Thursday, May 30, 2019

Rehearsal Effects in Adult Word Learning

Kaushanskaya, M., & Yoo, J. (2011). Rehearsal effects in adult word learning. Language and Cognitive Processes, 26(1), 121-148. doi:10.1080/01690965.2010.486579

Imagine you were trying to learn some useful Spanish words before travelling to Spain. You might start rehearsing the phrase ‘buenos días’ over and over again. This is one type of strategy people automatically use when learning new (foreign) words. By rehearsing the words, the novel phonological word form (speech sounds) is kept active in our minds using what’s called, ‘working memory’. Eventually, the word form is encoded (entered and stored) in long-term memory. There are two ways we might rehearse a word: (1) subvocal rehearsal (i.e., silent), that is just saying it in your head but not aloud and not moving your mouth, and (2) vocal rehearsal, that is saying the word out loud.  One of the goals of this study was to better understand how each of these processes support the learning of new words. Further, foreign words may contain sounds and/or sound structures that do not occur in English, such as /x/ in the Spanish word ‘ojo’ (meaning ‘eye’). Another goal of the study was to investigate how English-like words would benefit from rehearsal differently than words that contain non-native sounds. The also study wanted to examine how meaning is associated with learning novel words. This is important because learning a new word involves knowing both the phonological form and its associated meaning. Returning to the ‘buenos días’ example, it might be helpful to know that this means ‘good morning’ in English so that you can use it to greet people in the morning and not at night.

Across two experiments, adults who spoke only English learned novel words that followed the English structure (phonologically familiar) in Experiment 1 and novel words that contained non-native sounds (phonologically unfamiliar) in Experiment 2. Each word was paired with an English translation. Within each experiment, half of the words were learned through vocal rehearsal and the other half through subvocal rehearsal. Learning was assessed indirectly, that is, participants would hear the novel word and had to recall the English translation (recall task) or choose the correct English translation from five alternative words (recognition task). Testing was done immediately and one week later.

The results indicate that vocal rehearsal was beneficial for phonologically familiar words while subvocal rehearsal was beneficial for phonologically unfamiliar words when tested immediately. Interestingly, there was no difference at delayed testing, with weak rehearsal effects at minimum. The authors conclude that different rehearsal strategies may support learning in different ways. When saying aloud novel phonologically familiar words, this may highlight similarities between structures of novel words and English, and thereby, increase the learner’s ability to rely on native-language knowledge during learning. In contrast, saying aloud novel phonologically unfamiliar words may highlight differences and deter learning. Instead, silent rehearsal of phonologically unfamiliar words might be beneficial as it may not make such differences salient, and thereby, increase reliance on native-language knowledge. Findings from this work serves as an important first step into understanding mnemonic strategies that can potentially lead to better word learning and help create stronger links with long-term memory. Results must be interpreted with caution, however, given that the effects were observed for immediate but not long-term recall.

Blogger: Theresa Pham is a student in the combined SLP MClSc/PhD program, supervised by Dr. Lisa Archibald.

Learning and Overnight Retention in Declarative Memory in Specific Language Impairment

Lukács, Á., Kemény, F., Lum, J. A., & Ullman, M. T. (2017). Learning and overnight retention in declarative memory in specific language impairment. PloS one, 12(1), e0169474.

Memory is divided into a long-term memory system and a working memory system. Research has demonstrated that children with developmental language disorder (DLD; also referred to as specific language impairment) have poor working memory which means they have difficulty holding and manipulating information in mind that they have just received. There has been less research examining the long-term memory system in children with DLD. The long-term memory system has two types of memory; procedural and declarative memory.  Procedural long-term memory is our knowledge of how to do something such as ride a bike or tie our shoes and declarative memory is a type of long-term memory used for recalling facts, knowledge, events, and words.
The present study examined the role of declarative memory in children with DLD. The researchers assessed both immediate learning (10-minute delay) and retention (1-day delay) using nonverbal stimuli (seeing pictures of objects) and verbal stimuli (hearing words). Children who were typically developing and children with DLD were asked to complete a recognition task that was used to assess declarative memory. The recognition task was a judgement task where the participants had to indicate if they had seen or heard the item before. Participants first completed an encoding phase where they were presented with 32 real and 32 novel items. This was completed for both nonverbal and verbal stimuli. They completed the judgement task 10-minutes after the encoding phase and again 1-day after the encoding phase.

The researchers found that for nonverbal stimuli the typically developing children showed no change in accuracy between the 10- minute delay and the 1-day delay but children with DLD were significantly more accurate at the 1-day delay compared to the 10-minute delay. The typically developing children performed significantly better than the children with DLD when tested after the 10-minute delay but there was no difference between groups at the 1-day delay. This result indicates that after some consolidation the children with DLD were more accurately able to identify nonverbal items seen before. For verbal items, typically developing children performed better than children with DLD and they did not find the same trend of better performance in the DLD group at the 1-day delay. This result was not surprising since children with DLD are known to have difficulty with word learning.

These results would suggest that children with DLD have consolidation strengths in declarative memory, specifically for non-verbal items. This finding demonstrates the importance of consolidation and sleep for learning new objects. It would suggest that time for consolidation might be important when determining what a child with DLD has learned.

Blogger: Meghan Vollebregt is a student in the combined SLP MClSc/PhD program working under the supervision of Dr. Lisa Archibald.