older adults also show such statistical learning, though they are poorer than young at distinguishing grammatical from ungrammatical strings. This finding expands knowledge of which aspects of learning vary with aging, with potential implications for second language learning in late adulthood. (PsycINFO Database Record

Research paper thumbnail of A multidimensional scaling analysis of the development of animal names

Developmental Psychology, 1977

... Presuma-bly, then, the features are changing, despite the fact that most adolescents make vir... more ... Presuma-bly, then, the features are changing, despite the fact that most adolescents make virtually no referential errors with the words in ques-tion. ... Psychological Review, 1974,81, 214-241. Weiner, SL On the development of more and less. ...

Research paper thumbnail of Implicit sequence learning without motor sequencing in young and old adults

Experimental Brain Research, Jun 20, 2006

The ability to detect patterns and organize individual events into complex sequences is a fundame... more The ability to detect patterns and organize individual events into complex sequences is a fundamental cognitive skill that is often learned implicitly. The serial response time (SRT) task has been widely used to investigate implicit sequence learning, but it remains unclear whether people learn a perceptual or motor sequence in this task. This study reports three experiments that build on previous research by Goschke and colleagues using an auditory SRT task in which the stimulus-to-response mapping changes on every trial to eliminate spatio-motor sequencing. The current study extends earlier work in three ways. First, healthy young and older adults were tested rather than the neuropsychological patients used in previous research. Second, sequences of diVerent structural complexity were investigated including Wrstand second-order repeating sequences as well as higher-order probabilistic sequences. Third, the potential role of explicit knowledge was examined using three separate tests of declarative knowledge. Results indicate that young and old adults are able to learn purely perceptual auditory sequences, but that explicit knowledge contributes to learning of repeating sequences by young adults.

Research paper thumbnail of Implicit Learning of Visuospatial Sequences in Schizophrenia

Neuropsychology, Aug 1, 2003

Research paper thumbnail of Japanese-English Bilingualism Influences Control of Attention but Not Implicit Sequence Learning

The results of the Simon Task were consistent with previous studies of bilinguals, and extend the... more The results of the Simon Task were consistent with previous studies of bilinguals, and extend these results to Japanese speakers. The bilingual group displayed a significantly smaller Simon effect than the monolingual group, showing greater attentional control (Bialystok et al., 2004; Romano et al., 2007). However, there was no significant difference among the groups on the implicit learning task, which was also consistent with the previous study by Romano et al. (2007) with Spanish-English bilinguals. Japanese-English bilinguals showed significantly better performance compared to English monolinguals on the shortterm memory and working memory tasks (Digit Span, Spatial Span, Digit Symbol Pairing and Free Recall and Consonant Trigrams) and Vocabulary. There was no difference between the two groups on logical reasoning (Matrix Reasoning), and visual-motor speed (Digit Symbol Coding). In summary, we found that Japanese-English bilingualism was associated with better attentional control and enhanced short-term and working memory, but not with better implicit sequence learning.

Research paper thumbnail of A multidimensional scaling analysis of aging and the semantic structure of animal names

Exp Aging Res, 1983

Adult age differences in semantic structure were investigated using nonmetric individual differen... more Adult age differences in semantic structure were investigated using nonmetric individual differences multidimensional scaling. Similarity judgments of all possible pairs of 16 animal names were obtained from 20 adults in each of the following six age ranges: 20-29, 30-39, 40-49, 50-59, 60-69, 70-79. The overall scaling solution revealed a semantic space consisting of the features of size and predativity. Comparisons of the age groups revealed a small but statistically significant tendency for participants in the two oldest groups to emphasize the concrete dimension of size, in contrast with the middle-aged groups who emphasized the abstract dimension of predativity. This abstract-to-concrete trend of adult age differences is compared with the concrete-to-abstract trend for this same semantic domain which has been observed previously among young children.

Research paper thumbnail of Implicit Higher-Order Sequence Learning by Event Observation

Method We previously found that simple repeating sequences can be learned by observation without ... more Method We previously found that simple repeating sequences can be learned by observation without responding. Here we investigate if observational learning occurs in sequences with higher-order, probabilistic structure. Results show that students who ...

