A sense of self allows us to distinguish ourselves from our surroundings. Self-referential processing engages the cortical midline structures of the brain, particularly the medial prefrontal cortex (mPFC) (Kim & Johnson, 2012). Our sense of self can extend to include objects that are considered especially relevant and important; owned-objects fall into this category due to potential frequent contact. Ownership persuades us to perceive objects as more valuable (the endowment effect), and more desirable simply because we happen to own them (mere ownership effect).
There is also memory advantage for information encoded with explicit reference to the self as opposed to those related to another person, known as the self-reference effect (Cunningham, Turk, Macdonald, & Macrae, 2008). Research by Kim and Johnson (2012) gave evidence for mere ownership and self-reference effects. They asked participants to make preference ratings for a series of items, then arbitrarily assigned those items to a Mine basket or an Other basket, matching them on preference level, estimated cost, gender-specificity, and ease of identification.
When asked to rate the items again, participants tend to rank ‘owned’ items higher in preference levels. They also showed greater and faster recall of an object’s source in Mine compared to Other condition, with increased activation in the mPFC during the former. Interestingly, modulation of activity in the mPFC was only apparent for Mine items that were given higher subsequent preference ranks and not for those ranked lower, or for items in the Other condition.
This indicated that only items more strongly engaged with generate self-objects associations and become incorporated into one’s concept of self. Cunningham et al. 2008) contrasted recognition memory for self-object associations formed through ownership with those formed through action and found that ownership significantly improved memory performance regardless of who acted upon the object. Therefore, although produced action have previously been found to affect cognition, ownership has stronger influence. However, Cunningham and colleagues did not consider the social context in cognition; shopping for an intimate other rather than a stranger could yield different results. Feng, Zhao, and Donnay (2013) studied the endowment effect in self-owned items and mother-owned items.
Both ownership conditions triggered activation in the mPFC during the Sell paradigm. Activation was positively correlated with indifference point, and also increased functional integration with the insula and ventral striatum, which process subjective pain and expected gain, respectively. They concluded that the aversion of losing a possession may be greater than the gratification of obtaining it, and this also applied to mother-owned items because the mPFC incorporated the representation of one’s mother into one’s self-perception.
Evidently, the sense of self can extend to include not only possessions but also intimate others and their possessions, and there may be specific brain regions processing these self-relevant stimuli. Our aim is (a) to test whether there is a memory advantage for self-owned objects, replicating the research done by Cunningham et al. (2008) to validate our study; and (b) to test whether such memory advantage also exists for objects owned by a ‘close other,’ in this case, one’s mother.
Participants will complete a shopping task for self-owned and other-owned items, with the ‘other’ being either a stranger or their mother, and then report which items they remembered shopping for, in a subsequent memory test. We will investigate how the independent variables (IV), item ownership and other type, influence the dependent variable (DV), their recognition memory performance. The first hypothesis is that participants in the stranger condition would show greater recognition for self-owned items compared to other-owned items, consistent to previous findings.
The second hypothesis is that participants in the mother condition would perform better at recognising the other-owned items compared to those in the stranger condition. Methods Participants Our participants were University of Queensland students taking the Neuroscience for Psychologists course in the second semester of 2015. They were tested during 19 separate tutorial sessions, each group consisting of up to 26 people and supervised by a tutor. There were 294 participants comprising of 201 females, 92 males and 1 unspecified gender, with an average age of 20. 4 years.
Two hundred and forty-four were right-handed, 37 were left-handed, and 13 were ambidextrous. There were 145 participants assigned to the mother condition and 149 assigned to the stranger condition. Design We used a within-participants design to study the first IV, item ownership; all participants had to shop for self-owned and other-owned items. We used a between-participants design to study the second IV, other type; each participant shopped for either their mother or a stranger.
The DV, recognition memory performance, was measured by corrected hit rate, a proportion value ranging from -1 to 1 (1 is perfect and 0 is guessing), calculated by subtracting the false alarm rate from the hit rate. Stimuli and Procedure Participants were randomly assigned an ‘other type,’ unless they chose not to think about their mother, in which case they would be automatically placed in the stranger condition. The participants then either answered questions about their mother, or were introduced to a stranger named Lee. Shopping task.
A red and a blue shopping bag appeared on either side of the screen, each one belonging to the participant or the other person. The colour and location of the self-owned bag was counterbalanced across participants, and the bags stayed on screen at all times. Participants were instructed to allocate 50 items into each bag by pressing right or left arrow keys using their right hand. The coloured lines above and below each item indicated the appropriate bag. Items appeared alternately in randomised order, for 1500 ms then followed by coloured lines.
Participants had to start moving the item within the next 2000 ms or it would disappear from screen. Once they started moving the item, it would stay on screen until fully inside a bag, then the coloured lines would disappear. There was a 500 ms pause between items. Surprise recognition memory test. The participants were presented with 150 items (100 old and 50 new), one at a time in randomised order. They had to indicate whether or not they recognised each item by pressing ‘O’ if they did and ‘P’ if they did not, within 1500 ms of an item’s appearance.
A blank screen was displayed for 1000 ms between items. The experiment concluded with the participants reporting basic demographic information such as age, gender and handedness. Discussion We replicated the study done by Cunningham et al. (2008) to see whether there was a memory advantage for self-owned and mother-owned items, compared to stranger-owned items. In support of our first hypothesis, participants had significantly higher corrected hit rates for self-owned items compared to stranger-owned items.
We also hypothesised that participants would perform better in recognising mother-owned items compared to stranger-owned items, but found no significant difference in the results to support this prediction. The findings indicate that items can be associated with one’s self and prioritised in cognition through ownership. Despite the limited exposure and lack of agency, ownership affected recognition memory performance, supporting the premise that the mPFC recruits special attentional resources for the encoding and retrieval of self-owned objects in memory.
From an evolutionary perspective, it is important for us to keep track of all the items that we own, even those that are arbitrary (e. g. gifts) or temporary (e. g. work-load). A mother is an extension of one’s self, while mother-owned items are extensions of the mother, so mother-owned items are much further extensions of the self. This may result in them receiving less priority in cognitive processing, especially considering the fact that they appeared concurrently with self-owned items.
Our brain employs selective attention to effectively process particular things at the expense of overlooking less relevant concurrences. Therefore, our results may simply reflect the lack of engagement and distinct encoding for mother-owned items when presented parallel to self-owned items. At best, it demonstrates that within self-relevant processing there exists distinctions based on centrality. The strength of this study is the experimental procedure which standardizes the physical actions involved in a relatable daily experience, shopping.
This allows us to study cognitive functioning in a context while ensuring that the results are solely influenced by ownership. The limitation of this study is the unsuitable design used to test the second hypothesis. We contrasted memory for mother-owned items and stranger-owned items relative to self-owned items, not to each other. To find out whether someone would prioritize mother-owned items over stranger-owned items in memory, we need a condition where both categories are presented concurrently.
Although this study yielded inconclusive results in regards to comparative memory advantage for mother-owned and stranger-owned items, it provides insight on how the self-reference effect applies to self-owned items. Future research can focus more on how the brain processes different levels of self-extension. It would be interesting to examine the role of agency in self-object association, whether neural differences exist for arbitrary transient ownership in contrast to actual self-selected ownership, and how it affects memory performance.?