Does the Type of Transducer Influence Digit Span Test for Assessing Short-term Memory?

INTRODUCTION

Working memory denotes the ability to retain stimuli and allows the temporary storage of relevant information.^1,2 Digit span test is one of short-term memory test to evaluate cognitive status.^3,4 There are two types of digit span test, that is, forward and backward digit span tests which are most widely used test for the short-term working memory (STM).⁵ short-term memory helps the individual to retain, follow, and integrate the stream of auditory information which is considered an important factor contributing to receptive speech development, auditory processing, auditory perception, and other higher cortical functions, such as intelligence, cognition, and attention.^6,7 In forward digit span test, the digits are recalled in the same order, whereas in backward digit span, the digits are recalled in the reverse order.⁴ Traditional digit span testing was influenced by two factors. First, the examiner’s variation in loudness, rate, pitch, emphasis, and clarity of digit, and second, the variation in clarity between different examiners.^8,9 It was also reported that the digit span test is also affected by the rate of presentation between two-digits, duration of digit which is called the administrative error⁴ and hormonal changes¹⁰ Hence, an accurate recorded stimulus should be presented randomly through computer for digit span test⁴ Previous researches also suggested that substantial variability influence the result of auditory digit span test.^7,4 Hence, it may be assumed that forward and backward digit span tests may also be influenced by the use of transducer, that is, headphone and loudspeaker. Hence, it is necessary to study the effect of transducer on auditory digit span test.

METHODS

A total 44 number of participants were included in this study with the age range of 18–25 years (Mean age – 20.9 years, SD – 0.9). Participants in this study had no any otological and medical-related issues, no neurological abnormalities, and no history of using alcohol and steroid. All participants had thresholds of pure tone audiometry within 15 dBHL at octave frequencies from 250 Hz to 8000 Hz as per Goodman’s classification for degree of hearing loss,¹¹ Speech recognition threshold of up to 25 dBHL, and speech identification of monosyllables of at least 88%¹² with “A” type tympanogram^13,14 and normal acoustic reflex threshold ranging from 85 dBSPL to 100 dBSPL at the octave frequencies 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz ipsilateral and contralateral in both ears.¹⁵ Auditory digit span testing was done using APEX 3 software using calibrated headphone (TDH 39) and loudspeaker (ALPS) in soundproof room. The order of transducer presentation and order of forward and backward digit span test were alternated between headphone and loudspeaker to avoid order effect. At least 30 min gap had been given to avoid learning effect to each participant. All testing were done in sound-treated room and consent form was taken from each participant before testing.

RESULTS

The result of the current study shows that there is no significant difference between both the transducers for forward as well as backward digit span tests.

Figure 1 shows the mean and standard deviation of the forward digit span test between headphone and loudspeaker. From Figure 1, it can be seen that there is very less difference in mean and standard deviation between two transducers. A paired sample Z-test shows no significant difference between headphone and loudspeaker in forward digit span test (Z = 3.692, p > 0.05).

The mean and standard deviation of the backward digit span test between headphone and loudspeaker is shown in Figure 2. Figure 2 shows that there is very less difference in the mean and standard deviation between two transducers. A paired sample Z-test also shows no significant difference between headphone and loudspeaker in backward digit span test (Z = 3.712, p > 0.05).

DISCUSSION

The main purpose of the present study was to see the effect of transducers used for auditory working memory test. In the current study, the examiner administrated computer-controlled and randomized presentation of recorded digit (forward and backward) were used to test the auditory working memory or short-term memory. Previous studies also suggested that auditory digit span test is used to test short-term memory and computerized tests of digit span should be used clinically than traditional paper and pencil digit span test.⁴ The examiner administrated computer-controlled digit span test has significantly enhanced the test–retest reliability and precision of this test for assessment.⁴ The mean differences also found between forward and backward digit span scores in free-field condition and forward digit span score was better than backward digit span score test. The same findings were also found in headphone condition. In the previous studies also, it has been reported that the auditory working memory was better for forward digit span test than the backward digit span test¹⁶ In the previous literatures, the computerized-based digit span testing was done using headphone and dearth of studies are available to suggest the use of loudspeaker for auditory digit span test. Previous study also reported that the presentation mode of stimulus may influence the various audiological testing Hence, in the present study, headphone and loudspeaker were used to see the effect of transducer in forward and backward digit span tests which is one of the testing method variables that may influence the test result findings. Thus, the present study provides information regarding the use of either headphone or loudspeaker as benchmark for the selection of transducer during digit span test.