Research paper thumbnail of EEG Alpha Desynchronization is Related to Implicit Learning in the Triplets Learning Task

Research paper thumbnail of Search and decision processes in intentional forgetting: A reaction time analysis

Journal of Experimental Psychology: Human Learning & Memory, 1976

ABSTRACT

Research paper thumbnail of Implicit and Explicit Assessment of Cognitive Aging

Springer Series in Cognitive Development, 1988

Research paper thumbnail of Relationship of Contextual Cueing and Hippocampal Volume in Amnestic Mild Cognitive Impairment Patients and Cognitively Normal Older Adults

Journal of the International Neuropsychological Society : JINS, Jan 20, 2015

There is currently some debate as to whether hippocampus mediates contextual cueing. In the prese... more There is currently some debate as to whether hippocampus mediates contextual cueing. In the present study, we examined contextual cueing in patients diagnosed with mild cognitive impairment (MCI) and healthy older adults, with the main goal of investigating the role of hippocampus in this form of learning. Amnestic MCI (aMCI) patients and healthy controls completed the contextual cueing task, in which they were asked to search for a target (a horizontal T) in an array of distractors (rotated L's). Unbeknownst to them, the spatial arrangement of elements on some displays was repeated thus making the configuration a contextual cue to the location of the target. In contrast, the configuration for novel displays was generated randomly on each trial. The difference in response times between repeated and novel configurations served as a measure of contextual learning. aMCI patients, as a group, were able to learn spatial contextual cues as well as healthy older adults. However, better...

Research paper thumbnail of When it does hurt to try: adult age differences in the effects of instructions on implicit pattern learning

Psychonomic bulletin & review, 2001

Trying to learn sometimes impairs implicit learning of artificial grammars and of control systems... more Trying to learn sometimes impairs implicit learning of artificial grammars and of control systems. We asked whether such negative effects of trying also occur in implicit learning of subtle sequential regularities and whether such effects vary with adult age. Young (n = 12, age = 20-23) and older (n = 24, age = 60-80) adults completed an alternating serial response time task in which predictable pattern events alternated with random ones in a visual/spatial display. Half of the participants were informed about the pattern and were instructed to try to discover it (intentional instructions), and half were not (incidental instructions). Age-related deficits in implicit learning occurred for both conditions. In addition, for the older group, but not for the younger one, intentional instructions impaired implicit pattern learning. This negative effect of trying to learn demonstrates another similarity among implicit learning tasks, supporting the view that some common processes underlie...

Research paper thumbnail of Semantic activation during memory encoding across the adult life span

Journal of gerontology, 1980

The hypothesis that automatic processes do not change during aging was investigated using Warren&... more The hypothesis that automatic processes do not change during aging was investigated using Warren's (1972) modification of the Stroop procedure. The subjects were 14 adults in each of three age groups: young (20 to 39), middle (40 to 59), and old (60 to 79). On each trial, subjects held three category members in memory while they named the ink color in which a base item was printed. For all three age groups, color naming latencies were longer when the base item was from the same category as the memory list items. According to network theories of long-term memory, these findings suggest that, throughout adulthood, holding words in working memory results in activation of the memory nodes corresponding to the words themselves, and also in activation spreading to semantically related nodes. The results are consistent with the hypothesis that acquired automatic processes do not deteriorate with aging.

Research paper thumbnail of Category norms: a comparison of the Battig and Montague (1969) norms with the responses of adults between the ages of 20 and 80

Journal of gerontology, 1980

In order to determine whether category norms collected from college students are appropriate for ... more In order to determine whether category norms collected from college students are appropriate for research with older adults, 25 men and 25 women in each of three age groups, Young (20 to 39 years), Middle (40 to 59 years) and Old (60 to 79 years), were asked to produce as many category members as possible for each of 21 categories chosen from those included in the Battig and Montague (1969) norms. The correlations between the responses of the present subjects and Battig and Montague's were high for all three age groups studied. It is concluded that for most of the categories studied here, it is appropriate to use the Battig and Montague norms when choosing stimuli for experiments with middle-aged and elderly adults. Additional analyses revealed that the Old group produced fewer responses per person per category than the Young and Middle groups. Analyses of between-subject variability indicated that the subjects in the Old group were less likely than the younger subjects to produ...

Research paper thumbnail of Semantic priming of lexical decisions in young and old adults

Journal of gerontology, 1981

Twenty-four young (M = 28 years) and 24 old (M = 70 years) adults completed a lexical decision ta... more Twenty-four young (M = 28 years) and 24 old (M = 70 years) adults completed a lexical decision task in which they saw two strings of letters on each trial and were asked to respond "yes" only if both strings were words. For both ages, decisions were faster when the words were associated than when they were not. This pattern emerged for both ages, regardless of whether the associated pairs were category-member or descriptive-property associates. The same participants were also presented with a list of words to free recall. There was a decline with age both in the number of words recalled and in the degree of categorical clustering, particularly of low frequency category exemplars. Viewed from the perspective of two-process semantic activation models, these results place constraints on processing-deficit theories, and are consistent with the hypothesis that effortful processes change with aging, whereas automatic processes do not.

