Recall ladder · what the list keeps
Suffix Effect
The drop in recall for the last items in an auditory list when an extra, irrelevant sound or word is appended at the end; a meaningless trailing addition can wipe out the usual recency advantage.
How the trace forms
The suffix effect is explained by the Precategorical Acoustic Storage (PAS) model: auditory input is briefly held in a sensory store preserving pre-categorical acoustic properties. The most recent items in this store provide the recency advantage in auditory lists. A subsequent speech-like suffix overwrites or displaces the lingering acoustic traces of the terminal list items before they can be transferred to a more durable code. The interference is modality-specific and depends on perceptual similarity between suffix and list items at the acoustic level, not at the semantic level.
Competing account — Later work (e.g., Neath & Surprenant 2003; Ayres et al. 1979) showed that semantic and categorical variables can also modulate the suffix effect under some conditions, suggesting that PAS alone cannot fully account for the phenomenon and that post-categorical processes also contribute.
Trials, in order of recall strength
The suffix produced large decrements on the last one to two serial positions, while the prefix produced a non-selective overall decrement; this dissociation supported the existence of a separate precategorical acoustic store.
The suffix effect was insensitive to semantic variables (meaning, frequency, emotionality) but sensitive to acoustic variables (spatial location, timbre, pitch, voice similarity), confirming the precategorical nature of PAS. The suffix must occur within about 1-2 seconds of the last item to be effective.
Retention — robust. The suffix effect has been replicated hundreds of times across laboratories, with consistent findings on the selectivity for terminal positions, the role of acoustic similarity, the ~1-2 second temporal window, and the insensitivity to semantic content. The effect is considered a cornerstone of evidence for echoic memory.
Recalled in the field
everyday cognition · ongoing
Telephone number recall interference
When someone recites a phone number and then immediately says an unrelated word like 'okay' or 'got it,' the listener often loses the final digits—an everyday instance of the suffix effect disrupting the recency advantage in auditory short-term memory.
aviation · ongoing
Aviation and emergency communication protocols
In aviation and emergency services, critical instructions are often followed by confirmation prompts or 'end of message' markers; the suffix effect predicts that these trailing utterances can impair recall of the final instruction, leading to standardized protocols that delay non-essential speech.
To strengthen the trace
Insert a brief pause (2+ seconds) between the list and any trailing utterance to allow the acoustic trace to be transferred to a more durable code; use visual presentation for the last item if possible.
Crowder (1971) showed that delaying the suffix by about 2 seconds eliminates the effect, as the PAS information has been secured by then; Morton (1976) confirmed that absolute timing and rhythm relative to list items both matter.
Catch it in the act
When someone adds an unrelated spoken word or sound immediately after a list you are trying to remember, and you suddenly lose the last item; when 'end of message' tags interfere with recall of the final instruction.
Adjacent in memory
- Modality EffectparentThe suffix effect is a key piece of evidence for the modality effect—better recency for auditory than visual lists; the suffix eliminates this advantage by disrupting the precategorical acoustic store.
- Echoic Memorymechanistically-linkedEchoic memory is the broader concept of brief auditory sensory persistence; PAS is a specific theoretical model of that store, and the suffix effect is its primary empirical marker.