Social Influence Module

The social influence model set is the first major addition. These models store and calculate social relationships between an agent and its peers. Each submodel calculates a metric for social influence, each of which is used by the motivation mechanism for attention. This allows agents to pay more attention to agents with a high degree of social influence upon them, an important factor in how memes spread within a society.

All factors contained in the social module are relationships toward other agents. The PMFServ standard relationship model implements social factors for valence and agency. Valence is the like or dislike toward another agent. Agency is the level to which the other person is perceived as human and an actor in the environment. The social identity model is a separate model which keeps track of group affiliations, strength of membership, and roles in groups.

Table 5.3: Theories Implemented in Social Influence Module

Theory Source Implementation

Dual Process Persuasion Petty and Cacioppo(1986) Composite (Partial)

Conformity Asch(1955) Direct

Similarity Platow et al.(2005) Composite

Halo/Valence Kelley(1955) Direct

Authority Milgram (2004) Direct

In-Group Tajfel(1982) Composite

Reference Group Kameda et al.(1997) Composite

Transferability Bandura(1986) Direct (Partial)

The social influence theories used to design the social influence model set are noted in Table 5.3∗. Each of these factors are used as inputs to the attention model, explained in Section 5.2.5. These factors are also used to help mark up an agent’s perception of the environment, by adding activations as a function of social influence factors. The mechanisms for applying these additional activations are applied at the scenario level, as part of the perceptual mark ups. This allows them to be processed using the standard decision making algorithm. Each component of social influence will be discussed briefly to explain its contribution. Dual Process Theories of Persuasion

The dual process persuasion theory has been used as a guideline in the design of event processing but has not been directly instantiated with detailed dynamics of specific dual process models as discussed by Chaiken and Trope (1999).

∗

A credibility component was also designed but was not used during the design process because insufficient data was available to initialize this model.

The dual process theory has been applied to help differentiate between central and peripheral factors, a key aspect of Petty and Cacioppo (1986) Elaboration Likelihood Model (ELM). Within the context of processing an event, central processing evaluates the actions and outcomes involved. This is because an event’s action is activity (signal) that an agent sends into the environment. Aspects of the agents involved may also be considered, but will not be considered in isolation. Peripheral factors within the PMFServ cognitive model are those which depend only on the relationship between the perceiver and the observed agent.

The social components are primarily peripheral factors, with respect to attention and persuasion. Conformity, similarity, valence influence, authority, ingroup membership, and group reference value are peripheral cues used by the agent cognitive model. Purely central cues include novelty and repeated exposures. These cues will be discussed in the section on the attention module (5.2.5). Motivated attention, selective attention, and transferability have peripheral and central components, so these are counted as central processing. While these classifications are not stated at the code level, they provide interesting semantic considerations for how these components contribute to the cognitive model.

Conformity Influence Model

The conformity model has its theoretical roots in the seminal work done by Asch (1955). Later work by Tanford and Penrod (1984) proposed the Social Information Model (SIM), a probabilistic conformity influence function. Using this function, a curve was derived for conformity influence based upon upon the number of conforming agents and the number of dissenting agents. This two- input function was used as the basis for the conformity influence model added to PMFServ. The Tanford and Penrod(1984) analysis produced a curve as stated in Equation 5.1, where S is the number of influence sources and T is the total number of targets (naive agents that are not influence sources).

Conf ormityInf luence(S, T) =e−4∗e −S1.75

T

(5.1) The implemented conformity model uses this equation verbatim. However, the context of its usage is slightly different than that of the original SIM model. While that model assumed a set of confederates, these models assume agents act based upon their own opinions but still exert influence. As such, any set of agents engaged in a particular activity form a group of influence sources (S). The remaining agents involved in other activities are the target group (T).

As such, agents can calculate the conformity influence of any activity in the simulation as a function of the number of agents it sees engaging in the action

versus those who are not engaged in the action. This conformity term is then passed to other models such as attentional salience, to determine how an agent learns and behaves.

Similarity Influence Model

The similarity model calculates a social influence factor based upon how much an agent feels it has in common with another agent. The influence of similarity on attention and influence has been an influential topic in the domains of social psychology and social network analysis (Platow et al., 2005). In a real social environment, this type of influence is quite complex due to the subjectivity and iterative nature of determining who is similar to oneself. Perceptions of similarity are based off of behavior, social cues, and secondhand knowledge.

Normatively, similarity between beliefs helps agents determine who is likely to want to engage in similar behavior, such as common interests. Work using PMFServ has approached this issue, by attempting to build models of others’ beliefs using parameter estimation approaches (Johns,2007). However, this work used primarily normative approaches such as simplex optimization and would not be appropriate for this project, which attempts to descriptively model humans. However, modeling how humans estimate similarity in a descriptively detailed way is a complex issue. Social cues such as clothing, speech, and other commonly studied metrics are too fine grained for the scope of this project.

PMFServ contains a second model for estimating similarity, known as GSP congruence (Silverman et al.,2006). This model assumes that agents accurately perceive the similarity of other agent’s personalities with respect to their own. As noted, the GSP model in PMFServ is a hierarchal set of weighted nodes. In order to calculate GSP congruence, the two agents’ GSP trees are transformed into vectors of normalized linear weights. Each element of these vectors represents specific personality trait. GSP congruence is calculated as a distance between these vectors. The standard GSP congruence function is shown in Equation5.2, where−−−−→WGSP1is the perceiving agent’s GSP vector,

−−−−→

WGSP2is the observed agent’s

GSP vector, andN is the number of elements in −−−−→WGSP1.

GSP Congruence(−−−−→WGSP1, −−−−→ WGSP2) = PN i=1( −−−−→ WGSP1[i]− −−−−→ WGSP2[i])2 PN i=1( −−−−→ WGSP1[i])2+ ( −−−−→ WGSP2[i])2 (5.2)

By allowing agents to detect this factor without noise, the model assumes that the agents generally estimate an accurate perception of similarity. This is done by allowing agents to directly access another agent’s GSP (Goals, Standards, and Preferences) in order to calculate a similarity metric. This model is typically applied where agents are expected to have a priori knowledge about other agent’s personalities, such as agents who have know each other well. Even where agents

are not familiar, it provides a useful first order estimate of the perceived similarity which is appropriate when people can quickly generate accurate perceptions of similarity.

The similarity influence model builds off of the GSP congruence model, using GSP congruence as a similarity term. This model also operates as a wrapper to allow subclassing the similarity influence functionality, as not to make it wholly dependent upon the specific implementation of GSP congruence.

Halo/Valence Influence Model

The valence influence model represents the social influence caused by general like or dislike of another person. This is related to the “halo effect,” such as where an attractive person appears more competent (Kelley, 1955). Experiments such as Hilmert, Kulik, and Christenfeld(2006) have experimentally shown that valence can affect social influence. Since PMFServ already has a model for maintaining valence, the valence influence model consumes and exposes this parameter so that it can be exposed as an influence value. Since valence ranges from [-1,1] in PMFServ and all influence values are fitted into a range of [0,1], a small transform is applied to valence values to rescale and shift it into the appropriate range. Authority Influence Model

The authority influence model represents the additional influence conferred by a position of authority. The effects of authority on behavior have been well documented by Milgram (2004) and Mantell (1971). PMFServ has the ability to represent the authority of agents within the groups which they belong to (Silverman et al., 2006). This value fits within the appropriate range and has the appropriate semantic meaning, so the authority influence model wraps and exposes this authority influence metric so that other models can take this into account.

In-Group Influence Model

The in-group influence model represents the social influence based on belonging to a mutual group or clique (Tajfel,1982). PMFServ has a structure for representing group membership, which allows members to be part of a group. Similarly, groups can be arranged in hierarchies that confer membership into supergroups. The current implementation of in-group influence counts an agent as belonging to the same in-group only if they share the same primary group. This means that while in-group influence is technically a value with a range of [0,1], it actually functions as a boolean value.

Reference Group Influence Model

Reference group influence represents the influence based on an agent belonging to a group against which an agent compares themself, such as a desirable group (Kameda et al., 1997). PMFServ has an analogous factor within its model set that is an agent’s “internal membership” with a group (Silverman et al., 2006). Internal membership measures how much an agent desires to participate and support a group. Since this measure is explored within other papers, it will not be covered in detail here.

Reference group influence uses a variant of PMFServ internal membership that has been scaled to fit into a range of [0,1]. This model can report back the desire to belong in any given agent’s group (if they belong to a group). This approach to reference group influence has a few important dynamics of note. Firstly, the value can cover anywhere in the range of [0,1], unlike in- group influence. This value is also independent of in-group influence, in general. However, the calculation of internal membership bases some of its parameters upon the perceived leader of the group being considered. This leader is either a specifically designated agent, or the agent with the highest authority. In particular, the GSP congruence of the leader is used as a metric similarity with the group as a whole. This means that reference group influence and similarity influence will have some covariance when an agent considers a leader, since the leader’s parameters represent himself and are partially representing his group’s influence.

Transferability Influence Model

Transferability influence refers to the additional influence conferred by an agent who has similar capabilities and does actions that one could imitate. Often, this trait is studied in children at different developmental stages. Children have a preference to attend and imitate those of similar ability level on tasks (Bandura, 1986).

The transferability influence model allows agents to process an observed event and determine if they could do the same action at the current time. This determination is only based upon the agent’s current affordances at the particular moment, not any past or potential affordances. This implementation has the advantage of easily classifying events into those which they could imitate and those that they could not. However, it is conservative since agents will not assess an action as transferable (imitable) if it is not currently available- even if they did that action previously. With that limitation in mind, this implementation still allows the agent to consider important information about their ability to imitate an activity and consider that when processing events.