Two mechanisms in the stimulus suffix effect

The stimulus suffix is a redundant item presented immediately after a stimulus list. Its effect is the selective impairment of recall of the final items in a serially recalled, auditorily presented list of unconnected items. Two experiments indicate that there was no difference between the effects of suffixes .5 and 1.0 sec after the end of a digit list presented at a rate of one digit/sec. This suggests that the effect of the suffix, in this case the vowel sound "ah," is not a simple function of its time of arrival after the final digit, as has been thought. The possibility of more complex factors was supported in a further experiment which showed a slight reduction in the size of the suffix effect by repeating the suffix three times.     

Capturing the suffix: cognitive streaming in immediate serial recall

Adding an irrelevant item to the end of an auditory to-be-remembered list increases error on the last list items appreciably, known as the suffix effect. The phenomenon of auditory capture (e.g., Bregman & Rudnicky, 1975), namely, the tendency for a sequence of similar items to form a stream that at the same time isolates perceptually dissimilar members of the sequence, is exploited to explore the suffix effect. Irrelevant items interleaved between to-be-remembered items are used to capture the suffix with the aim of reducing its impact. Four experiments illustrate how the properties of the irrelevant sequence promote capture. The results are problematic for models of the suffix that involve masking of the last list item; instead, models based on grouping are favored.     

Isolation of items and the stimulus suffix effect

Thirty Ss heard and serially recalled 36 different nine-digit series. The recall cue was a buzzer, the wordzero read in the same voice that read the first seven digits, or the wordzero read in a voice different from the one that read the first seven digits. In half the series, all nine digits were read in the same voice. The final two digits of the remaining series were isolated by having them read in a voice different from the one that read the first seven digits. Zero suffixes disrupted recall of the terminal digits more than the buzzer (the stimulus suffix effect) and had a greater degrading effect when they were in the same voice as the final two digits than when the zero suffixes and the final digits were read in different voices. Isolated digits were more likely to be recalled than nonisolated digits. Results suggest the importance of perceptual analysis in both the stimulus suffix effect and the isolation effect.     

Decay theory of immediate memory: From Brown (1958) to today (2014)

This work takes a historical approach to discussing Brown's (1958) paper, “Some Tests of the Decay Theory of Immediate Memory”. This work was and continues to be extremely influential in the field of forgetting over the short term. Its primary importance is in establishing a theoretical basis to consider a process of fundamental importance: memory decay. Brown (1958) established that time-based explanations of forgetting can account for both memory capacity and forgetting of information over short periods of time. We discuss this view both in the context of the intellectual climate at the time of the paper's publication and in the context of the modern intellectual climate. The overarching theme we observe is that decay is as controversial now as it was in the 1950s and 1960s.     

Channel-capacity, intelligibility and immediate memory

When subjects try to remember lists of digits played to them through pulse-modulated white noise the number of errors they make is greater than would be expected if digitrecognition errors and immediate memory errors were independent (Exp. 1).

A second experiment compared recall of digits in early list positions, when digits in subsequent list positions were presented through noise, and in clear. Digits in early positions were less well remembered when digits in later list positions had to be discriminated through noise.

In a third experiment prose passages were played to subjects who subsequently answered questions about their factual content. Judged by this technique recall of the first half of a prose passage is less accurate if the second half must be heard through noise than if the entire passage is heard through a good fidelity system. These results together are interpreted as demonstrations that increased difficulty of recognition of speech through noise may interfere with other activities, (conveniently termed “rehearsal”) which may be necessary to efficiently retain data in memory.     

Handedness, eye-dominance, and immediate memory

Twenty male university students varying in handedness and eye-dominance recalled conventional and unconventional digits under two conditions: (1) when the same type of digit was projected simultaneously to each eye, and (2) when a different type of digit was projected simultaneously to each eye.

Forty trials were given, each consisting of four pairs of digits with a different numeral projected to each eye. Performance was analysed in terms of percentage recalled correctly and time of onset of each response.

Right eye-dominant groups, particularly a right handed and right eye-dominant group, were superior in both accuracy of recall and speed of response to left eye-dominant groups. Least able in recall were left handed, left eye-dominant subjects. Superiority of right eye-dominant groups was especially marked when a different type of digit was projected to each eye.

In accord with results reported by Broadbent for the ears (1956, 1957), other results suggest it is possible for the eyes to operate simultaneously as independent information sources. However, unlike the case for audition, present subjects did not report all information from one eye before that from the other, but gave it in pairs. It seems that the capacity of the eyes to function independently depended upon eye-dominance and handedness, while serial ordering of responses reflected imposition of an habitual response organization.     

Exploring the suffix effect in serial visuospatial short-term memory

The suffix effect—the loss of recency induced by a redundant end-of-list item—was studied in a visuospatial serial recall task involving the memory for the position of dots on a screen. A visuospatial suffix markedly impaired recall of the last to-be-remembered dot. The impact on recall was roughly of equal magnitude whether the suffix shared attributes with the to-be-remembered dots (Experiment 1) or was visually distinct (Experiments 2 and 3). Although the presence of a tone suffix also impaired serial memory for the last items in the sequence, the impact of a visuospatial suffix was more marked, implying a specific as well as a possible general effect of suffix in the visuospatial domain (Experiment 4). The suffix effect seems not to be a phenomenon confined to verbal material but rather a universal phenomenon possibly related to grouping.     

