Monday, December 2, 2013

Executive Functions: Inhibitory Control, Working Memory, and Cognitive Flexibility

Diamond, A. (2013). Executive Functions. Annual Review of Psychology, 64, 135–168.

Diamond refers to executive functions (EFs) as a “family” of mental processes necessary for concentrating or paying attention. In this review paper, Diamond walks through three core EFs: inhibitory control, working memory, and cognitive flexibility.

Inhibitory control is our ability to choose what to focus on while suppressing distractors or impulsive behaviours. Aspects include using self-control, staying on task, resisting temptation, and delaying gratification. These aspects can be assessed using a variety of behavioural measures. One example of a delayed gratification test is the marshmallow test, in which children are asked to choose between receiving one marshmallow now or two marshmallows if they wait.

Working memory, the ability to manipulate verbal or nonverbal material while holding it in mind, tends to work closely with inhibitory control. For example, working memory supports inhibitory control by holding the current goal in mind, which makes it easier to stay on task. Similarly, inhibitory control can support working memory by suppressing irrelevant ideas and decluttering our mental workspace. This overlap can make it difficult to separate working memory and inhibitory control, although some research with older adults is showing that the ability to suppress unwanted ideas or actions (i.e., inhibitory control) is separate from the ability to activate appropriate ideas or actions (i.e., working memory). Diamond notes the difficulty in assessing working memory, arguing that many tasks assess only the storage of information, whereas others go beyond the scope of working memory and require more subcomponents of EFs.

Cognitive flexibility allows for mental adaptability and versatility, such as thinking “outside the box,” seeing something from a different perspective, or switching tasks or priorities. A task commonly used to assess cognitive flexibility is a card sorting task. For this activity, subjects are given cards with images that could be sorted according to a few different features (e.g., colour of object , shape of object, background colour) and asked to sort them. Subjects may be asked to sort the cards based on trial-by-trial feedback they receive, or they may be asked to sort them according to one dimension first, and another later on.

Diamond notes that EFs are highly affected by stressors such as depressed mood, sleep deprivation, or insufficient exercise. She concludes by outlining five principles of effective intervention for EF: 1) those with lowest EF will benefit the most; 2) extent of transfer depends on the type of intervention; 3) demands on EF need to continually increase; 4) repetition is essential; 5) biggest differences between trial groups and control groups are seen on the most demanding tasks.

Blogger: Laura Pauls is a PhD student in Speech & Language Science, researching children with language impairment and/or working memory impairment.

Tuesday, November 12, 2013

Sentence processing: The role of memory and expectations in understanding relative clauses

Levy, R., Fedorenko, E., & Gibson, E. (2013). The syntactic complexity of Russian relative clauses. Journal of Memory and Language, 69, 461-495.

Human language is unique amongst communication systems because of its expressivity: We can hear a sentence we have never heard before and understand its meaning. But how does this happen? We do not have the memory resources to pursue every possible interpretation of a sentence, so there must be some sort of cognitive constraint that guides our understanding. Possible cognitive constraints have been investigated by examining how long it takes for people to understand or read sentences that present some confusion, that is, syntactic ambiguity resolution.

Research in processing relative clauses is important in understanding syntactic ambiguity resolution because these are one of the most complex sentence forms we encounter, and they offer an avenue to explore language’s rich expressive capacity. There are two types of relative clauses examined in this paper:

1)   Subject-extracted relative clause
The reporter who attacked the senator hoped for a story
            subject                 relative clause verb        object

2)   Object-extracted relative clause
The reporter who the senator attacked hoped for a story
                 object                                      subject  relative clause verb

The finding is that object relative clause sentences are more difficult to process than subject relative clause sentences. The authors distinguish between two theories that explain this difference in processing: Memory Based Theories and Expectation Based Theories. Memory Based Theories state that the comprehender is actively storing, integrating, and retrieving incoming information from the sentence in an online fashion. In these theories, the more material that needs to be processed, the more overloaded the memory system gets and the higher the processing load. Based on this theory, sentence 2 is harder to process because you need to hold more information in memory before you get to the verb attacked, which is the point where the meaning of the sentence becomes clear.
Expectation Based Theories assume that your previous language experience and semantic content shapes your sentence processing abilities. In fact, for Expectation Based Theories, greater semantic information (more words) in the sentence helps sharpen your expectations and guides your processing, whereas Memory Based Theories would predict that this impairs in processing. Based on this theory, sentence 2 is harder to process because it follows an Object-Subject-Word order. We are used to hearing Subject-Verb-Object orders in English, so this violates our expectations.

Even though the theories were difficult to disentangle in this paper, there are two interesting ideas in this paper: Memory limits may constrain language processing, and language processing may be limited by a lack of language knowledge. Considering which of these resources may be impacting language processing may help to understand a particular individual’s language functioning.

Blogger: Nicolette Noonan

Wednesday, November 6, 2013

Sensitivity to Word Order Cues by Normal and Language/Learning Disabled Adults

Plante, E., Gómez, R., & Gerken, L. A. (2002). Sensitivity to word order cues by normal and language/learning disabled adults. Journal of Communication Disorders, 35, 453–462.

The ability to recognize statistical regularities in inputs is considered to be an important learning mechanism emerging early in life and supporting language acquisition (Gómez & Gerken, 1999). Children with specific language impairment (SLI) on the other hand, have been found to have difficulty extracting statistical regularities from the input (Bishop, 1982).
In this article, Plante, Gómez, and Gerken (2002) examined statistical learning of sequential word order strings generated by an artificial grammar. Participants included 32 adults with and without personal or familial history of language/learning disabilities (L/LD). In the artificial grammar task, adults listened to novel consonant-vowel-consonant (CVC) words, with grammatical rules regarding syllable sequences for five minutes. After listening to the language, participants were asked to judge whether a new sentence spoken in the novel language obeys or violates the rules of the language.  After only five minutes of exposure to the training set, typically developing adults were able to exceed chance performance, whereas adults with L/LD showed significantly lower performance compared to the control group.

These results suggest that adults with L/LD may have difficulty in recognizing word order compared to typically developing adults. It may be adults with L/LD have more difficulty extracting the regularities available in linguistic input. Another study reviewed in this blog by Evans et al. (2009)  suggested that children with language impairment requirement more repetitions to learn the statistical patterns available in the input.

Blogger: Areej Balilah