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On the locus of redundancy effects in a letter-detection task
J G Rueckl1, S Suzuki, S L Yeh
1Department of Psychology, Harvard University, Cambridge, MA 02138.
Insights
The redundancy effect, where target detection is slower for nonredundant strings, also applies to mixed-case letters and digits. This suggests the effect stems from target presence in noninitial positions, not visual properties, impacting response selection.
Area of Science:
- Cognitive Psychology
- Perceptual Psychology
Background:
- Previous research established a "redundancy effect" in visual search, where target detection is slower for nonredundant letter strings (e.g., BNHTW) compared to redundant ones (e.g., BBBBB).
- The underlying mechanisms of this effect, particularly concerning visual properties versus positional information, remained incompletely understood.
Purpose of the Study:
- To investigate whether the redundancy effect extends to mixed-case letter strings and digit strings.
- To differentiate between hypotheses attributing the redundancy effect to visual properties of noninitial elements versus the target's positional information.
Main Methods:
- Participants performed visual search tasks involving nonredundant and redundant strings of mixed-case letters and digits.
- Reaction times for target detection were measured and compared across conditions.
Main Results:
- The redundancy effect was observed for both mixed-case letter strings and digit strings, mirroring findings with uppercase letters.
- The results indicated that the effect is not driven by the visual characteristics of the noninitial letters but by the target's presence in noninitial positions within the string.
Conclusions:
- The redundancy effect is a robust phenomenon applicable to various character types and cases.
- The findings support a model where the redundancy effect arises from processes in response selection or information readout, rather than solely from early visual processing of noninitial elements.
Abstract:
It takes longer to detect a target if it is the initial letter of a nonredundant letter string such as BNHTW than if it is the initial letter of a redundant letter string such as BBBBB (Johnson, 1986b; Johnson & Blum, 1988). The results of the present study reveal that the redundancy effect also occurs for mixed-case letters strings (e.g., BbbBb) and digit strings (e.g., 22222). In addition, these results suggest that the cause of the redundancy effect is not related to the visual properties of the noninitial letters per se but is instead related to the presence of the target in noninitial positions. Together, these results rule out a number of hypotheses about the cause of the redundancy effect and suggest that the locus of this effect is in processes involved in response selection and/or the read-out of information from the perceptual system.