Bottlenose Dolphins: Theory Of Mind Research Report

Background

Theory of mind refers to the ability to understand another’s mental states including their intentions, desires and beliefs (Apperly, 2012). An important question and a current debate that researchers are trying to discover is the age at which humans begin to develop a theory of mind. It has been suggested that children develop a theory of mind around 4 years of age (Wimmer and Perner, 1983). However, this has been challenged as some researchers argue that the tests used have additional demands such as language, executive function (Onishi an Baillargeon, 2005) and inhibitory control (Carlson and Moses, 2003) thereby not suitable for nonverbal infants. Therefore, they suggest that infants possess a theory of mind which can be shown through modified theory of mind tasks.

Onishi and Baillargeon (2005) investigated whether 15-month-old infants understand false belief. A violation-of-expectation paradigm was used, and infants were presented with a toy watermelon slice in-between a yellow and a green box. They first underwent three familiarisation trials whereby the actor opened the back doors of the apparatus and played with the toy before hiding it inside the green box for the first trial. In the second and third trials, the actor would then look for the toy in the green box they hid it in. A curtain was used to separate out the trials. The infants then received a belief-induced trial which consisted of four variations: two true-belief (TB) and two false-belief (FB) in order to induce a true or a false belief of where the toy is for the actor.

For the TB-green condition, the top two doors of the apparatus were open enabling the actor to see. Once the actor hid the toy in the green box, the yellow box moved around but there was no change in location of the toy. In the TB-yellow condition, the infant and actor saw the toy being moved from the green to the yellow box. In the FB-green condition, the back-wall doors remained closed therefore, the infant saw the toy move from the green to the yellow box, but the actor did not. In the FB-yellow condition, the actor saw the toy move from the green to the yellow box, the back doors then shut, and the toy moved back to the green box. The infant saw the second movement and knows the toys true location, but the actor does not. The infants then underwent a single test trial whereby the actor opened the apparatus doors and reached into either the green box or the yellow box. Infants’ looking time was measured to test for theory of mind. The infants looked reliably longer in the conditions where the actor looked for the toy that was inconsistent with the actor’s belief about the toy’s location, suggesting they have a theory of mind.

This study is particularly good for testing theory of mind as it enables researchers to investigate it with regards to nonverbal infants. Furthermore, as stated within the study, it is good as it has potential implications for animal cognition therefore, it can be readily adapted to other nonverbal species. (need another advantage?) However, a limitation of this study is that, even though the trials seem easy to follow for infants, the belief-induced trials included several sources of perceptual variation therefore, there is a lot for the infants to take in and keep track of (Sirois and Jackson, 2007).

Proposed research

Onishi and Baillargeon’s (2005) experiment will be adapted to investigate if dolphins have a theory of mind. Bottlenose dolphins are considered to be intelligent (Kuczaj, Gory and Xitco, 2009) and their cognition is suggested to be at a level typical to humans and great apes (Marino, 2004). False belief tasks have suggested a trend towards dolphins having a theory of mind (Tschudin et al., 1999 as cited in Hurley and Nudds, 2006) however, this research will contribute to the current literature through the use of a violation of expectation paradigm using looking time instead. The task in large will remain the same however, some adaptations will be used to make it suitable to carry out with dolphins.

Method

Participants

6 captive bottlenose dolphins will be used, with an equal number of males and females. A within-subject design will be deployed as each dolphin will all undergo all trials.

Materials

The yellow and green boxes used in Onishi and Baillargeon’s (2005) task will be replaced with one smaller bucket (14 litre) and one larger bucket (30 litre) with lids that are visually distinguishable. This is because dolphins have limited colour vision (Griebel and Schmid 2002) but similar visual world to humans (Tomonaga, Uwano and Saito, 2014). The watermelon toy will be replaced with a single large cod, in attempt to maintain their interest, as it is part of their diet (Santos et al., 2001). The curtain will be replaced with a black fabric screen for practicality reasons and will be used to separate out the trials.

Procedure

The dolphin will be presented with a single cod fish in-between two visually distinguishable buckets by the poolside. They will first undergo three familiarisation trials which is the same amount that was administered in the original study. In the first trial, the experimenter picks up the fish, observes it and then puts the cod in the smaller bucket. For the second and third trial the experimenter searches for the fish in the smaller bucket.

Next, they will receive a belief-induced trial similar to that of the original study with two TB-trials and two FB-trials. In the TB-small bucket condition both the experimenter and the dolphin watched the larger bucket move half the distance to the smaller bucket and back into its original position; there was no change in location of the fish. In the TB-large bucket condition, the experimenter and the dolphin watched the fish move from the smaller to the larger bucket. In the FB-small bucket condition, the experimenter turns around and only the dolphin sees the fish move from the smaller bucket to the larger bucket. In the FB-large bucket condition, the experimenter and the dolphin watched the fish move from the smaller to the larger bucket. The experimenter then turns around for 5 seconds and only the dolphin sees the fish move back into the smaller bucket. Dolphins then received a test trial whereby the experimenter either reached into the smaller or the larger bucket.

The dolphins looking time will be recorded for each trial. It has been shown in previous research that we are able to look at the duration of a dolphin’s eye gaze to determine their responses to stimuli (Thieltges et al., 2011).

Predicted results

This study could yield various different results. Firstly, the dolphins could show significant results in both the true-belief and false-belief conditions. Therefore, these results could replicate Onishi and Baillargeon’s findings in infants for dolphins thereby showing dolphins look longer in the conditions where their expectation of where the experimenter searches for the fish is violated and does not match the experimenter’s belief of the fish’s location. This could indicate that they understand that the experimenter has a false belief about where the fish is therefore suggesting they have some implicit form of theory of mind (Onishi and Baillargeon, 2005).

On the other hand, a null result could be obtained whereby the dolphin displays no significant difference in looking time for both the true-belief and false-belief tasks. In this case, the dolphin would follow the actions of the experimenter but would not look reliably longer in the trials which are supposed to violate their expectations therefore, showing no evidence of theory of mind. Nevertheless, it is unlikely that we will obtain these results as previous literature has suggested a trend towards dolphins possessing a theory of mind (Tschudin et al. (1999) as cited in Hurley and Nudds, 2006).

Furthermore, dolphins could show a significance in the true-belief trials but not a significance in the false-belief trials. Similar results were shown in Tschudin et al. (1999) who used false belief task to investigate if dolphins have theory of mind. They showed that dolphins have the ability to pass true-belief trials and that they indicate a trend towards being successful in false-belief trials. There was no significance for passing the false-belief trial however, a near significance was shown (as cited in Hurley and Nudds, 2006). However, a methodological issue that arose from their study which they stated future research could improve on is learning as they conducted a pilot study with the same dolphins beforehand. Nevertheless, this study aims to improve their problems and add to the literature as practice trials and a pilot study will not be administered making our results not suspectable to learning and more valid.

My research intends to further investigate and add to the results produced by Tschudin et al. (1999). I expect that dolphins will be able to successfully pass both the true-belief and false-belief trials and look reliably longer in situations where their expectation is violated by the experimenter’s searching actions. By adapting the study by Onishi and Baillargeon (2005) to make it suitable for dolphins and tackling the learning problem in Tschudin et al.’s (1999) study, we will be able to gain a deeper understanding of whether dolphins have a theory of mind.