Research paper thumbnail of A multidimensional scaling analysis of aging and the semantic structure of animal names

Experimental aging research, 1983

Adult age differences in semantic structure were investigated using nonmetric individual differen... more Adult age differences in semantic structure were investigated using nonmetric individual differences multidimensional scaling. Similarity judgments of all possible pairs of 16 animal names were obtained from 20 adults in each of the following six age ranges: 20-29, 30-39, 40-49, 50-59, 60-69, 70-79. The overall scaling solution revealed a semantic space consisting of the features of size and predativity. Comparisons of the age groups revealed a small but statistically significant tendency for participants in the two oldest groups to emphasize the concrete dimension of size, in contrast with the middle-aged groups who emphasized the abstract dimension of predativity. This abstract-to-concrete trend of adult age differences is compared with the concrete-to-abstract trend for this same semantic domain which has been observed previously among young children.

Research paper thumbnail of Are differential orienting responses necessary for dimensional learning and transfer?

Journal of experimental psychology, 1973

ABSTRACT

Research paper thumbnail of Physical Activity Is Associated with Reduced Implicit Learning but Enhanced Relational Memory and Executive Functioning in Young Adults

PloS one, 2016

Accumulating evidence suggests that physical activity improves explicit memory and executive cogn... more Accumulating evidence suggests that physical activity improves explicit memory and executive cognitive functioning at the extreme ends of the lifespan (i.e., in older adults and children). However, it is unknown whether these associations hold for younger adults who are considered to be in their cognitive prime, or for implicit cognitive functions that do not depend on motor sequencing. Here we report the results of a study in which we examine the relationship between objectively measured physical activity and (1) explicit relational memory, (2) executive control, and (3) implicit probabilistic sequence learning in a sample of healthy, college-aged adults. The main finding was that physical activity was positively associated with explicit relational memory and executive control (replicating previous research), but negatively associated with implicit learning, particularly in females. These results raise the intriguing possibility that physical activity upregulates some cognitive pro...

Research paper thumbnail of Cognitive psychology : memory, language, and thought

Research paper thumbnail of Sleep has no critical role in implicit motor sequence learning in young and old adults

Experimental Brain Research, 2010

The inXuence of sleep on motor skill consolidation has been a research topic of increasing intere... more The inXuence of sleep on motor skill consolidation has been a research topic of increasing interest. In this study, we distinguished general skill learning from sequence-speciWc learning in a probabilistic implicit sequence learning task (alternating serial reaction time) in young and old adults before and after a 12-h oZine interval which did or did not contain sleep (p.m.-a.m. and a.m.-p.m. groups, respectively). The results showed that general skill learning, as assessed via overall reaction time, improved oZine in both the young and older groups, with the young group improving more than the old. However, the improvement was not sleep-dependent, in that there was no diVerence between the a.m.-p.m. and p.m.-a.m. groups. We did not Wnd sequence-speciWc oZine improvement in either age group for the a.m.-either p.m. or p.m.-a.m. groups, suggesting that consolidation of this kind of implicit motor sequence learning may not be inXuenced by sleep.

Research paper thumbnail of Aging and the Statistical Learning of Grammatical Form Classes

Psychology and Aging, 2016

Language learners must place unfamiliar words into categories, often with few explicit indicators... more Language learners must place unfamiliar words into categories, often with few explicit indicators about when and how that word can be used grammatically. Reeder, Newport, and Aslin (2013) showed that college students can learn grammatical form classes from an artificial language by relying solely on distributional information (i.e., contextual cues in the input). Here, 2 experiments revealed that healthy older adults also show such statistical learning, though they are poorer than young at distinguishing grammatical from ungrammatical strings. This finding expands knowledge of which aspects of learning vary with aging, with potential implications for second language learning in late adulthood. (PsycINFO Database Record

Research paper thumbnail of A multidimensional scaling analysis of the development of animal names

Developmental Psychology, 1977

... Presuma-bly, then, the features are changing, despite the fact that most adolescents make vir... more ... Presuma-bly, then, the features are changing, despite the fact that most adolescents make virtually no referential errors with the words in ques-tion. ... Psychological Review, 1974,81, 214-241. Weiner, SL On the development of more and less. ...

