FREE ESSAY ON SHORT TIME RECALL AS A FUNCTION OF TYPE OF STIMULUS AND LENGTH OF DELAY INTERVAL

SHORT TIME RECALL AS A FUNCTION OF TYPE OF STIMULUS AND LENGTH OF DELAY INTERVAL

Abstract
We were interested in examining patterns of short-term information recall. We used the
Brown-Peterson distractor technique to investigate the effects of stimuli type and delay
interval on recall for 17 Ss. Each S was tested under 4 conditions, combined of word
triads or nonsense syllables triads, with a short (10-sec) or long (45-Sec) delay
interval. S read aloud the visually presented stimulus items, and aurally recalled them
after the delay interval, in which S was engaged in counting backwards in threes from a
presented 3-digit number. Measures were taken only for recall proportion. Results suggest
a significant difference in recall between words and nonsense syllables, with words
significantly better recalled. For the delay interval, results show no significant
effect, and thus differ from those obtained in previous research. This discrepancy is
discussed in terms of technical differences in procedure. No other effect or interaction
approached significance. 
Short-term Recall As a function of
Type of Stimulus and Length of Delay Interval
Short-term memory (STM) has been vastly studied and tested. One of the popular testing
methods for STM has been the short-term recall, in which S is shortly presented with a
single or multiple items, later to be recalled. Various researchers have focused their
studies on different aspects, while attempting to identify those factors that most
strongly influence short-term recall. A short-term memory model based upon a limited
capacity to process information suggests that the recall of verbal material can be
effected by the activity which consumes the retention interval, referred to as the
interpolated activity. 
Diverse studies examine the significance of elements involved in the interpolated task.
In general, researchers have attempted to prevent Ss from rehearsing, i.e., processing
exposed stimuli by keeping the material within the short-term store through the use of
rehearsal-preventing interpolated tasks. The most famous of these has been suggested in
the Brown-Peterson technique (Peterson & Peterson, 1959) in the form of backwards
counting. In the original Peterson studies (1959), Ss attempted to retain aurally
presented consonants trigrams while counting backwards by three or four from a
three-digit number. This interpolated activity was continued for some predetermined
retention interval, immediately after which Ss were asked to recall the originally
presented consonants. Using this technique, the Petersons demonstrated a very rapid
decline in recall. The probability of recall decreased exponentially with duration of
interpolated activity. 
Murdock (1960) investigated the effect of the stimulus type and the effect of varying the
rate of interpolated activity. Similarly to the Petersons (1959) he found that in all
cases forgetting, whether measured by accuracy or latency, increased with the duration of
the interpolated activity. In addition, Murdock suggested little difference between the
retention of three consonants and three words; consonant syllables and word triads were
equally well recalled.
Murdock (Tell, 1971) has shown that short-term recall is effected by whether the
presentation is visual or auditory. According to Neisser (Tell, 1971) there is an
auditory-storage system which results from auditory input and can function as a source of
information in short-term recall. This temporary storage system is referred to as echoic
memory. "Echoic memory is passive, continuous, composed of sounds, and decays rapidly"
(Tell, p. 150). 
However, auditory input may also function as auditory noise. Voiced recall, vocalized
irrelevant interpolated activity, or certain types of presentation conditions can mask,
erase, or overwrite information available in the echoic memory store. This assumption is
especially important when considering the interpolated activity. Tell (1971) suggested
that a verbal interpolated task, in addition to its role as a rehearsal-prevention
activity, would also produce auditory feedback, which masks information from echoic
memory. 
Tell and Ferguson (1974) further explored this issue of vocalization by examining the
influences of active and passive vocalization on short-term recall. As distinguished by
Crowder (Tell & Ferguson, 1974), active vocalization refers to presentation conditions
where the to-be-remembered stimulus items are voiced aloud by S as they are visually
presented. Under passive vocalization conditions, S listens to E read each stimulus item
as it is visually presented. Tell & Ferguson suggested that active and passive
vocalization differ mainly at the longer retention intervals, with recall much higher
under the passive vocalization condition. This supported the idea that active
vocalization could interfere with effective rehearsal or encoding strategies.
Another variable manipulated in search of significant effect on recall is whether
interpolated tasks were rewarded or not. Soucar, Walk, and Covert (1971) suggested that
retention of syllables is reduced under rewarded conditions. However, productivity and
accuracy of the actual interpolated tasks was unchanged by reward. 