The role of memory in attenuations of the suffix effect

Various properties attenuate the auditory suffix effect. These properties may improve recall by allowing the suffix to be excluded from the auditory store (or stores) used for immediate ordered recall, or they may improve recall even though the suffix is included in the auditory store. Nine items were presented, with the last item being either a suffix or another item to be recalled. In Experiment 1, the impairment in recall of the previous items produced by presenting a to-be-recalled last item in a different voice was the same as the impairment produced by presenting a suffix in a different voice. The same result was found in Experiment 2 for presenting the last item in a different spatial location and in Experiment 3 for delaying the presentation of the last item. Apparently the attenuating properties improve recall through memorial factors, and not by allowing the suffix to be excluded from the auditory store.     

Expert memory: the interaction of stimulus structure,attention, and expertise

This experiment focuses on the three‐way interaction between domain‐relevant structure, attention to domain‐relevant structure, and expertise in their effect on recall for field‐hockey information. It was predicted that experts' recall would decrease with the amount of domain‐relevant structure, but only when they were able to attend to the structure within the stimuli. Novices' recall was not predicted to vary with these factors. The study used a 3 × 2 × 2 mixed‐design with one between‐subjects factor, field hockey expertise (expert and novice), and two within‐subjects factors, domain‐relevant structure (high, moderate and low) and attention to structure (attending and non‐attending). Twenty‐four experts and 24 novices each listened to six audio‐taped scenarios (1 in each of the 6 structure × attention conditions) describing a sequence of field hockey play and recall was tested. The results demonstrated significant main effects for expertise, structure, and attention, and interactions of (a) structure and expertise, and (b) structure and attention. Importantly, the significant structure, attention, and expertise interaction provided the first direct empirical support for the constraint attunement hypothesis (Vicente and Wang, 1998 ) and for that aspect of the template theory (Gobet and Simon, 1996a , b ). Copyright © 2002 John Wiley & Sons, Ltd.     

Recency, immediate recognition memory, and reaction time

Four classes of possible mechanisms for short-term item recognition are distinguished: (I) pure list-search, (II) direct-access activation (or trace strength) discrimination, (III) mixtures (of I and II), and (IV) response-association. Manipulations of recency, particularly of negative probe items, provide critical tests between them. Two experiments are reported using Sternberg' s 1966 varied-set reaction time paradigm, coupled with procedures intended to minimize rehearsal and control the recency of probes and memory set items. RT and error rate were greater for negative probe items that had recently been presented than for items less recently presented, and this effect increased with positive set size. In contrast, positive RT was, except for the initial item, a decreasing function of recency (= serial position), and there was no additional effect of set size per se. A brief filled delay between list and probe increased positive RT but not the slope of the set size function. These and other findings appear to reject models of Classes I and IV and, while implying some direct discrimination of an item's recency, require modification of the models of Classes II and III. The implications are discussed with respect to the relation between the two versions of Sternberg's paradigm and also in connection with facilitatory “priming” effects in memory.     

Reliability estimates for the immediate and delayed memory tasks

The Immediate and Delayed Memory Tasks are variations of the Continuous Performance Test. While previous research with the tasks has focused on group performance across multiple blocks and sessions, reliability estimates have not been established. We estimated reliability (1) between blocks of a single testing session (N=106), (2) across four sessions within a single testing day (N=20), and (3) across sessions on four consecutive testing days (N=20). Analyses indicated that the primary variable of interest, i.e., commission of errors, showed acceptable reliability within and across testing periods.     

Primacy, recency, and suffix effects in auditory short-term memory for pure tones: evidence from a probe recognition paradigm.

The present study was designed to explore serial position and suffix effects in the short-term retention of nonverbal sounds. In contrast with previous studies of these effects, a probe recognition paradigm was used to minimize the possibility that participants would use a verbal labelling strategy. On each trial, participants heard a memory set consisting of three pure tones, followed five seconds later by a probe tone. Participants were required to indicate whether or not the probe tone had been a member of the memory set. On most trials, a suffix sound was presented 1 second following the third sound in the memory set. Results revealed that tones presented in the first and last positions of the memory set were recognized more accurately than were tones presented in the middle position. Furthermore, recognition of sounds presented in the last position was compromised when the memory set was followed by a postlist suffix of similar pitch, spectral composition, and spatial location.     

Suffix effects and probe modality in probed recall: Implications for readout from sensory memory

The effect of a redundant stimulus suffix was investigated in three experiments using a probed recall task. The probe modality was auditory in the first experiment and visual in the second. In the third experiment, both probe modalities were tested. The presentation rate was varied in all three experiments and was confounded with the delay of the suffix. The suffix was found to have a small and approximately equal effect on the last six serial positions. In contrast to the predictions from Crowder and Morton's (1969) PAS model, presentation rate and suffix delay did not interact with the suffix effect. The results indicate that at least six items can be simultaneously represented in PAS, that there is no appreciable decay of information from PAS during presentation of the last list items, and that readout of PAS information does not occur either during list presentation or between the end of list presentation and the beginning of overt report.     

Laterality of phonological working memory: dependence on type of stimulus,memory load,and sex

Investigations of the laterality of phonological working memory have not always yielded consistent results. The present experiment investigated working memory for letters and numbers in two memory load conditions. In the low load condition, working memory for letters and numbers was similar. However, in the high load condition, males were more accurate at the recall of letters. This effect was not observed with numbers, in which both sexes performed more poorly. Furthermore, we observed consistent RVF advantages for both tasks, although males were more asymmetrical for the recall of letters and females were more asymmetrical for the recall of numbers. This result indicates that laterality of working memory for letters and numbers differs, and these asymmetries depend upon the sex of the participant.