Research paper thumbnail of Implicit sequence learning without motor sequencing in young and old adults

Experimental Brain Research, Jun 20, 2006

The ability to detect patterns and organize individual events into complex sequences is a fundame... more The ability to detect patterns and organize individual events into complex sequences is a fundamental cognitive skill that is often learned implicitly. The serial response time (SRT) task has been widely used to investigate implicit sequence learning, but it remains unclear whether people learn a perceptual or motor sequence in this task. This study reports three experiments that build on previous research by Goschke and colleagues using an auditory SRT task in which the stimulus-to-response mapping changes on every trial to eliminate spatio-motor sequencing. The current study extends earlier work in three ways. First, healthy young and older adults were tested rather than the neuropsychological patients used in previous research. Second, sequences of diVerent structural complexity were investigated including Wrstand second-order repeating sequences as well as higher-order probabilistic sequences. Third, the potential role of explicit knowledge was examined using three separate tests of declarative knowledge. Results indicate that young and old adults are able to learn purely perceptual auditory sequences, but that explicit knowledge contributes to learning of repeating sequences by young adults.

Research paper thumbnail of Implicit Learning of Visuospatial Sequences in Schizophrenia

Neuropsychology, Aug 1, 2003

Research paper thumbnail of Japanese-English Bilingualism Influences Control of Attention but Not Implicit Sequence Learning

The results of the Simon Task were consistent with previous studies of bilinguals, and extend the... more The results of the Simon Task were consistent with previous studies of bilinguals, and extend these results to Japanese speakers. The bilingual group displayed a significantly smaller Simon effect than the monolingual group, showing greater attentional control (Bialystok et al., 2004; Romano et al., 2007). However, there was no significant difference among the groups on the implicit learning task, which was also consistent with the previous study by Romano et al. (2007) with Spanish-English bilinguals. Japanese-English bilinguals showed significantly better performance compared to English monolinguals on the shortterm memory and working memory tasks (Digit Span, Spatial Span, Digit Symbol Pairing and Free Recall and Consonant Trigrams) and Vocabulary. There was no difference between the two groups on logical reasoning (Matrix Reasoning), and visual-motor speed (Digit Symbol Coding). In summary, we found that Japanese-English bilingualism was associated with better attentional control and enhanced short-term and working memory, but not with better implicit sequence learning.

Research paper thumbnail of A multidimensional scaling analysis of aging and the semantic structure of animal names

Exp Aging Res, 1983

Adult age differences in semantic structure were investigated using nonmetric individual differen... more Adult age differences in semantic structure were investigated using nonmetric individual differences multidimensional scaling. Similarity judgments of all possible pairs of 16 animal names were obtained from 20 adults in each of the following six age ranges: 20-29, 30-39, 40-49, 50-59, 60-69, 70-79. The overall scaling solution revealed a semantic space consisting of the features of size and predativity. Comparisons of the age groups revealed a small but statistically significant tendency for participants in the two oldest groups to emphasize the concrete dimension of size, in contrast with the middle-aged groups who emphasized the abstract dimension of predativity. This abstract-to-concrete trend of adult age differences is compared with the concrete-to-abstract trend for this same semantic domain which has been observed previously among young children.

Research paper thumbnail of Implicit Higher-Order Sequence Learning by Event Observation

Method We previously found that simple repeating sequences can be learned by observation without ... more Method We previously found that simple repeating sequences can be learned by observation without responding. Here we investigate if observational learning occurs in sequences with higher-order, probabilistic structure. Results show that students who ...

Research paper thumbnail of EEG Alpha Desynchronization is Related to Implicit Learning in the Triplets Learning Task

Research paper thumbnail of Search and decision processes in intentional forgetting: A reaction time analysis

Journal of Experimental Psychology: Human Learning & Memory, 1976

ABSTRACT

Research paper thumbnail of Implicit and Explicit Assessment of Cognitive Aging

Springer Series in Cognitive Development, 1988

Research paper thumbnail of Relationship of Contextual Cueing and Hippocampal Volume in Amnestic Mild Cognitive Impairment Patients and Cognitively Normal Older Adults

Journal of the International Neuropsychological Society : JINS, Jan 20, 2015

There is currently some debate as to whether hippocampus mediates contextual cueing. In the prese... more There is currently some debate as to whether hippocampus mediates contextual cueing. In the present study, we examined contextual cueing in patients diagnosed with mild cognitive impairment (MCI) and healthy older adults, with the main goal of investigating the role of hippocampus in this form of learning. Amnestic MCI (aMCI) patients and healthy controls completed the contextual cueing task, in which they were asked to search for a target (a horizontal T) in an array of distractors (rotated L's). Unbeknownst to them, the spatial arrangement of elements on some displays was repeated thus making the configuration a contextual cue to the location of the target. In contrast, the configuration for novel displays was generated randomly on each trial. The difference in response times between repeated and novel configurations served as a measure of contextual learning. aMCI patients, as a group, were able to learn spatial contextual cues as well as healthy older adults. However, better...

