VACACIONES DE LA LEY O VACATIO LEGIS

The experiment was programmed using JavaScript and presented to participants via their internet browser. To widen participation, the experiment was translated into French and delivered in exactly the same manner as that outlined in English below.

3.2.4 Design and Procedure

After reading onscreen instructions, participants started the single study-test block. The study phase consisted of a self-paced 132 trial incidental encoding task.

Intermixed randomly within these 132 trials were three presentations of each of the 24 High Familiarity items, along with a single presentation of each of the 60 Low Familiarity items. For each item presented in the center of the screen, participants responded to the question “Does this image have purple in it?”, presented above the item, with either a “yes” or “no” response (Figure 3.3a). Responses were made using either the keyboard (1 = “yes”; 0 = “no”), if the participant was undertaking the experiment on a computer, or by pressing buttons below the item if they were undertaking the experiment on a touchscreen device (Figure 3.3a). A 0.1 second inter-trial-interval black screen preceded each trial.

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Figure 3.3: Experiment 2 experimental design. Examples of trials within a a) study and b) test phase.

The test phase was presented immediately following the study phase. At test, items were presented in pairs: one questioned item and one concurrent item. Questioned items were either N or LF, but not HF. This was implemented as minimizing

experiment duration is crucial for online studies, and this experiment was designed to investigate familiarity and novelty processing rather than recollection.

Recollection is known to contribute to high confidence old judgements, and as such, while HF items were used as concurrent items, recognition for these was not directly tested. Six test-pair conditions were based on the memory status of the two

concurrently presented items (questioned items are underlined): (i) N-N; (ii) N-LF; (iii) N-HF; (iv) LF-N; (v) LF-LF; (vi) LF-HF (see Table 3.1).

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Table 3.1: The six within-subjects test conditions undertaken by participants.

The test phase consisted of 84 self-paced trials. At test a first item appeared either on the left or right of the screen. After a 0.8 second delay, a second item appeared on the other side of the screen. At the same time as the second item appeared, a red border appeared around one of the items, indicating to the participant that this was the questioned item. Presentation was staggered to encourage participants to pay attention to, and process, the first item presented on screen. The participants then responded by indicating whether the questioned item was “old” or “new” in the same way that “yes” and “no” responses were made in the study phase (Figure 3.3b). Keyboard and button responses were disabled until the second item and red border had been presented onscreen, such that participants could not respond before this. A 0.2 inter-trial black screen preceded each trial.

Primary trials of interest in which the questioned item appeared onscreen second (to allow participants time to attend to and process the concurrent item) occurred for 80% of the trials in each conditions. The remaining 20% of trials were catch trials in which the questioned item was that which appeared onscreen first (Table 3.1). This ensured participants did not simply ignore the first item presented onscreen. Questioned items were presented on the left and right hand side of the screen in a pseudorandom order. Of the 84 items questioned at test, 48 questioned items were N lures and 36 were LF targets. This allowed a 1:1 ratio of new and old item to be

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presented on screen during the test phase, as differing numbers of old and new items can affect bias (Ratcliff & McKoon, 2007). A 0.2 second black inter-trial-interval screen preceded each trial.

3.2.5 Calculations

To investigate the effect of a concurrent item’s mnemonic status on recognition memory, mean adjusted hits (H'), correct rejections (CR'), misses (M') and false alarms (FA'), along with the sensitivity (d') and bias (c) parameters estimated from these (Macmillan & Creelman, 2005), were the measures of principal interest for this experiment. These were calculated for each participant as outlined in Section 2.2.4 (page 46) of the previous chapter.

3.2.6 Data Analysis

Participants’ performance was investigated relative to chance by submitting the parameter estimate of sensitivity (d') to a one-sample t-test, with zero as the value of comparison. Participants’ overall bias (c) was also assessed using a one-sample t- test, with zero as the value of comparison, where c = 0 shows optimal bias.

Following this, to question the effect of the mnemonic status of concurrent items on adjusted hit (H') and correct rejection (CR') rates, each was submitted to a separate one-way repeated measures ANOVA with the mnemonic status of the concurrent item (New - N, Low Familiar - LF, High Familiar - HF) as the within-participant factor. Any significance was further assessed using Bonferroni corrected Pairwise

comparisons.

Measures of sensitivity and bias were also each submitted to a one-way repeated measures ANOVA with the mnemonic status of the concurrent item (N, LF, HF) as the within-participant factor. Any significance was further assessed using Bonferroni corrected Pairwise comparisons.

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For all one-way repeated measures ANOVAs, where the data were found to violate the assumption of sphericity, as denoted by a significant Mauchly’s test,

Greenhouse-Geisser corrections were applied. Where this is the case it is explicitly stated within the reporting of the results.

A a threshold of 0.05 was adopted for all statistical analyses reported.

3.3

Results

The main focus of the present experiment was to investigate the effects of the mnemonic status of concurrent items on recognition memory. Thus, only results pertaining to primary test trials in which the questioned item was second were analysed. Furthermore, due to the nature of an online study where participants can easily concurrently engage in other tasks, mean hit and correct rejection response times (RTs) were calculated for each participant, and trials where RTs were under or above 3 standard deviations from the participant’s mean RT for that response (hit or correct rejection) were excluded from further analyses. A mean of 0.98 trials were excluded per participant (SD = 0.69, rage = 0 - 3). This equated to a total of 262 trials being excluded across all participants (1.2% of all trials), 260 for being above three standard deviations above participant’s mean RT, and 2 for being under.