LIMITATIONS OF THE STUDY AND FUTURE DIRECTION

The present study was carried out with a less sample size. Hence, large sample size is essential for better generalization of present research findings. In addition, the result of the study was limited to only adult in age group 18–25 years. Future studies can consider different age group to verify the obtained result of present study.

CONCLUSION

The study found that auditory digit span test was not influenced by types of transducers. The findings of the present study suggest that loudspeaker can be used alternatively for easy and convenient way to test or considering training of short-term memory especially for children and difficult-to-test population clinically and aural rehabilitation. It is also beneficial for clinicians to recognize factors that influence outcomes of digit span test.

REFERENCES

1. Dobbs AR, Rule BG. Adult age differences in working memory. Psychol Aging 1989;4(4):500. DOI: 10.1037/0882-7974.4.4.500.

2. Kaiser J. Dynamics of auditory working memory. Front Psychol 2015;6:613. DOI: 10.3389/fpsyg.2015.00613.

3. Gathercole SE, Hitch GJ, Service E, et al. Phonological short-term memory and new word learning in children. Dev Psychol 1997;33(6):966. DOI: 10.1037/0012-1649.33.6.966.

4. Woods DL, Kishiyama MM, Yund EW, et al. Improving digit span assessment of short-term verbal memory. J Clinical Exp Neuropsychol 2011;33(1):101–111. DOI: 10.1080/13803395.2010.493149.

5. Richardson JT. Measures of short-term memory: A historical review. Cortex 2007;43(5):635–650. DOI: 10.1016/S0010-9452(08)70493-3.

6. Frick RW. Using both an auditory and a visual short-term store to increase digit span. Memory Cogn 1984;12(5):507–514. DOI: 10.3758/BF03198313.

7. Pisoni DD, Geers AE. Working memory in deaf children with cochlear implants: Correlations between digit span and measures of spoken language processing. Annals Otol, Rhinol Laryngol Suppl 2000;185:92. DOI: 10.1177/0003489400109S1240.

8. Reeves C, Schmauder AR, Morris RK. Stress grouping improves performance on an immediate serial list recall task. J Exp Psychol: Learn, Memory, Cogn 2000;26(6):1638. DOI: 10.1037/0278-7393.26.6.1638.

9. Silverman MJ. The effect of paired pitch, rhythm, and speech on working memory as measured by sequential digit recall. J Music Ther 2007;44(4):415–427. DOI: 10.1093/jmt/44.4.415.

10. Sao T, Jain C. Effects of hormonal changes in temporal perception, speech perception in noise and auditory working memory in females. Hearing, Balance Commun 2016;14(2):94–100. DOI: 10.3109/21695717.2016.1155837.

11. Menzel OJ. Clinical efficiency in compensation audiometry. J Speech Hear Disord 1960;25(1):49–54. DOI: 10.1044/jshd.2501.49.

12. American Speech-Language-Hearing Association. Guidelines for acoustic immittance screening of middle ear function. Asha 1979;21(288):563–569.

13. Jerger J. Clinical experience with impedance audiometry. Arch Otolaryngol 1970;92(4):311–324. DOI: 10.1001/archotol.1970.04310040005002.

14. Jerger J, Jerger S, Mauldin L. Studies in impedance audiometry: I. Normal and sensorineural ears. Arch Otolaryngol 1972;96(6):513–523. DOI: 10.1001/archotol.1972.00770090791004.

15. Gelfand SA. Essentials of audiology. New York: Thieme; 1984.

16. Grégoire J, Van der Linden M. Effect of age on forward and backward digit spans. Aging, Neuropsychol, Cogn 1997;4(2):140–149. DOI: 10.1080/13825589708256642.