The present experiment is designed to examine short-term recall as a function of stimulus
type and length of delay interval. We hypothesize that both variables will be found to be
significant. Specifically, we predict that: 1) recall proportion will be higher for words
in compare to nonsense syllables; 2) recall proportion will decrease with the increase of
delay intervals. 
Method
Participants
Seventeen Hunter undergraduate psychology students served as Ss; twelve were female.
Their age range was 18-32. They were demanded to participate in the experiment as part of
their Experimental Psychology course requirement. 
Apparatus The group of participants was assigned to pairs, who conducted the experiment
in small cubicles, so that each pair worked independently of the other pairs. However,
cubicles were not soundproof. Each of the participants served both as S and as E, in
alternation with his/her partner. Two sets of stimuli were presented: nonsense syllables
and words. The class of participants constructed both sets of stimuli. Each E
individually selected twenty-four nonsense syllables and another twenty-four words out of
two separated class-constructed lists. A nonsense syllable was defined as a vowel
surrounded by two consonants, and was selected in such a way as to minimize association
value and avoid acronyms or similarity to any other selected syllables. The words were
3-5 letters long, mostly nouns, and withdrawn from different categories. 
The stimuli were presented on white index cards; each 12.5 X 7.5 cm in size. Each set of
stimuli (words or nonsense syllables) constituted of eight cards. Each stimulus card had
either three nonsense syllables or three words hand written by pen (black or blue), and
located at the center of the card. Size of letters was not precisely controlled, but was
considered appropriate if enabled the S to see it from about two feet away from card. On
the opposite side of the stimulus card was a randomly selected three-digit number,
similarly written and located. Either standard hand watches or digital stopwatches
measured 45 or 10-sec delay intervals.
Procedure 
All sixteen subjects received a 16-trial sequence, involving the presentation of 16 word
or nonsense syllables triads. Each trial consisted of a short visual presentation of the
stimuli, manually performed by E, who set opposite to S. The active vocalization
condition required Ss to read the triads aloud while they were shown. Using the
Brown-Peterson distracter technique (Peterson & Peterson, 1959), Ss attempted to retain
item triads while performing an interpolated task. The interpolated task involved
counting backwards in threes from a presented three-digit numeral. Two lengths of
interval delays were used: 10 or 45 sec. Once the interval delay was over, S would
immediately stop interpolated activity, and orally recall each item, regardless of its
order of position within the triad. E recorded retention scores, which ranged from 0 to
3, with 1 point given for each correctly recalled item. Performance on the interpolated
activity was not recorded. Order of stimuli presentations were constructed in such a way
that no type of stimulus followed itself. Stimuli were presented in the following order:
1) four words-short interval; 2) four nonsense syllables - long delay; 3) four words -
long delay; 4) four nonsense syllables - short delay.
Results
The data of each S were scored in terms of the correct number of items recalled,
regardless of the items' positions within the triad. An overall analysis of variance was
performed on the recall scores. Since one group of Ss was tested under the entire four
conditions (repeated measures), a within-subjects ANOVA was computed for a two-factor
design. Stimuli type served as factor A, while delay interval served as factor B. The
only significant effect found was the type of stimulus presented. As seen in figure 1,
recall was significantly better for words than for nonsense syllables under both
retention intervals {F (1,16)=30.96, P* .05}. Tests of simple main effects for type of
stimuli again showed recall of words (9.3) superior to nonsense syllables (7.02). No
significant difference was found in main effects for length of retention interval; recall
did not decline with the increase in delay interval {F (1,16)=0.005, P* .05}. No
significant interaction (one that would indicate differences not explainable by main
effects) was found between factors A & B, i.e., between stimulus type and retention
interval {F (1,16)=0.76, P*.05}. In summary, only type of stimuli was found to have a
significant effect on recall performance, with a superiority of words over nonsense
syllables.
Discussion
The above-described results lend support to our hypothesis that words are better recalled
than nonsense syllables. As predicted, this effect of type of stimuli was found to be
significant. However, for the effect of length of delay interval, our results
significantly differ from those obtained by previous studies. Peterson & Peterson (1959),
Murdock (1960), and Tell (1971) have all shown a decrease in the proportion of recalled
items as a function of increased retention intervals. In all of these cases, forgetting
increased with the duration of the interpolated activity. Our results suggested no
significance to the delay interval effect. This discrepancy might be explained in terms
of technical differences in procedures. 
Bibliography
References
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