Research paper thumbnail of When it does hurt to try: adult age differences in the effects of instructions on implicit pattern learning

Psychonomic bulletin & review, 2001

Trying to learn sometimes impairs implicit learning of artificial grammars and of control systems... more Trying to learn sometimes impairs implicit learning of artificial grammars and of control systems. We asked whether such negative effects of trying also occur in implicit learning of subtle sequential regularities and whether such effects vary with adult age. Young (n = 12, age = 20-23) and older (n = 24, age = 60-80) adults completed an alternating serial response time task in which predictable pattern events alternated with random ones in a visual/spatial display. Half of the participants were informed about the pattern and were instructed to try to discover it (intentional instructions), and half were not (incidental instructions). Age-related deficits in implicit learning occurred for both conditions. In addition, for the older group, but not for the younger one, intentional instructions impaired implicit pattern learning. This negative effect of trying to learn demonstrates another similarity among implicit learning tasks, supporting the view that some common processes underlie...

Research paper thumbnail of Semantic activation during memory encoding across the adult life span

Journal of gerontology, 1980

The hypothesis that automatic processes do not change during aging was investigated using Warren&... more The hypothesis that automatic processes do not change during aging was investigated using Warren's (1972) modification of the Stroop procedure. The subjects were 14 adults in each of three age groups: young (20 to 39), middle (40 to 59), and old (60 to 79). On each trial, subjects held three category members in memory while they named the ink color in which a base item was printed. For all three age groups, color naming latencies were longer when the base item was from the same category as the memory list items. According to network theories of long-term memory, these findings suggest that, throughout adulthood, holding words in working memory results in activation of the memory nodes corresponding to the words themselves, and also in activation spreading to semantically related nodes. The results are consistent with the hypothesis that acquired automatic processes do not deteriorate with aging.

Research paper thumbnail of Category norms: a comparison of the Battig and Montague (1969) norms with the responses of adults between the ages of 20 and 80

Journal of gerontology, 1980

In order to determine whether category norms collected from college students are appropriate for ... more In order to determine whether category norms collected from college students are appropriate for research with older adults, 25 men and 25 women in each of three age groups, Young (20 to 39 years), Middle (40 to 59 years) and Old (60 to 79 years), were asked to produce as many category members as possible for each of 21 categories chosen from those included in the Battig and Montague (1969) norms. The correlations between the responses of the present subjects and Battig and Montague's were high for all three age groups studied. It is concluded that for most of the categories studied here, it is appropriate to use the Battig and Montague norms when choosing stimuli for experiments with middle-aged and elderly adults. Additional analyses revealed that the Old group produced fewer responses per person per category than the Young and Middle groups. Analyses of between-subject variability indicated that the subjects in the Old group were less likely than the younger subjects to produ...

Research paper thumbnail of Semantic priming of lexical decisions in young and old adults

Journal of gerontology, 1981

Twenty-four young (M = 28 years) and 24 old (M = 70 years) adults completed a lexical decision ta... more Twenty-four young (M = 28 years) and 24 old (M = 70 years) adults completed a lexical decision task in which they saw two strings of letters on each trial and were asked to respond "yes" only if both strings were words. For both ages, decisions were faster when the words were associated than when they were not. This pattern emerged for both ages, regardless of whether the associated pairs were category-member or descriptive-property associates. The same participants were also presented with a list of words to free recall. There was a decline with age both in the number of words recalled and in the degree of categorical clustering, particularly of low frequency category exemplars. Viewed from the perspective of two-process semantic activation models, these results place constraints on processing-deficit theories, and are consistent with the hypothesis that effortful processes change with aging, whereas automatic processes do not.

Research paper thumbnail of A multidimensional scaling analysis of aging and the semantic structure of animal names

Experimental aging research, 1983

Adult age differences in semantic structure were investigated using nonmetric individual differen... more Adult age differences in semantic structure were investigated using nonmetric individual differences multidimensional scaling. Similarity judgments of all possible pairs of 16 animal names were obtained from 20 adults in each of the following six age ranges: 20-29, 30-39, 40-49, 50-59, 60-69, 70-79. The overall scaling solution revealed a semantic space consisting of the features of size and predativity. Comparisons of the age groups revealed a small but statistically significant tendency for participants in the two oldest groups to emphasize the concrete dimension of size, in contrast with the middle-aged groups who emphasized the abstract dimension of predativity. This abstract-to-concrete trend of adult age differences is compared with the concrete-to-abstract trend for this same semantic domain which has been observed previously among young children.

Research paper thumbnail of Are differential orienting responses necessary for dimensional learning and transfer?

Journal of experimental psychology, 1973

ABSTRACT