The time-varying nature of decision information can have a specific impact on the psychology of decision-makers. In this section, a dynamic fuzzy decision-making method based on the cumulative prospect theory is proposed.
3.1. Problem Description
The multi-attribute decision-making problem represented by interval triangular fuzzy soft sets is considered. Let represent the set of alternatives, and represent the set of evaluation index parameters. represents the weight vector of evaluation index parameters, represents the time sets of time series T, represents the time weight vector, and meets .
and represent the set of benefit type attributes and cost type attributes, respectively, and . For the evaluation index , the decision maker gives the corresponding interval triangular fuzzy number of scheme at the time of , as . Then, we can obtain the soft set matrix: .
In order to eliminate the difference in decision making caused by dimensions, the cost
and benefit
data types are treated as follows:
The normalized fuzzy soft matrix can be obtained from Equation (10): , .
The problem of dynamic decision making to be solved in this paper is as follows: how to make dynamic decisions obtain the ranking and selection of alternatives according to the interval triangular fuzzy decision-making soft matrix, considering the evolution of psychological expected value, reference dependence, and other behavior problems of decision makers at different time nodes.
3.3. Reference Point Setting Considering the Evolution of Decision Makers’ Expected Value
The decision makers make dynamic decisions at different time nodes according to the current information, which is a process of continuous updating and adjustment of decisions. At the same time, at different decision-making times, the decision makers’ attitudes are different for the two situations that exceed or are lower than the expected value, that is, “gain” and “loss”. Considering the decision makers’ psychological behavior under uncertain or incomplete information, the dynamic psychological expectation value of the decision maker for each scheme at each decision-making moment is introduced as a reference point, the response function of the decision maker to the income loss is given, and then the prospect value of each scheme is obtained as the basis of the optimal decision-making result.
The soft set represents the decision information by analyzing the evaluated object from the perspective of parameters. In this process, the decision maker will naturally produce horizontal and vertical comparisons for different time and different evaluation objects. Therefore, this paper proposes a threshold reference point set: the reference points in each stage are based on the information obtained in the previous stage. The decision maker’s expectation value not only considers the evaluation values of all schemes in the current evaluation stage, it will also generate the expected threshold for the current stage of the scheme according to the development and connection of the initial stage of the self-evaluation of the scheme.
Let
denote the dynamic psychological expected threshold–reference point set generated by the decision maker at each stage of the evaluation index
, where
denotes the threshold–reference point for the evaluation index
scheme
at the time
. The calculation formula of the reference point is:
where
is the adjustment coefficient of positive and negative ideal points. When
, the best value of the scheme since the evaluation period and the current stage of each scheme is selected as the reference point. When
, the worst value of the scheme since the initial stage of the evaluation period and the current stage of each scheme is selected as the reference point.
The threshold reference point set for parameter set
A is thus obtained:
3.4. Determination of Dynamic Decision Scheme
Interval triangular fuzzy soft sets of time series are the unity of interval triangular fuzzy soft sets sorted by time. Under fixed
,
. At the same time, reference [
14] points out that each fuzzy soft set can be expressed as a corresponding fuzzy soft matrix, so the decision-making problem on interval triangular fuzzy soft set can be transformed into an aggregation problem of the interval triangular fuzzy soft matrix, and the optimal dynamic decision-making scheme can be determined by this method.
Suppose that at time
, the decision maker obtains the psychological expectation
according to the current situation and the development trend of the situation. Suppose that the “profit and loss value” of the evaluation index
for
is
. From Definitions 1, 3, 4, and Theorem 1, it can be obtained that the profit and loss value of the evaluation index
for
at time
is:
can be used to measure the psychological benefit and loss utility of decision makers for the expected value. When
, it means that at time
, scheme
has a positive “gain” in index
relative to reference point
. When
, it means that under the time
, the index
of scheme
has a negative “loss” relative to the reference point
. The fuzzy utility value matrix
is obtained through the
value. According to Definition 6 and cumulative prospect theory [
31], the expressions of value functions
and
are obtained:
where
and
represent the fuzzy utility value of scheme
when it obtains positive “gain” and negative “loss” relative to the psychological expectation value
under index
at time
, respectively.
represent the decision maker’s psychological perception sensitivity to profit and loss, where
. The greater the value of
, the more the decision-maker tends to risk preference, and the lower the sensitivity to loss.
is a positive number greater than 0, indicating the degree of decision makers’ avoidance of loss itself. The greater the value of
, the greater the loss aversion [
31].
From Equations (15) and (16), it can be seen that the psychological utility value
,
is limited to 0, and the value of
is arranged:
. Let
denote the psychological utility value at position
. When
, then
. When
, then
. Note that
is the psychological utility value of
at the evaluation time, and the time probability corresponding to
is
. The weight function is used to convert the time probability into weight, so as to evaluate the effectiveness of the aggregation probability of decision samples. According to the cumulative prospect theory [
32], the corresponding weight coefficients formula of
and
is:
The value of parameters in Equations (14)–(19) refers to references [
21] and [
31], and it is appropriate to set
,
,
, and
. Expression of the psychological utility prospect value
for scheme
at time
is:
Here,
and
represent the positive “gain” psychological utility prospect value and the negative “loss” psychological utility prospect value of scheme
with respect to decision makers’ psychological expectations
under index
. The cumulative prospect value
is obtained by combining these positive and negative psychological utility prospect values:
On this basis, the final comprehensive cumulative prospect value of each scheme is aggregated based on the weights of each evaluation indicator
:
In order to determine the weight of evaluation indicators
, the utility prospect values of each evaluation data are first normalized:
Using the entropy weight method based on the value function to obtain the weights of each evaluation indicator,
Here, , and .
Finally, the optimal selection of alternative decision-making solutions is achieved by using the comprehensive cumulative prospect value vector .
The specific steps for dynamic decision-making considering the psychological behavior of decision-makers are as follows:
Step 1: According to Equation (11), calculate the time weight vector .
Step 2: According to Equation (11), calculate the threshold reference point set for the decision maker’s psychological expectations .
Step 3: According to Equations (12) and (14), calculate the psychological utility ‘benefit loss value and fuzzy utility value matrix generated by each evaluation value relative to the decision maker’s psychological expectations at the corresponding time
Step 4: According to Equations (15)–(20), calculate the corresponding value functions and , decision weight functions and , .
Step 5: According to Equations (21)–(23), the cumulative prospect value of each scheme is composed of positive and negative utility prospect values .
Step 6: According to Equation (15) and Equation (22), calculate the weight of corresponding evaluation indicators .
Step 7: According to Equation (24), calculate the comprehensive cumulative prospect value for each option, sort the decision options based on the value, and take .
Figure 1 describes the dynamic decision-making process that takes into account the psychological expectations of decision makers: