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The present study concerns memory conjunction errors made to face stimuli. How are the memory conjunction errors made to face stimuli? It is actually very easy to obtain this type of cognitive error. Facial features are simply recombined from series of previously presented faces. When this method is used, participants have high false-alarm rates for the conjunction faces (Reinitz, Morrissey, & Demb, 1994). Bartlett and Searcy (1998) found similar effects for face stimuli in the form of photographs.
There is much debate as to why memory conjunction errors occur. Two major interpretations currently exist: 1) familiarity explanations and 2) separate experience of stimuli. Those in favor of familiarity explanations claim that participants have memory conjunction errors because parts of the previously presented stimuli seem familiar. The familiarity they have for aspects of the stimuli would lead to an old response to recombined stimuli (Jones & Jacoby, 2001; Jones, Jacoby, & Gellis,2001; Rubin, Van Petten, Glisky, & Newberg, 1999). However, Reinitz proposes a different explanation. According the Reinitz, memory conjunction errors occur because configural information is lost and people end up miscombining features.
Another important issue addressed in the current
study is the effect of proximity. Does the distance between items in a
study list relate to participants being willing to accept distractors constructed
from their parts on a subsequent recognition test? In other words, does
the distance between this stimuli and
this stimuli have some sort
of effect upon how participants later accept similar distractors in later
tests (e.g. ). Various results
for the question of distance have been obtained. For instance, Bartlett
and Searcy (1998) found that faces that were constructed using parts of
other faces were equally likely to be called "old" as conjunction stimuli
constructed from parts of adjacent faces. Thus, proximity had no effect
because all faces were equally familiar. Contrary to the findings of Bartlett
and Searcy (1998), Hannigan
and Reinitz (2000) found "robust" proximity effects. Four explanations
are given as to why proximity effects are not consistently obtained: 1)
nature of stimuli (i.e. identikit faces may produce greater proximity effects
than other types of stimuli) 2) stimuli grouping stim. needs to be grouped
in order to find proximity effects 3) need simultaneity 4) how attention
is distributed to stimuli.
The present study was designed to determine which of the previously mentioned possibilities are true, why they occur, and under what conditions. Four experiments were conducted. All participants studied idendikit faces and took a recognition test that included old and conjoined stimuli. Participants also grouped faces into pairs in different ways in order to further investigate proximity effects. Pairs of faces were presented simultaneously in Experiments 1 and 3; with-in pairs faces were presented sequentially in Experiments 2 and 3. There were long intervals separating the faces. Two members of a pair were presented in an alternating sequence in Experiment 4.
Experiment 1
PURPOSE: To determine if Hannigan & Reinitz's (2000) finding for proximity effect exists for conjunction errors when faces are simultaneously presented.
Method
Participants. One-hundred and eight undergraduates from Boston University participated in part of a introductory psychology course requirement. They were tested in 36 groups. Each group consisted of 3 participants.
Stimulus and apparatus. Faces were line drawings. Each had 2 types of features: eye-nose and hair-mouth. Features were randomly paired together. 144 faces were produced. Ear and face shape were held constant. The faces were presented on Kodak slide projectors.
Design and Procedure. The study phase had 6 trails consisting of 2 faces that were shown simultaneously. Faces appeared at different fixation points one face above and one face below fixation points (they were separated by 1 degree). Each of the face pairs (6) remained on the screen for 16s. A 10s interstimulus interval separated the pairs. Participants were cued when another face was to appear (a beep sounded 300ms prior to stim. onset). After taking a 15-min vocabulary test filler task, participants took an old/new recognition test that had 8 faces presented at once. The following 2 types of faces appeared in each of the 4 test conditions: Old faces study phase, simultaneous-conjunction faces, near-conjunction faces, and far-conjunction faces. Participants proceeded to take an "old"/ "new" recognition test for the faces (chose if faces were identical or not).
Results
Figure 1 shows evidence for a strong proximity effect. Participants had the greatest amount of false alarms to Simultaneous-conjunction faces. False alarms decreased as the distance between the "parent faces" on the study list increased. Thus, Hannigan and Reinitz (2000) replicated their proximity effect results. Familiarity interpretations do not explain the proximity effect obtained. If familiarity was the only process at work, then no proximity effects would be found.
Experiment 2
PURPOSE: To test proximity effects for sequentially presented faces rather than simultaneously presented faces. Pairs were determined by temporal proximity rather than simultaneity.
MAJOR DIFFERENCE: Faces within each pair were presented sequentially instead of simultaneously.
PREDICTION: More with-pair than between-pair conjunction errors in Experiment 2. No proximity effects should be found if simultaneity is the "crucial factor."
Method
Subjects. 108 Boston University undergraduates participated in order to fulfill course credit requirements for their introductory psychology courses. They were tested in groups indentical to Exp. 1 (36 grps w/ 3 partic.s).
Stimulus and apparatus. Stimuli and apparatus were no different from Experiment 1.
Design and Procedure. The only difference from Exp. 1 was that faces were presented sequentially rather than simultaneously. Study faces were presented for 8s and separated by 500 ms blank interval. The first face was separated from the last face by 10 s blank interval. The same study-test stimuli were used. Temporal distances were held constant, except for the Far-conjunction condition (faces were separated by 36.5 s).
Results
There was no evidence found for proximity effects. Proportion of "old" responses did not differ between Experiment 1 and Experiment 2. There was a significant experiment by test condition interaction. The pattern of the results suggests the proximity effects occur for simultaneously presented stimuli and not sequentially presented stimuli. Furthermore, familiarity interpretations better explain the sequential presentation of stimuli.
Experiment 3
PURPOSE: Further investigate the role of sequential and simultaneous presentation. However, new stimuli in the test was introduced in Exp. 3
Method
Subjects. 120 Boston University undergraduates participated in the experiment in order to obtain credit for an introductory psychology course. There were 40 three- subject groups. 20 of the groups were tested with a sequential presentation, the remaining 20 were tested with a simultaneous presentation.
Stimulus and apparatus. The same stimuli and appartatus used in Exp. 1-2 was used in Exp. 3.
Design and Procedure. A similar design (as Exp. 1) was used for participants who received simultaneous presentation of faces; as was the design for those who saw sequential faces (Exp. 2). Changes were made to the test in order to incorporate new stimuli. In the study phase, 10 faces were presented across 5 face pairs. The number of study faces was reduced (for the new items needed for the test), thus eliminating the Near-conjunction test condition. Participants received: 2 Old (faces), 2 Within-conjunction, 2 Far-Conjunction, and 2 New stimuli. False alarms for Far-conjunction and Within-conjunction stimuli were compared.
Results
Overall performance in the 2 study conditions did not differ. There was a significant study condition by test interaction. There was no evidence of a proximity effect for sequentially presented stimuli. The new faces seen on the test were considered "old" less often than for conjunction faces.
Experiment 4
PURPOSE: To determine if attention switching rather than simultaneity causes proximity effects.
Method
Subjects. 148 Boston University undergraduates participated in order to obtain credit for their introductory psychology class. There were run in 16, 3 participant groups 8 received alternating stim. presentation, 8 received non-alternating presentations.
Stimulus and apparatus. The same stimuli and apparatus was used.
Design and Procedure. Test conditions and stimuli orders used in Experiment 3 were used in this experiment. Face presentation lasted for 4s and was separated by a 500ms blank interval. Faces alternated back and forth in the alternating condtition. In the non-alternating condition, the first face was presented consecutively. It was followed by 2 consecutive presentations of the second face in the pair. Presentation times and intervals were similar to those in Exp. 1-3.
Results
The results obtained in the alternating condition were very similar to those obtained for the simultaneous condition. The results obtained in the non-alternating condition were similar to those obtained for the sequential condition. Thus, simultaneous presentation is not needed for the occurrence of proximity effects. The results are due to attention switching between simultaneously presented items.
Relative distance between face (parent) pairs greatly influences the likelihood that participants will claim to have seen a conjunction face. (Exp 1-3 demonstrated this) False alarms were consistently made more for simultaneous presentation conditions than for "Far" presentation conditions. Obviously, there seems to be a great importance in simultaneous presentation. Experiments 2-3 could not find proximity effects when using sequential presentation. Experiment 4 could actually be an indirect way of exposing participants to simultaneous presentation. Switching ones attention back and forth between study items may actually simulate simultaneity.
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